FAQ: Frequently asked questions

Documentation for the software is available on the help pages as well as in the form of YouTube videos. A comprehensive user manual is currently not available. If any questions remain unanswered, please feel free to contact our support team.

Users of nPro particularly value the ability to calculate and technically and economically compare different energy concepts within a very short time. This is especially relevant for feasibility studies and early planning phases (e.g. conceptual design).

In particular, the planning of districts with heat networks is often complex, as a large number of different buildings must be considered individually. This level of complexity is frequently not manageable with conventional simulation tools.

The goal of nPro is therefore to reduce the effort required for early-stage planning and to identify the most suitable energy concept from a wide range of possible solutions. With conventional simulation software, the time required to analyse complex district and heat network systems is significantly higher. At the same time, the benefit of highly detailed simulations in the early planning phase is often limited, as many fundamental boundary conditions are still uncertain at that stage.

nPro is commonly used in the conceptual or early planning phase of buildings and districts. Especially when boundary conditions change frequently, it is beneficial to use a flexible tool such as nPro to quickly and easily evaluate different energy supply concepts.

nPro is therefore used by energy utilities, municipal utilities, and engineering consultancies.

nPro is only suitable to a limited extent for the analysis of complex, user-defined control strategies for planned or existing systems. In such cases, other specialized software tools may be more appropriate. Furthermore, nPro does not perform heating load calculations or detailed building physics simulations.

You can test nPro free of charge for three weeks with a demo license. After the trial period ends, access to your user account will be deactivated. No costs will be incurred. You can create a demo account on the tool page.

nPro is particularly suitable for service phases 1 to 2 and partially for service phases 3 to 4, i.e. especially for basic evaluation and conceptual design (and to some extent detailed design). In these early planning phases, it is crucial to be able to quickly and easily compare different variants in order to identify the optimal energy concept.

Yes, nPro is very well suited for feasibility studies. From the generation of appropriate load profiles, through pipe network design and sizing of central energy generation units, to economic analysis and comparison of different variants, the key calculation steps of a feasibility study can be covered within nPro.

Yes, nPro can be used not only for districts but also for the planning of building energy systems (project types: “single building” or “energy hub”). However, it should be noted that the demand profiles generated by nPro are not stochastic in nature. As a result, demand profiles for individual small buildings (e.g. single-family houses, especially electricity demand) may not be represented with high accuracy. In such cases, you have the option to upload your own demand profiles.

Yes, nPro can also be used for the analysis of larger systems such as neighbourhoods, cities, or counties, provided that the energy exchange between technologies can be considered ideal, i.e. network losses (e.g. in the electricity grid) are negligible. In this context, nPro can be used, for example, for potential studies to assess the available solar thermal potential or to determine what share of the heat demand in a given area could be covered by solar thermal energy, geothermal energy, or wastewater heat.

For areas with many thousands of buildings, these can be represented as clusters of buildings (building groups), allowing even very large building stocks to be modelled efficiently.

Yes. As part of municipal heat planning, concrete implementation recommendations are typically developed for the energy supply of districts. nPro can be used within this process to identify the most suitable supply concept for a district and to assess which potentials (PV, solar thermal, etc.) can be utilised and to what extent in order to meet the district’s energy demand.

In addition, specific heat networks can be represented geographically, and the economic performance of the supply solution can be evaluated.

nPro automatically saves your project data whenever you start a new calculation (“Calculate district” or when running the sizing or simulation calculation on the energy hub page). In addition, you can manually save your project at any time by clicking the Save button (disk icon in the top left corner).

Yes, on the project overview page you can copy individual variants to other projects. However, an entire project cannot be copied as a whole (in this case, all variants can be copied individually). A proven approach is to create your own project templates and base new projects on them. This ensures that all relevant project settings – such as cost assumptions, default parameters, or project structure – are automatically transferred correctly.

No, an undo function is not yet available (this feature is planned). However, you can reload the page or the project to return to the last saved state.

Yes, multiple feed-in points for a heat network can be defined within a district. There is always one primary energy hub, and additional secondary energy hubs can be added. Considering the geographical distribution of energy hubs is particularly useful when analysing their impact on heat network sizing.

Yes, an energy hub must always be represented as a building (polygon) and therefore has to be drawn as a building. However, you can also draw a small rectangular building and set all heat demands within this building to zero, so that it serves purely as an energy hub.

