Does air-source heat pump heating uses too much electricity? Check the switch mode and water temperature settings.
As living standards improve, more and more users use heating in winter, and people are paying increasing attention to the energy consumption of heating equipment. With the continuous advancement of the northern “coal-to-electricity” project, air-source heat pumps, as new, clean, environmentally friendly, and energy-efficient equipment, have risen rapidly and become widely used in central heating. Thanks to their dual functionality of air conditioning and underfloor heating, and their excellent performance in comfort, stability, energy saving, environmental protection, long service life, and wide application range, many individual households also use air-source heat pump systems.
Air-source heat pumps are designed to be energy-efficient; under the same conditions of area, usage time, and temperature environment, the cost of heating with air-source heat pumps is lower than that of electric heaters and gas boilers—usually only 1/3 of the cost of electric heaters and 1/2 of the cost of gas boilers.
However, many people fail to achieve the best energy-saving results even with properly designed and installed air-source heat pump systems, and end up with high electricity bills, earning the reputation of “energy hogs.” What causes air-source heat pump heating to consume so much electricity?
Frequent on/off switching
Some users (especially the elderly) think that using heating is like switching a light: turn it on when you get home and off when you go out, which they believe will save electricity. In fact, the opposite is true—it doesn’t save electricity; it consumes more.
In winter, air-source heat pumps can use fan coils or underfloor heating for heating. If using fan coils, frequent on/off switching will result in slightly lower power consumption, since fan coils blow hot air quickly. However, for heating comfort, most people use underfloor heating. The working principle of underfloor heating is that circulating water flows and dissipates heat on the floor, heating the floor, and then the heat rises into the room. Therefore, most of the heat heats the concrete between the underfloor heating pipes and stores some heat, which is why underfloor heating has good heat storage and a delayed start-up effect. After turning on underfloor heating, it takes a long time for the room to reach the set temperature—generally 5-6 hours, and even more than a day for large houses. Conversely, when underfloor heating is turned off, the indoor heat does not dissipate quickly; it takes several hours to cool down completely. If we switch underfloor heating on and off frequently, we not only fail to save energy but also spend more time heating the concrete, increasing operating costs during heating, and the room temperature will not be constant, reducing comfort.
For controlling the on/off of underfloor heating, the correct approach is: turn off heating in rooms that are not commonly used, and keep heating running normally in frequently used rooms. If you go out for a short time (1-2 hours), set the thermostat to a lower temperature, and increase it when you return home—this not only maintains the room temperature but also saves energy. If you go out for a long time (more than 3 days), you can turn off the underfloor heating system, but do not cut off the power; in low-temperature weather, the air-source heat pump can activate its self-start protection function to prevent water in the pipes from freezing and cracking the pipes or other equipment components. If the house is unoccupied for a long time and the winter ambient temperature is below 0°C, you need to drain the water from the pipes. Of course, in southern regions with higher winter temperatures, you can add antifreeze to the pipes to prevent freezing.
Setting the water temperature too high
To quickly increase the indoor temperature, many users think that setting the heating supply water temperature higher will help, and some even want to set it above 60°C. However, underfloor heating is a low-temperature water supply and heat dissipation system; setting the temperature too high not only fails to heat up quickly but also reduces the service life of the underfloor heating pipes and increases deposits (scale, biofilm, etc.) inside them. Moreover, for every 1°C increase in the outlet water temperature of the air-source heat pump, the heating capacity decreases by 1%-2%. Under the same conditions, the higher the outlet water temperature, the lower the thermal efficiency, and of course, the higher the power consumption of the air-source heat pump for heating. (When the indoor temperature exceeds 20°C, each 1°C increase in indoor temperature will increase the energy consumption of gas boiler heating by 5%-10%.)
Air-source heat pumps can produce hot water at 35°C-60°C. Once the room temperature is constant, setting the heating supply water temperature below 45°C and controlling the system flow rate and velocity are sufficient to meet the heat supply of the indoor underfloor heating, and the energy consumption of the air-source heat pump will be significantly reduced. At the same time, the start-up frequency of the air-source heat pump will also decrease, further lowering energy consumption.
Summary
There are many factors affecting the energy consumption of heating equipment. Under the conditions of a properly designed and installed air-source heat pump system, if the energy consumption of air-source heat pump heating is very high, you need to check whether there is frequent on/off switching of the heating and whether the water supply temperature is set too high. Of course, during use, you should also pay attention to the thermal insulation of the house—many people are used to opening windows for ventilation, which causes a lot of heat loss, thereby increasing the energy consumption of the air-source heat pump for heating.
