thermodynamic heating, heat pump: financial and ecological balance

Is thermodynamic heating, heat pumps and geothermal energy an ecologically and economically acceptable solution?

Article freely inspired by the reflections of this topic

This article concerns thermodynamic heating, very "fashionable", especially for individuals who are wondering about the choice of their future means of heating because the information that circulates is quite vague ... The purpose of this article is to see clearer.

Indeed; provided that the heat pump is powered by a renewable source installed in your home (wind, photovoltaic ...) or by 100% green electricity (green contract), thermodynamic heating is far from being as clean as pretends!

It is, for example, untrue to speak of 100% renewable or 100% green or even free energy in connection with geothermal energy. This is what we can still read too often in many commercial documents.

Here is why: in France, electricity has a primary energy cost of 2.58 times the final consumer energy. Thus, for 1 kWh spent, it would have been necessary to spend 2.58 kWh at the source. Thus a heat pump which will consume 1 kWh will in fact consume 2.58 kWh in primary energy if we wanted to compare it to a gas or oil boiler.

Here are the different correction coefficients primary energy / final energy according to the different labels: RT2005, Minergie, Effinergie and Passive House.

Points to reflect on the choice of thermodynamic heating (water-water, ground-water, air-water, air-air, etc. heat pumps)

Some points of reflection for those who "hesitate" on the choice of their heating currently:

A) By switching from an oil boiler to a heat pump, your electricity bill may be multiplied by… a certain coefficient! We understand better the promotion made by EdF and the electricity sellers for this solution!

A heat pump is not economical for your electricity bills.

B) If your electricity is produced from coal or fuel oil, the overall yield on CO2 can be of the same level as with an oil boiler taking into account the yields of thermal power plants, line losses and COP of your heat pump.

Here are CO2 releases per kWh for several European countries.

Read also: Reversible air conditioning, an ecological solution?

Concrete example:

- Oil heating. 2.6 kg of CO2 per liter of fuel oil consumed for approximately 8.5 kWh of heat (85% efficiency).
CO2 releases: 2.6 / 8.5 = 0.3 kg / kWh heat.

- Heating by heat pump in Germany (little nuclear): 0,60 kg CO2 / kWh el. If we have an average COP over the year of 2.5. CO2 rejection: 0.6 / 2.5 = 0.24 kG / kWh heat

The gain on CO2 in this case is therefore very low (20%) and the average COP over the year must actually be 2.5. If it is less than 2, an oil boiler becomes cleaner!

A heat pump powered by an oil or coal plant is not clean with regard to CO2

C) If your electricity is nuclear, you will certainly reduce much more your CO2 emissions but you finance the maintenance and revival of the French nuclear fleet.

A heat pump finances and promotes the development of nuclear power or the construction of new power plants (gas, coal) for power peaks, is it environmentally friendly?

D) The maintenance costs are high and to add to your electric bill: 2 to 300 € per year or all 2 years!

A heat pump has a high maintenance cost. This should be taken into account in the financial statement.

E) The return on investment (in the event of renovation) is generally 10 to 20 years without correction of the price of electricity which will necessarily go up. The works (horizontal soil-water, vertical drilling, etc.) are quite substantial in the event of renovation and generally very heavy financially.

Financial risk is important

Read also: Hemp insulation

F) The performances given by the installers are generally the optimal laboratory performances (like the consumption given by the car manufacturers rarely achieved in real use…)

Actual performance will be below announced performance

G) The life of the equipment is limited: there are not many refrigerators that last 30 years. However, a heat pump is an inverted fridge, it is a complex system presenting moving parts and fluids which can "wear out" ... This goes against a saying well known to building professionals: more it's simple the longer it lasts.

A heat pump has a limited lifespan compared to other heating equipment, especially considering the installation costs!

H) In the event of a horizontal collector, the deposit is not infinite since you are cooling your garden. And in some cases it can be annoying, for example, when there is snow cover! Geothermal, surface energy is indirect solar energy! The average volume heat capacity of the earth is equivalent to that of water… This remark is even more true with Air-X heat pumps: many freeze and no longer operate below 0 ° C (even if there are less and less).

Heat pumps are more sensitive than other means of heating to the weather

I) The development of thermodynamic heating (replacing gas or oil boilers) contributes to power peaks on the electrical network. These power peaks are very bad for the environment in France and greatly increase CO2 emissions. See the figures of CO2 emissions in France following the use of electricity.

The advantages of thermodynamic heating

To finish all the same on good points, there are certain advantages to thermodynamic heating, here are a few…

A) In the case of a water-X heat pump, i.e. a vertical deposit (drawing from the water table) the hot spring is much more constant than the air or the soil in your garden. But to do this, one must be "well" placed geographically and the cost of drilling is important!

Read also: Wood heating, why choose this ecological, economical and sustainable?

B) Compared to conventional electric heating (convectors), geothermal heating is much more efficient econologically!

But we must also compare the costs of return on investment. Convectors at 30 €, a DHW tank at 200 € is a house with heating for 2000 €. It's 10 € less than a small heat pump…

C) One heating with reversible air-to-air air conditioning is the most interesting to replace convectors because the investment cost is much lower ... but watch out for low temperature performance! Air-to-air heat pump heating is very interesting in addition to another heating!

D) Geothermal allows low temperature heating therefore the "overall" efficiency of the installation will be higher but low temperature heating is possible with any other heat source provided that the installation is well done!


Thermodynamic heating has many constraints and disadvantages (and there are others other than those discussed in this article, for example, we did not talk about the noise of heat pumps, here is an example with a CIAT Caléo) which are, of course, not put forward by sellers and installers.

The development of thermodynamic heating is being pushed by electricity producers who see here an economic boon. Exactly as electric heating was (and is still partly so since more than 2 million new homes have been heated in France with electricity since 2000)…

However, thermodynamic heating is a real ecological and economic advance when it precisely replaces this direct electric heating.

For any investment, it is necessary to make the balance sheet and to inquire before, our forums can help you ask your questions!

Forum heating and thermal comfort
Comparison of a professional study. Heat pump VS gas VS district heating.
Feedback from users of geothermal heat pumps
Discussion on the points mentioned in this article
Information about thermodynamic heating and heat pumps

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