A typical example is a geothermal borehole field that feeds heat into the network at a single location. In this case, you can draw the geothermal area (or a distribution shaft) as a building polygon and then define this building as an energy hub. An example of this workflow is shown in our video tutorial.

As of version 4 (Nov 2025), districts with more than 1,000 buildings can be processed. However, we recommend limiting the network size to a maximum of 1,500 to 2,000 connected buildings in order to ensure smooth usability.

How long does the simulation take?
The pure heat network simulation for a district with around 1,000 buildings typically takes only about 1 minute. Subsequent data transfer and rendering of the results in the browser require additional time and depend on the performance of the user’s computer and the internet connection.

Why does loading buildings sometimes take longer?
When loading building data (e.g. when creating a new project), building outlines, areas, and pipe geometries need to be corrected and processed. Some of these complex geometric operations are performed not on our servers, but directly in the user’s browser. The processing speed therefore depends on the performance of the local machine.

What does the message “Page is not responding” mean?
This browser message indicates that additional geometric operations are still being executed locally. This is normal and usually occurs only once during the initial creation of buildings and pipe segments. In this case, simply click “Continue” or “Wait” — the process will be completed after a short time.

Tips for large districts (> 1,000 buildings):

• Disable labels for pipes or buildings (e.g. “DN 100”) — this significantly improves map performance.
• For very large datasets, use a laptop or workstation with sufficient RAM, a modern CPU, and a fast internet connection.

In many cases, nPro can also be used to calculate large districts with more than 1,500 buildings. However, from around 1,500 buildings onwards, the user experience may become less smooth. In such cases, it is recommended to cluster the district or split it into several sub-areas.

A proven workflow is as follows:

• Divide the district into sub-areas
  Create, for example, two variants with approximately 1,000 buildings each and perform the complete calculation separately for each sub-area.
• Export load profiles at the energy hub
  After the calculation, export the hourly load profile at the respective energy hub for each sub-area.
• Create a higher-level district variant
  Create a new variant representing the entire area. For each sub-area, draw a representative building (polygon) that serves as the district connection point.
• Assign the exported profiles in the higher-level project
  Upload the previously exported load profiles to the corresponding representative building polygons (e.g. under “space heating demand”). These profiles include both the building demands and the network losses of the respective sub-area.
• Size and simulate the energy hub in the main project
  The central energy hub is now simulated and sized within the higher-level variant.
• Complete the economic assessment
  The costs of the sub-areas (e.g. local distribution networks, structural measures, storage systems, pumps) can be added in the main project under “Other costs”.

This approach makes it possible to realistically model very large areas while keeping the calculations efficient.

For heat network calculations, nPro uses a quasi-static calculation approach with an hourly resolution. In virtually all cases, this approach is sufficiently detailed for the calculation of heat network losses. Heat loss calculations are performed based on DIN EN 13941.

nPro currently does not support thermo-hydraulic network simulations in which all thermodynamic state variables are modelled in a fully coupled manner (e.g. enthalpies and pressures). However, such analyses typically become relevant only—if at all—for highly complex systems and detailed engineering studies.

No, at present only non-meshed (radial) heat networks can be simulated in nPro. However, support for meshed networks is planned for one of the upcoming versions.

No, currently (as of Dec 2025) each energy hub has exactly one connection point. If you want to represent multiple branches for sub-networks, you can create the branching directly downstream of the building wall penetration. In this context, it can be useful to represent the energy hub building as a small, representative polygon on the map so that the pipes can approximately branch off from a single point.

The daily profiles for the different building types are based on extensive background research. A wide range of sources has been analysed, including, for example:

1. Guideline for municipal energy use planning in Bavaria
2. Official publication of rules for energy consumption values and reference values for non-residential buildings (April 2015)
3. SIA 2024
4. VDI 3807 Part 2

as well as many additional individual sources and studies. The standard load profiles are also derived from various sources. One example is the reference load profiles published by BDEW. In addition, further studies and publicly available datasets were used, such as studies on electrical load profiles, as well as our own analyses, for example the evaluation of presence profiles derived from Google Maps data.

The generation of demand profiles for space heating (and air conditioning) is primarily based on the degree-day method, i.e. a linear relationship between heat demand and outdoor air temperature is assumed. Within the tool, several approaches are available to calculate load profiles, depending on the user inputs.

Specifically for nPro, an approach has been developed that allows a customised load profile to be generated based on the peak load (kW) and the annual heat demand (MWh), ensuring that both key figures are matched. To achieve this, the degrees of freedom of the degree-day approach (e.g. heating limit temperature, setpoint temperature, etc.) are optimised so that both the peak load and the annual demand are consistent with the user inputs.

