Mats Bengtsson Heat saving calculations and house energy need

Simple form for calculating heat savings yourself

Mats Bengtsson mib over the years

A simple form for calculating heat savings yourself

The basics in the calculations are fairly simple, and the questions regarding them are common. Thus, I created this simple form to fill in some data. It delivers cost saving calculation times utilising comparisons between the alternatives. The shown alternatives are

  • Using an eletric heater only
  • Using an air/water heat pump
  • Using a geothermal heat pump

The assumption for the calculations are that the different heat pumps are enough for heating the house without addtional electric heater, or that the differences in cost from needing such additions are small enough to be neglected.

Simple input data

The below input data are to make a rough comparison. The average heat consumption is assumed to be the heat consumption needed for the heating, and assumed to be fully replaced with the alternative heat pumps. It is important to think of it not as the electricity consumption, but the needed consumption for the heating. Thus, hot water is assumed not to be included, neither household electricity.

Also, if the heating today is fully or partly produced by a heat pump or non electrical furnace, their production, if they are to be replaced, has to be translated to corresponding needed heating kwh without them before entering the kwh need.

Base heating assumptions for calculations
Average heat consumption per year (kwh)
Average COP per year using geothermal pump
Average COP per year using air/water pump

Investment costs

The investments are only divided into two different costs:

  • The total investment needed for the geothermal heating. This includes all costs, heat pump, control system, hole in the mountain, installation, ...
  • The total investment needed for the Air/Water heat pump. Again including pump, control system, installation, ...

To make the comparison meaningful, the costs should be comaprable. That means if one alternative doe notinclude costs for water heating, then the other should neither.

Base cost assumptions for calculations
Geothermal investment, including all (SEK)
air/water investment, including all (SEK)

Resulting pay back time

Below is calculated the needed times to get back the investment for the alternatives, assuming that the cost per kwh is 1 SEK.

  • The electric heater is included as worst case reference, and is thus calculated without an investment in a new electric heater.
  • The columns "Air/water Saving" and "Geothermal saving" shows the time it takes to get back the investment for respective of the alternatives, compared to keeping an electric heater. Observe that the less energy is needed fo rheating, the longer time it takes to get back profit after an investment
  • The column "Geothermal saving above Air/Water looks at the pay back time for the decision to buy a geothermal pump, compared to buying an Air/Water pump. It is thus comparing the time it takes to get back the additional investment for the geothermal pump (the difference in investment) by the improved COP produced by that pump. A more thorough explanation for the reason for doing this kind of comparison is given.
Accumulated savings for the alternatives,year for year
Year Electric Heater Cost (SEK) Air/Water Saving (SEK) Geothermal Saving (SEK) Geothermal saving above Air/Water (SEK)
1 0 0 0 0



Never trade stocks without having tested your system. In fact, most trading systems are not profitable if tested over many stocks. Full story...

Do not invest in heating equipment without having compared the alternatives, not only to current situation, but also to each other. Full story...

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