Your Heating System Calculator

Objectively compare heating systems for your existing building over their entire operating life and draw conclusions about actual costs and environmental performance.

This heat cost comparison tool, or the technical and economical default values it contains, applies to existing residential buildings from single-family houses to block of flats with up to 1,000 m² of living space or an annual final energy demand of up to 200,000 kWh (e.g. 20,000 l/a heating oil), respectively.

When looking for a new heating system, there are many things to consider:

- What technologies and fuels are available?
- Which subsidy programs can be used and how does that affect the investment costs?
- What about the cost of heating when I look at more than just the initial cost?

This calculator shows you on the basis of the annual full costs. It should help you to find the best solution for your house together with your energy consultant or your installer.

Basic info about house and heating system

How much energy does your house need? What about the building services?
How do you prepare your hot water?
With your information we will check which alternatives to the existing heating system are suitable for your building.

  • Existing building


  • 0-500m
  • 500-1000m
  • 1000-1500m

Your heated living space




Heat distribution

  • Central heating (with distribution system)
  • Oven (without distribution system)

Your existing heating system

Selection Icon Please choose ...
  • Oil Icon Oil boiler
  • Oil Icon Oil oven
  • Gas Icon Gas boiler
  • Gas Icon Liquefied gas oven
  • Gas Icon Gas heater
  • Air heat pump Icon Air heat pump
  • Groundwater heat pump Icon Groundwater heat pump
  • Geothermal heat pump Icon Geothermal heat pump
  • Collector heat pump Icon Collector heat pump
  • Log wood heater Icon Log wood boiler
  • Wood stove Icon Wood stove
  • Tiled stove Icon Tiled stove
  • Coal Icon Coal boiler
  • Pellets Icon Pellets boiler
  • Pellets oven Icon Pellet stove
  • Heating plant Icon District or local heating grid
  • Woodchips Icon Woodchips boiler
  • Liquified gas Icon Liquified gas boiler
  • Electric heater Icon Infrared or direct electric heating
  • Electric single heating Icon Electricty heating

Consumption of your heating


Age of your heating


Additional tiled stove / wood stove installed?

  • No Icon
  • Yes Icon

Amount of wood

m³ per year (Wood)

Existing heat release system

  • Radiator high temperature Icon
    Radiator (high temperature)
  • Radiator low temperature Icon
    Radiator (low temperature)
  • Underfloor heating Icon
    Underfloor heating
  • Combined Icon

New hot water system

  • Always with heating system
    Always with heating system
  • In winter with heating system
    In winter with heating system
  • Never with heating system
    Never with heating system

Is there already an existing thermal solar system?

  • No Icon
  • Yes Icon

Free roof area (in S, W, E direction) for photovoltaic.


You could use this free space for the installation of a photovoltaic system. You calculate about 5-6 m2 per kWp system output.
A typical 3 to 4-person household can generate as much electricity with 4 kWp (in southern countries the yield is higher) as it consumes on average per year. Usually, with this PV system size and typical consumption behavior, such a household can use approx. 20-30% of the electricity produced in the house itself. By heating water with an electric heating element or a hot-water heat pump and selective shifts in electricity use, this value can be increased to a good 50%, and with a battery to up to 80%. If you are considering buying an e-car or a heat pump for heating or - in general, if you want to do something effective against the climate crisis - it makes sense to use as much roof surface as possible for PV.

Unfortunately, the remaining roof area is too small for a sensible size of the photovoltaic system. Perhaps you have the opportunity to participate in a photovoltaic system in your area as a citizen.


New solar heating system

  • None
  • Hot water
    Hot water
  • Hot water + Heating system 15%
    Hot water + Heat. sys. 15%
  • Hot water + Heating system 25%
    Hot water + Heat. sys. 25%

Heating degree days


Standard outside temperature


Heating capacity (main heating system)

Confirm details
Basic conditions

With this information, the "Replace" tool excludes alternatives that cannot be used at all.


Connection option for local or district heating?

  • No Icon
  • Yes Icon

Access for pellet tankers and pellet storage room possible?

  • No Icon
  • Yes Icon

Is there a storage place for firewood?

  • No Icon
  • Yes Icon
Confirm details

CO2 price

EU Logo

This project receives funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 847087.
Any communication activity related to the action reflects only the author's view.
The European Union and its European Climate, Infrastructure and Environment Executive Agency (CINEA) are not responsible for any use that may be made of the information any communication activity contains.