In a second step, seasonal profiles combined with daily profiles are superimposed to form a complete annual profile for space heating, domestic hot water, space cooling, process cooling, plug loads, and e-mobility.

Yes. If you already have load profiles for a specific type of energy demand (e.g. domestic hot water), you can upload them directly for a building using the import function (e.g. by copy & paste from Excel). nPro can process different time resolutions. More information can be found here.

All calculation models in nPro are based on an hourly resolution. This resolution cannot be changed; in particular, a 15-minute resolution is not available for the internal calculations.

However, when importing time series, nPro supports a wide range of different time resolutions, including daily values, hourly values, 15-minute values, and many others. A detailed overview can be found here.

Yes. The space heating demands in nPro correspond to the amount of heat that must be supplied by the generation system (e.g. condenser output of a heat pump, heat exchanger of a heat network, or heat output of an electric heater). Distribution losses within the building are already included in these values.

When entering custom demand values, it is therefore important to ensure that the values already include any internal distribution losses. This is particularly relevant for domestic hot water, which may be provided either decentrally (with negligible losses) or centrally (with potentially significant losses due to circulation piping).

The weather profiles used in nPro are sourced from the database climate.onebuilding.org. These datasets represent typical meteorological years (TMY), usually based on recent weather periods (e.g. 2000–2020) in order to reflect climatic changes as accurately as possible.

The EPW files contain hourly values such as temperature, humidity, wind speed, and solar radiation, and can also be uploaded manually into nPro if required.

Booster heat pumps at the building level are automatically installed when the heat demand of the buildings cannot be covered via a heat exchanger due to insufficient heat network temperatures.

For example, if the specified demands for domestic hot water and space heating require a supply temperature of 60 °C, a heat network supply temperature of 60 °C + 2 K = 62 °C is sufficient to cover both demands directly from the network without a booster heat pump. If, in this example, the heat network supply temperature is set to at least 62 °C, the booster heat pump will not be added automatically.

However, if the heat network supply temperature falls to less than 2 K above the building supply temperature (for at least one hour during the year), a booster heat pump will be added automatically (a warning message will be displayed).

The usable floor area is used to convert area-specific values (kWh/m² or W/m²) into absolute quantities, such as annual energy demand in MWh or peak heating load in kW.

If your kWh/m² values are based on the net floor area (NFA), you should enter the NFA as the area. If the values refer to the gross floor area (GFA), please enter the GFA accordingly. There is no additional logic associated with the area input; it is used exclusively to convert area-specific values into absolute values.

Yes, decentralised thermal storage systems can be considered for both domestic hot water and space heating. They reduce the required building connection capacity, but result in higher investment costs.

Directly uploading PDF files for building import is currently not possible, as PDF files usually do not contain georeferenced data. However, there are two possible approaches:

• You can use the free software QGIS to georeference the PDF file and export it as a Shape or GeoJSON file. These Shape or GeoJSON files may contain both building and network geometries and can be uploaded directly into nPro. The workflow is explained step by step in this video tutorial.
• Check whether the creator of the PDF file can also provide GeoJSON or Shape files, as these georeferenced formats can be imported directly into nPro. In many cases, the PDF was created using software that is also capable of exporting other georeferenced file formats.

No, at present (as of Dec 2025), nPro does not yet support the import of DWG or DXF files. However, we plan to integrate this functionality in one of the upcoming versions.

No, at present (as of Dec 2025), nPro does not yet support the import of Stanet files. However, we plan to integrate this functionality in one of the upcoming versions.

Yes, groundwater can be represented in nPro using the “heat / cold source” technology. Here, you can define both the available thermal capacity (e.g. based on the yield of the source) and the temperature of the heat source. If required, this information can also be provided as a time-resolved profile. In this way, the use of groundwater as a heat source can be modelled realistically.

In the sizing calculation for the energy hub, the generation units are, by default, sized in such a way that the maximum load can be covered by the generators alone (without using thermal storage). This means that if the maximum heating load is 100 kW, the capacities of, for example, a biomass boiler and a gas boiler would be dimensioned so that their combined capacity is at least 100 kW.

The reason for this approach is that, under a conservative design philosophy, it is not assumed that the thermal storage is charged at the time of peak heating demand. Especially in the case of heat pumps, however, it can be beneficial to use the thermal storage for peak load coverage. This can be implemented in nPro by disabling the option “Conservative system design” in the sizing calculation settings.

