Using air source heat pumps for space heating delivers comfortable, stable, and energy-efficient heating results, along with high environmental friendliness and a long service life. air source heat pump.Therefore, ASHP heating has become the main force in the "coal-to-electricity" transformation projects. With continuous technological advancements, ASHP heating / air source heat pump has gradually entered thousands of households. For many users who have never used ASHP heating / air source heat pump, the primary concerns are power consumption-related issues, such as daily electricity usage, how to handle tiered electricity pricing, and whether household electricity supply can withstand the load.
Comparison Between ASHP Heating and Electric Resistance Heating
ASHP heating / air source heat pump use electricity as the driving power and can provide cooling, heating, and domestic hot water. However, the ASHP heating / air source heat pump main unit only requires a small amount of electrical energy to drive the compressor, which compresses and converts the low-temperature heat absorbed from the air into high-temperature heat needed for heating.
Calculation Example: Heat Required to Heat 1 Ton of Water from 15℃ to 45℃
What is the heat Q required? How much electricity is needed for electric resistance heating versus ASHP /air source heat pump heating?
Q = 1×1000L×(45℃-15℃) = 30,000 kcal = 34.89 kWh
- Electric resistance heating: Thermal efficiency = 90%, Power consumption = 34.89 / 0.9 ≈ 38.77 kWh
- ASHP heating: Coefficient of Performance (COP) = 3.26 at 5℃, Power consumption = 34.89 / 3.26 ≈ 10.70 kWh
- ASHP heating: COP = 2.37 at -5℃, Power consumption = 34.89 / 2.37 ≈ 14.72 kWh
It is evident that the power consumption of ASHP heating is only 27.60%-37.97% of that of direct electric resistance heating. Using ASHPs / air source heat pump for heating can significantly reduce electricity costs.
Key Reasons for High Power Consumption of ASHPs
1. Incorrect ASHP Unit Sizing
ASHPs are available in various models, including normal-temperature type and low-temperature type. Their thermal efficiency varies under different environmental conditions:
- Using a normal-temperature ASHP for heating in low-temperature areas will lower the COP, and the unit may even shut down due to weak defrosting capacity, resulting in high power consumption.
- Using a low-temperature ASHP heating / air source heat pump in high-temperature areas achieves high COP but incurs higher initial investment costs.
2. Extremely Low Outdoor Temperature
Low-temperature ASHPs can operate in cold winter regions, with a minimum operating temperature of -25℃, which meets the winter temperature conditions in most parts of China. However, if the ambient temperature drops below -25℃ in some areas, the COP of ASHPs will decrease, leading to increased power consumption (lower COP = higher power consumption).
3. Malfunctioning Temperature Sensor
ASHPs rely on temperature sensors to detect water temperature, thereby controlling the operating frequency of the main unit for energy savings. If the temperature sensor malfunctions or is improperly installed, it may detect an inlet water temperature lower than the actual temperature. This causes the hot water to be heated continuously until the high-temperature protection is triggered, increasing power consumption and resulting in excessively high indoor temperatures.
4. Poor Building Insulation
The stability of indoor temperature is related to building insulation. Poor insulation leads to rapid heat loss from the indoor space, forcing the ASHP unit to continuously supplement heat, resulting in high long-term power consumption. In contrast, good insulation allows the ASHP unit to operate at low frequency for longer periods after reaching the set temperature, reducing electricity usage.
5. Improper Underfloor Heating (UFH) Design
Traditional gas boiler heating, limited by thermal efficiency, typically uses a UFH supply water temperature of 50℃-60℃. However, UFH is more energy-efficient at a supply water temperature of 34℃-45℃. Gas boilers, however, do not achieve optimal energy efficiency at 35℃-45℃, so their UFH systems require coil spacing of 15 cm or 20 cm with coil diameters of 1.6 cm or 2.0 cm to meet the 50℃-60℃ supply water requirement. For ASHPs / air source heat pump (supplying water at 35℃-45℃), smaller-diameter UFH coils are sufficient. Using overly large-diameter coils in ASHP systems will increase power consumption.
6. Inadequate Maintenance
ASHPs /whole home heat pump are affected by water quality in the pipelines and environmental factors:
- In areas with poor water quality, the heat exchanger of the ASHP unit is prone to severe scaling, increasing thermal resistance and power consumption.
- In areas with high environmental pollution, dust, oil fumes, and lint in the air easily adhere to the fins of the ASHPs /whole home heat pump main unit, reducing heat absorption capacity and increasing power consumption.
Regular maintenance of ASHPs /whole home heat pump is crucial for energy savings and extending the unit's service life.
7. Usage Habits
The power consumption of ASHPs /whole home heat pump is also related to user habits. The comfortable indoor temperature range is 18℃-22℃:
- Lower indoor temperature settings result in lower energy consumption. Each 1℃ increase in indoor temperature raises energy consumption by 5%-10%.
- Lower ASHPs /whole home heat pump supply water temperature also reduces heating costs. Excessively high indoor temperatures not only increase power consumption but also reduce comfort, causing stuffiness.
Conclusion
Air source heat pumps / ASHPs /whole home heat pump adopt inverter technology and enhanced vapor injection (EVI) technology, producing 3-4 times more heat energy per kilowatt-hour of electricity consumed, resulting in high energy efficiency and low power consumption. The main reasons for high power consumption of ASHPs are incorrect unit sizing, extremely low outdoor temperatures, improper UFH design, inadequate maintenance, and poor usage habits. By addressing these factors during the design and use of ASHP heating systems, electricity consumption can be significantly reduced.