The REPLACE consortium members shall have no liability for damages of any kind including, without limitation, direct, special, indirect, or consequential damages that may result from the use of these materials.
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Imprint Icon


General information

This calculator is designed to help you switch from an old heating system to a sustainable and more ecological heating system.
Using your details about the building, the location and the heat delivery system, your approximate heating energy requirements are calculated and a comparison of several suitable alternative heating systems is displayed.

The order is based on the information and calculations about your house (energy consumption, heat delivery system, flow temperature) and according to the carbon dioxide emissions caused. These are mainly responsible for the accelerated climate change.

An essential part of the calculation is the economic full cost comparison over 20 years. In addition to the purchase costs for the heating system, all necessary running costs, such as fuel costs, service and repair costs, are included in the calculation, taking into account inflation and energy price increases. This makes it very easy to compare several heating systems. Since the subsidies make a decisive contribution to the greening of heating systems, the current subsidies from the federal government and your state are displayed. These are also already taken into account in the calculation of investment costs and full costs.

Important notes

The values shown are generated automatically and do not replace expert advice. They are estimates of energy, operating and investment costs. The actual costs may differ from the automatically calculated values. Likewise, the calculator does not make any statements about which heating systems can be approved at your location.
The calculated subsidies from the states and the federal government are partly subject to conditions. They can change continuously. Therefore, check with your installer, energy consultant or energy advice center. Other subsidies (e.g. from the municipalities) are not taken into account.

Further information

Neutral and product-independent information: Programm klimaaktiv
Overview of subsidies in Austria, subsidy database of the Austrian Energy Agency: Förderdatenbank
Online tool for planning an efficient heat pump system: Machvier
The right heating for my house: Heizungsmatrix
Energy advice centers of the federal states: Energieberatung


Information and disclaimer

This tool is based on the Austrian “Hexit” tool ( covering the nine provinces of Austria. The Hexit tool was created by the Energy Institute Vorarlberg for the Austrian climate protection initiative “klimaaktiv” of the Federal Ministry for Climate Protection, Environment, Energy, Mobility, Innovation and Technology (BMK). This tool has been further adapted regarding functionalities and an applicability for nine European countries for the European Horizon 2020 project REPLACE ( The result is the “REPACE Your Heating System Calculator”.

This tool is a sample calculation and cannot replace a consultation. The conditions prevailing in individual cases can be very different. Deviations in positive as well as in negative direction are possible. A purchase decision should only be made on the basis of real offers.

All contents and suggestions have been compiled with the utmost care. However, no liability can be assumed for the correctness, completeness and topicality of this content by the parties involved in the creation of the tool and its content. In addition, liability - for all parties responsible for the creation of this tool - for all damage, in particular for direct or indirect as well as material or immaterial damage caused by the use or non-use of the information provided, is excluded. This relates also for cases where the REPLACE calculator is used in the form of a white label tool by third parties for consultancy or any other business, e.g. by planning offices, energy advisers or installers, etc; independently if default values or own project specific values inserted into the tool are used. The same applies analogously to the European Commission, which financed the creation of the tool, the Austrian Federal Ministry for Climate Protection (BMK), which offered to build on the forerunner tool Hexit, and the Energy Institute Vorarlberg, which developed and will host the REPLACE calculator until 30. Nov. 2025.

The results of the users are only for orientation and do not represent an expert opinion or proof towards authorities or third parties. The technical features and functionalities of the calculator are maintained and updated by Energy Institute Vorarlberg. The text and default values contained in the countries-sections of the calculator are maintained and updated by the respective beneficiaries of the REPLACE project until Oct. 2022. The logos of the respective partners are shown at the beginning of tool usage, when choosing the country of interest. In Austria the Energy Institute Vorarlberg is updating the default values for all Austrian provinces until Oct. 2022.

All prices included may be subject to temporal and local fluctuations. Subsidies may vary from municipality to municipality, from province to province and country to country, which is why the responsible authority should be contacted before making a purchase decision.

Enquiries to:

Tool developer:
Energy Institute Vorarlberg, Stadtstraße 33 / Campus V,
A-6850 Dornbirn, Dieter Bischof, E-Mail

All information about the imprint can be found here.

Replace Project Coordination:
Austrian Energy Agency, Mariahilfer Straße 136,
A-1150 Vienna, Herbert Tretter, E-Mail

All information about the imprint can be found here.

Privacy Policy:
You can download the privacy policy according to DSGVO in its current version here.

Picture credits:
Andrew Rybalko -