In nPro, system operation is determined by the selected objective function (typically minimum annual costs) rather than by predefined, control-engineering–based “intuitive” operating strategies. As a result, it may occur that a large seasonal storage is not fully charged at the beginning of summer—even if sufficient solar thermal capacity would be available.

The reason is as follows: If the storage is small relative to the available generation capacity, it can be fully charged within just a few sunny days. The optimisation model has full knowledge of the entire weather year and therefore “knows” in early summer that many additional sunny days will still follow. Consequently, the storage is charged only to the extent required to meet the heat demand in the subsequent days, as a fully charged storage would lead to higher heat losses.

Only towards the end of the warm season (e.g. October/November), when it becomes clear that few sunny days remain, is the storage typically fully charged in the simulation. From a purely economic perspective, this operating strategy is optimal, but from a control-engineering perspective it is not always intuitive. However, the simulated result represents the most cost-efficient mode of operation and does not differ in terms of global key figures (gas consumption, electricity costs, etc.) from a more intuitive operating behaviour (whether excess heat is unused in spring or in autumn is irrelevant for the annual balance). We are nevertheless working on representing this aspect of system operation for seasonal thermal storage systems in a more realistic way in future versions of nPro.

Yes, blocking periods can be represented using a custom operating restriction profile in the heat pump settings. To do so, define an hourly profile (e.g. 24 values such as “1, 1, 0, 1, …”) to block operation during specific hours.

Losses during defrosting operation are not modelled explicitly in nPro. However, they can be taken into account in an aggregated way by adjusting the COP, depending on the calculation method used (e.g. Carnot model, performance data table, etc.).

The sizing optimisation in nPro is based on typical design days. This means that a limited number of days are selected from the full year that represent the annual behaviour as accurately as possible. Depending on the complexity of the energy system, nPro typically uses up to 60 typical design days for the calculation.

Using typical design days reduces computational effort and simulation time. For very complex energy systems, for example those with seasonal thermal storage, it may be useful to manually increase the number of typical design days, e.g. to 100. The maximum possible number of typical design days is 365.

Please note that, unlike the sizing optimisation (first calculation step), the operational simulation (second calculation step) always uses the full hourly resolution of the year (365 days with 8,760 time steps).

Yes, custom component models can be defined for certain technologies. Currently, this is supported for heat pumps, solar thermal collectors, and PVT collectors. For all other technologies, the general model parameters can be adjusted for the respective use case, such as the electrical or thermal efficiency of a boiler or CHP unit.

Yes, you can upload time-resolved electricity price profiles as time series in the electricity grid settings. These profiles are then considered on an hourly basis in the optimisation and can, for example, influence the sizing of thermal storage systems or heat pumps. Variable profiles can also be defined for feed-in tariffs and for the specific CO₂ emissions of imported or exported electricity.

In the sizing optimisation, the system components are dimensioned in such a way that the selected objective function—typically the minimisation of total annual costs—is achieved. This is based on a full cost calculation using the net present value method, including residual values and replacement investments in accordance with VDI 2067.

The optimisation is based on a mathematical optimisation model, either a linear programming (LP) model or a mixed-integer linear programming (MILP) model. More information on the optimisation approach can be found on the pages describing our research activities and in the documentation.

Yes, non-predefined fuels can also be represented in the simulation. To do so, you can redefine an existing energy carrier—for example, treating biomass as heating oil— and adjust the three fuel parameters: specific CO₂ emissions, primary energy factor, and purchase price to match those of the desired fuel.

This approach is possible because the simulation balances energy quantities (kWh) and does not explicitly model fuel-specific physical properties (such as viscosity).

No, the optimisation algorithms and simulation models are not open source.

An energy hub refers to the central energy supply unit of a district, a building, or another type of energy system. This can be a central heating plant, but also, for example, an air-source heat pump located in the basement of a building.

In the case of a heat network, the central heat generators or heat sources are part of the energy hub. In a cold district heating network with a geothermal borehole field, the geothermal field would be part of the energy hub, whereas the decentralised heat pumps would be defined within the individual buildings rather than in the energy hub.

Yes, you can upload a custom, hourly resolved generation profile in the settings for photovoltaics, solar thermal, PVT, or wind power. This can be useful if you have created generation profiles using other software tools and would like to use them instead of the profiles calculated internally by nPro.

By default, economic performance is used as the objective function. The optimisation therefore identifies the cost-optimal energy system that is able to fully cover the specified energy demands while resulting in the lowest total costs.

