The négaWatt and CLER-Réseau associations for energy transition have published a guidance note on heat pumps. According to them, heat pumps have a central role to play in the decarbonization of buildings and the energy transition, provided they are accompanied by a comprehensive renovation strategy.
In a favorable regulatory context, heat pumps (PAC) are developing strongly on the territory to heat housing. But négaWatt and the CLER-Réseau for energy transition fear a dissemination of unsuitable solutions. On January 31, the two organizations unveiled a technical note during a webinar “Role of the heat pump in the renovation strategy” carried out at the end of 2022.
According to this memo, replacing gas or oil-fired boilers with heat pumps in thermal sieves is of interest only if the gesture is accompanied by the performance of an efficient renovation. On this basis, the associations recommend that the government better supervise the installation of heat pumps with additional heating, and direct aid primarily towards efficient renovation.
A second essential heating system
A classic heat pump has its limits. “The most common heat pumps cannot deliver fluids at more than 55°C, explains Olivier Sidler, negaWatt spokesperson. This is both a lot in new buildings and quite a bit in old housing, built before 1975. “ The old dwellings are in fact equipped with radiators requiring temperatures between 80°C and 90°C in very cold weather.
When outside temperatures drop below 5°C or 9°C depending on the region, the heat pump will no longer be able to sufficiently heat poorly insulated dwellings (classified F or G). In the latter and in very cold weather, the interior temperature will not exceed 14°C, specifies the study.
Replacing a boiler with a heat pump in a thermal sieve therefore requires a second heating system. These may be electric convectors, a standby boiler or even a hybrid heat pump (which includes a boiler under the same cover). It can also be a high temperature heat pump that can reach 70 or even 80°C at the condenser outlet. These supplements lead to overconsumption of electricity, amplify the electric peak, require gas to operate, take up a lot of space and lead to a significant additional cost, the study estimates.
The essential renovation in addition to heat pumps
NégaWatt has modeled the effect of replacing gas or fuel oil boilers in half of the F or G classified dwellings in France, ie 1.4 million dwellings. This fleet is a top priority and in line with the objectives of the multi-year energy plan, France’s roadmap. “This corresponds to 280,000 renovations per year by 2028, which is barely half of the objectives of the PPE”says Olivier Sidler.
This sample now emits 7 million tonnes of CO2 per year. Once the substitution has been made, emissions would still amount to 4.5 million tonnes in the event of backup by a boiler, to more than 3 million tonnes with a hybrid heat pump. And for good reason: they still use fossil fuels on the coldest days. Solutions using electric convectors or high temperature heat pumps reduce emissions to just over 1 million tonnes. On the other hand, when the CAP is accompanied by a complete renovation, emissions fall to less than 0.1 million tonnes.
“The use of heat pumps associated with a global and efficient renovation divides by 100 the GHG emissions of gas and oil boilers that exist in class F and G housing”assure Olivier Sidler.
The difference is even more impressive in terms of primary energy. While the fleet taken into account currently consumes 26.3 terawatt hours (TWh) of primary energy, consumption would still be more than 20 TWh in solutions without renovation. Combining a heat pump with comprehensive and efficient renovation would, however, make it possible to reduce consumption to 1 TWh for this housing stock.
Last advantage: associated with a global renovation, heat pumps call for an electrical peak of 0.5 gigawatts (GW). This amounts to nearly 5 GW in the case of an association with electric convectors.