Flexibility of Homes

The project carried out and evaluated demand response control of heat pumps in nine villas in southern Sweden, where the owners were informed, but not when the control was done. The tests were carried out in connection with and after Russia's full-scale invasion of Ukraine and the resulting energy crisis, which greatly affected household finances. We see that the households in the project decreased the indoor temperature in February 2023, compared to February 2022, which shows the seriousness.

Large variations were seen in the indoor temperatures of the different households, so large that in some households it was sometimes difficult to discern what impact the project's control had.

We easily managed to switch off the heat pumps from manufacturer B, when we sent a strong enough negative control signal. We could not regulate manufacturer A's heat pumps the first winter, due to missing hardware, and the second winter, the results were variable. We managed to increase the heat output from the heat pumps from manufacturer B.

We showed that we could shift power consumption in four heat pumps by turning them all off at the same time and for two hours. After the switch-off, the heat pumps' power consumption increased a lot, which will be important to deal with in the future.

The initial tests carried out on one of the test exhaust air heat pumps, a more modern variable speed controlled heat pump, showed that the potential to control this type of heat pump was low.

The project has attempted to quantify the flexibility potential per heat pump, in a local electricity grid and at national level. At an individual level, the flexibility potential is sharp, with the highest potential in milder winter conditions, but it depends on the type of heat pump and dimensioning of the heat pump. At even lower temperatures, the potential drops rapidly to zero. If control of the auxiliary heater is allowed, the potential rises at even lower temperatures, in the border country the potential is considered low, but of course it depends on the economic benefit during the hours the compressor and the auxiliary heater are stopped.

At the turn of the year 2023/24, RISE estimated that there were 340,000 heat pumps in hydronic heating systems in Sweden that could be connected over internet. The theoretical flexibility potential of these heat pumps is well under 1 GW, but many older ones are more difficult to connect, so most of them are likely not connected, which is why the above figure is probably too high. If we compare it with the electricity price control that was used in one of the heat pumps in the test, we see that the potential is not used very much, manufacturer B does not regulate this hard at all. Therefore, the project does not set a flexibility figure for Sweden's heat pumps, this needs its own project. It is clear, however, that it increases each year and since we naturally accept and use connected appliances now, many of the newly installed heat pumps will likely be connected.

From the households' descriptions in the interview study, the experience of the experiment with remote-controlled heat pumps was mostly positive. Most of the participants did not notice the effects of the control in terms of changed indoor comfort to any great extent. Once they noticed a difference in indoor comfort, they had a hard time knowing whether it was due to the experiment or some other factor such as weather changes, activities in the home, or the characteristics of the house. This result indicates that there is a certain tolerance for variation in indoor temperature in this type of household, as they were considered normal regardless of the remote control.

When we asked households to reflect on a future service for remote control, it turned out that our participants had low expectations of financial compensation for offering their flexibility through the heat pump. The participants' possible motivation to offer such flexibility was instead about contributing to the energy system and equalizing electricity use, and at the same time reducing price spikes on a collective level. On the other hand, the participants had other reservations and question marks about a future service, especially regarding the service's reliability, security and to what extent the family can influence the system or management so that it fits their needs and everyday life.