The optimisation objective is based on the total system costs in accordance with VDI 2067 (full cost approach, including annualised investments with replacement investments and residual values). In addition, alternative optimisation objectives such as minimising electricity imports or minimising CO₂ emissions can be selected.

In the operational simulation, a cost-optimal operating strategy of the system components is always assumed. More information on the optimisation approach can be found in the optimisation model documentation .

Various optimisation objectives can be selected in the energy hub settings. These include:

1. Total annual costs: The net present value of the overall system is minimised.
2. Multi-objective optimisation: costs and CO₂ emissions: Multiple system designs are determined for different CO₂ price levels.
3. CO₂ emissions: The annual CO₂ emissions of the system are minimised. This may lead to highly uneconomic systems, as emissions alone are used as the optimisation criterion.
4. Electricity import from the grid: The annual electricity import from the public grid is minimised.

Indirectly, yes. By adding a thermal storage system and disabling the “Conservative system design” option, the optimisation will select a smaller heat pump capacity and use the thermal storage to cover peak loads.

In addition, introducing an additional peak load heat generator (e.g. electric heater, boiler, etc.) can further reduce the required heat pump capacity.

When the “Conservative system design” option is enabled, the energy system is sized in such a way that the maximum occurring energy demands can be covered exclusively by the installed generation units. Thermal storage systems are not considered for load coverage, as it is assumed that they are fully depleted during the hour of peak demand.

This can be disadvantageous when a heat pump is operated together with a thermal storage system and an intelligent control strategy (e.g. predictive control) is able to charge the storage ahead of a peak load. In such cases, the heat pump could be sized smaller.

Whether this option should be enabled therefore strongly depends on the intended control strategy. For systems with intelligent control, it can often be disabled in order to reduce generator sizes and use thermal storage for peak load coverage.

Yes. If, in a given hour, the electricity purchase price is lower than the feed-in tariff, this currently leads to a model-induced behaviour in the optimisation: for economic reasons, the model would assume that electricity is purchased cheaply and simultaneously fed into the grid at a higher price.

To avoid this behaviour, you should ensure that the electricity purchase price is never lower than the feed-in tariff in any hour.

An alternative solution is to use the direct feed-in option for photovoltaic systems or CHP units. In this case, you can define a feed-in remuneration that may also be higher than the electricity purchase price (hourly profiles can be uploaded as well).

Yes. A hydrogen CHP unit can be represented using the fuel cell model. If waste heat utilisation is enabled, this unit generates both heat and electricity, similar to a conventional CHP unit. The ratio between heat and electricity production is defined via the electrical and thermal efficiencies.

A hydrogen boiler can be represented using the standard boiler models by selecting an existing energy carrier (e.g. biogas) and adjusting its parameters (CO₂ factors, primary energy factors, and prices) to those of hydrogen.

This approach is possible because the boiler model implemented in nPro is relatively simple and converts 1 kWh of fuel into 0.x kWh of heat according to the specified thermal efficiency.

If you want to directly influence the sizing of system components, you can define manual capacity limits. You can specify a lower and/or upper bound for the capacity. If you want to fix the capacity of a technology to a specific value, simply set both the lower and upper bounds to that value. In this case, the component capacity is no longer determined by the optimisation, but is predefined by the user.

The sizing calculation is based on a limited number of time steps using typical days. This means that not all 8,760 hourly time steps of the year are considered, but only a set of representative typical days (usually between 20 and 60).

In contrast, the operational simulation is performed for the full year with all 8,760 hourly time steps. As a result, operational key figures may differ from those obtained in the sizing calculation.

You have no direct influence on the cycling behaviour of the units in the simulation. Since cycling is not economically priced (e.g. start-up or shut-down costs), this behaviour is not taken into account in the optimisation.

In nPro, a maximum of two boiler technologies can be selected simultaneously, for example a gas boiler and a biomass boiler. More than two boilers or CHP units (e.g. three gas boilers) cannot be represented explicitly, as nPro performs the sizing based on technologies rather than on individual components.

This means that multiple units of the same technology lead to the same calculation result as a single, aggregated generation capacity.

This is also due to the fact that nPro uses an idealised operating model, in which boilers and CHP units can modulate continuously between 0 and 100 %, and effects such as part-load efficiencies or start-up costs are not taken into account.

Further details can be found in our publication:
Design optimization of multi-energy systems using mixed-integer linear programming: Which model complexity and level of detail is sufficient?
M. Wirtz, M. Hahn, T. Schreiber, D. Müller. Energy Conversion and Management, 240, 114249, 2021.

Yes, solar air collectors can be represented using the solar thermal model. You can either use the predefined solar air collector module or define custom collector models in accordance with ISO 9806.

Alternatively, you can upload custom generation profiles, for example generated using other software tools. In this case, the profiles are used directly in the sizing calculation and are not calculated internally by nPro.

An extraction rate of 50 W/m is generally only realistic for fields with a small number of boreholes. For larger borehole fields, such values are usually too optimistic and typically lie in the range of approximately 15–25 W/m, depending on the boundary conditions.

There are several levers to influence the extraction rate per metre of borehole:

• Adjust the minimum inlet temperature: The lower the permissible minimum brine temperature at the borehole inlet, the higher the achievable extraction rate.
• Reduce the design period: A design horizon of, for example, 50 years is quite conservative and limits the allowable extraction rate. Shorter design periods lead to higher extraction rates per metre of borehole.
• Increase borehole spacing: Larger distances between boreholes reduce thermal interference and increase the possible extraction rate per metre.
• Optimise the field geometry: Instead of a nearly square field (e.g. 14 × 16 boreholes), an elongated layout (e.g. 4 × 50) can be advantageous, as more heat can flow in from the surrounding ground.
• Include regeneration: If summer cooling loads are rejected via the borehole field, this increases the amount of heat that can be extracted annually.

Yes, modelling can be carried out in several ways:

• using the air-source heat pump or compression chiller model (with appropriately high COP values, so that the electricity demand essentially represents the circulation pump power),
• using the solar thermal model with adapted ISO 9806 parameters for a custom collector type, or
• using the heat / cold source model, if a specific hourly generation profile is already available.

These approaches allow different operating modes of air heat exchangers to be represented in a flexible manner.

No, a self-sufficiency level cannot be specified directly.

However, you can manually limit electricity imports (MWh/year) or select the optimisation objective “minimise electricity imports”. This will increase the level of self-sufficiency indirectly.

The cost parameters are based on various sources, including VDI 2067, as well as internal estimates. The values provided in nPro do not claim to be accurate or complete. If you have your own cost data, you can enter these values directly in the software.

Good reference sources for cost parameters include the technology catalogue for municipal heat planning of the State of Baden-Württemberg and the technology catalogue of the Competence Center for Municipal Heat Transition .

Yes, a range of funding and subsidy mechanisms can be considered in nPro. These include, for example, investment subsidies that can be defined on a technology-specific basis for building-level systems (e.g. heat substations, booster heat pumps), for the heat network, and for systems in the energy hub.

The BEW operating cost subsidy for solar thermal systems and large-scale heat pumps can be represented directly. In addition, feed-in tariffs and incentives for self-consumed electricity can be defined in detail for photovoltaics, combined heat and power units, wind power, and hydropower.

Funding mechanisms that cannot be represented directly in nPro can usually still be taken into account in the economic assessment by applying suitable workarounds.

The economic assessment is essentially based on the German standard VDI 2067, which corresponds to a net present value (NPV) approach. Future cash flows are discounted back to the investment year (year 0). Replacement investments after the end of a component’s lifetime as well as residual values at the end of the project period are taken into account.

This is a question many new users ask—and rightly so. We address it through the following points:

1. Extensive practical use: nPro is used on a daily basis by a large number of companies (approximately 150 active users per day). The high volume of simulations helps ensure that potential calculation errors are identified quickly and that a high level of software quality is maintained over time.
2. Continuous testing and validation: We continuously test and validate the calculation results. Many critical calculation steps can be validated in great detail using real-world data, for example generation profiles for solar thermal, photovoltaics, or PVT systems.
3. Transparent modelling approaches: In many parts of the software, we use simple and transparent calculation models that do not require complex validation. One example is the boiler model, which is essentially based on a straightforward energy balance.
4. Traceability of results: The software displays intermediate results in as much detail as possible, allowing users to understand and trace calculation steps and underlying assumptions.
5. Transparent handling of errors: Known software issues are published transparently on our website and are resolved—depending on their severity—promptly or immediately. In the case of critical issues, users are actively informed.

Many of the calculation steps implemented in nPro have been validated against established tools or standards, including energyPRO.

Simulation steps that cannot be validated directly have been extensively tested and plausibility-checked using different approaches. Among the most thoroughly validated models are, for example:

• Generation profiles for solar thermal systems
• Photovoltaic systems
• PVT systems
• Building demand simulation

In addition, the sizing optimisation has been compared with sizing decisions made by external engineers. A fully objective validation, however, is not possible, as the “true” techno-economic optimum of real-world systems is not mathematically well-defined.

Yes, the simulation results for numerous real-world projects have been compared— in some cases comprehensively, in others selectively—with actual measurement and operational data. This validation process is inherently ongoing and is continuously expanded in order to further improve the accuracy of the simulations.

All relevant information on IT security can be found in our IT security concept (status: November 2025).

In addition, the terms and conditions (which are included with every offer) contain important information on data protection as well as a data processing agreement (DPA) in the appendix. If you have any further questions, our support team will be happy to assist you.

Yes, the servers used by nPro are located in Germany. The data centre location is Frankfurt am Main.

Yes, starting with version 4 (November 2025), single sign-on (SSO) via Microsoft (Entra ID) is available.

Yes, nPro Energy is fully economically independent. There are no financial or economic dependencies on other companies or institutions.

Yes, the entire nPro software is developed 100 % in-house. This ensures a high level of quality control, rapid development of new features, and seamless integration of all software components.

Data security is of utmost importance to us, as users enter sensitive project data into the tool. We therefore place a strong emphasis on the security of our systems and, where appropriate, engage external developers and consultants to ensure long-term and reliable data security.

nPro uses two independent and redundant backup systems for data protection:

• Daily backups performed by the IT infrastructure provider, enabling the restoration of all server data.
• In addition, daily backups of project and user data to a separate commercial cloud system.

All project data that are older than one day (and therefore included in the daily backup) are redundantly protected against data loss.

Access to project data is strictly limited to the user, unless the user explicitly shares the project.

For support purposes, a project can be deliberately shared with an nPro employee. In rare exceptional cases, the nPro software development team may access data solely to maintain critical IT services or upon explicit request by the customer.

Yes, nPro Energy complies with German data protection regulations. The entire server infrastructure is located within the sovereign territory of the Federal Republic of Germany, currently in a data centre in Frankfurt am Main.

No, user licences are assigned to individual persons. We currently do not offer a company-wide or floating licence.

Please purchase a personal single-user licence for each user who works with the tool. The pricing is designed accordingly and is fair and transparent.

nPro monitors licence usage through technical and organisational measures and reserves the right to take action in the event of violations of the licence terms.

Yes, you can increase the number of licences at any time. Existing licences are credited on a pro-rata monthly basis for the remaining usage period and deducted from the price of the new order. To extend your licence quantity, please contact our support team.

The usage fee is invoiced in advance for the selected subscription period. You will receive an invoice accordingly. Payment can be made by bank transfer or credit card.

There are two options:

Licence without subscription (no automatic renewal):

• The licence is valid for a fixed period (for existing customers: at least 12 months).
• Therefore, no cancellation is required.
• If you wish to continue using the licence after it expires, you must actively initiate the renewal.

Optional: Subscription (with automatic renewal):

• To simplify annual renewals, you may choose a licence with automatic renewal.
• The licence is also valid for a fixed period (for existing customers: at least 12 months). Upon expiry, it is automatically renewed for a further 12 months.
• You may cancel the automatic renewal at any time up to 14 days before the end of the current term by email.

In both cases, invoicing is carried out at the beginning of the term for the full usage period.

Yes, all nPro software updates are included at no additional cost and are provided automatically.

The conversion is carried out immediately. If you enter the email address of your demo account in the order form, the account is automatically and instantly converted into a commercial account upon completion of the order. All projects and settings remain fully preserved.

You have three options to transfer your licence and projects:

• Direct account transfer:
  Simply change the email address in the user settings to your colleague’s email address (and update the password accordingly).
  Advantage: All projects and project shares remain fully intact.
• Create a new account:
  Your colleague can create their own account, and we can transfer the licence upon request. You can then share selected variants or projects with them. They may optionally create a copy of these projects (e.g. by copying a variant into a new project).
• Manual transfer by nPro:
  Upon request, we can also transfer projects manually to another account. This involves manual effort and may take several days. Please contact us by email if you would like to use this option.

Yes, we provide free technical support for users with a demo or commercial licence to assist with the use of the software. Support is available via email or telephone; video calls can also be arranged if required.

For up to 10 users, you can simply use our order page. After submitting the form, you will receive a PDF invoice, which can be paid by bank transfer or credit card.

Orders can also be placed by email at info@npro.energy.

For larger teams or special requirements, please contact us by email. We will then prepare an individual offer, including customised terms and conditions if required.

You can pay by bank transfer or credit card. The details for bank transfer are provided on the invoice.

Yes, this is possible. For new customers, we offer the option to initially order nPro for a period of less than 12 months (see the order page).

In addition, a free 3-week demo licence is available.

For most of our customers, nPro already pays for itself if the software saves just two working hours per month.

Current pricing is available on our order page.

The nPro licence model is designed as a prepaid model: licences are purchased for a defined period, and pausing the licence is not possible.

For the initial order, we currently (as of December 2025) offer a 10% new customer discount, and you may choose a flexible term, for example 6 months.

For subsequent renewals, the minimum term is 12 months. Further details can be found on the order page.

Yes, academic users may generally use nPro free of charge for research purposes.

This explicitly does not include commercial contract research or consulting services for companies. Further details can be found in the terms of use.

nPro reserves the right to take legal action and, where applicable, claim damages in the event of violations of the licence terms.

No, no formal proof is required during the registration process.

You simply register using the academic licence, with the understanding that the terms of use are complied with.

We reserve the right to verify compliance with these conditions on a random basis and to take appropriate action in the event of violations.

Yes, the academic licence may be used provided that nPro is used exclusively for the academic thesis. Not permitted is the use of the academic licence if, as part of the cooperation, additional activities are carried out for the company that are not directly related to the thesis—for example commercial consulting, project work, or contract research. In such cases, a commercial licence is required. Further details can be found in the terms of use.

Yes, nPro is regularly involved in publicly funded research projects. If you are planning a project and are looking for a project partner in the fields of districts, heat networks, and/or software, please feel free to contact us. We also support the application process with our experience and expertise.

We are working towards making as many nPro calculation functions as possible available in a modular way via an API. This would allow you, for example, to integrate functions such as the generation of heat demand profiles or PVT generation profiles into your own in-house tools.

However, as of December 2025, no API is available, and none is planned for 2026.

nPro has a broad base of calculation and simulation algorithms— ranging from the generation of load profiles to solar thermal and PVT calculations, as well as complex optimisation algorithms. Do you need source code for a solar thermal calculation in accordance with ISO 9806? A PVT collector model? Or would you like to use parts of our optimisation algorithms? Feel free to contact us.

We only provide support for planning projects in exceptional cases. Our primary focus is on the development and operation of the nPro software. However, we are happy to recommend qualified planning and engineering offices. Please contact us by email if you are interested.

As of January 2026, more than 400 companies have purchased a commercial licence for the nPro software. The number of active users is approximately 120–180 per day. A selection of our customers can be found on our references page.

Our customers come from the fields of energy supply, engineering and planning offices, architecture, research & development, municipalities/cities, and industry. Most users are based in Germany, but nPro is also used in Austria, Switzerland, the Netherlands, Spain, Italy, France, Belgium, Denmark, Ireland, North Macedonia, Greece, as well as overseas (including Canada, the USA, and South Korea).

Yes, nPro Energy is fully economically independent. There are no financial or economic dependencies on other companies or institutions.

nPro Energy was founded in 2022 as a spin-off from RWTH Aachen University by Dr.-Ing. Marco Wirtz. The goal of the start-up is to develop a planning software that enables engineers and planners to quickly and efficiently simulate and size energy systems for buildings and districts. Further information can be found on our About us page.

To use nPro, an internet connection is required. No installation or administrator rights are necessary. Software updates are applied automatically. For large districts with more than 1,000 buildings, a powerful computer (e.g. at least 16 GB of RAM and a modern processor) can be beneficial to ensure smooth operation.

Yes, a continuous internet connection is required to use nPro. An unstable connection may lead to issues during operation.

Software updates are provided automatically via the internet. This ensures that you are always using the latest version of nPro. Updates either extend the range of functions or fix software bugs.

No, nPro can be used without installation. All you need is an internet browser (e.g. Chrome, Firefox, or Safari) and an internet connection.

nPro officially supports Chrome, Firefox, and Safari. Other common browsers usually work without issues as well. If you experience any problems, please feel free to contact us.

If nPro crashes after only a few clicks and a white screen appears, this may be caused by a browser add-on (e.g. in Chrome or Firefox)— most commonly the "Google Translate" add-on. Please disable or uninstall this add-on, use a different browser, or open a “private window” (Firefox) or “incognito window” (Chrome).

If the issue persists, please contact us.