Air-source heat pumps work on a novel principle: instead of directly producing the heat that you need to keep warm through the winter, the heat pump will find heat energy in the outside air and bring it into your home, using refrigerant as the medium of heat exchange.
But for it to be effective at doing that, there needs to be enough heat energy available – and as the temperature drops outside, not only does your home take more energy to keep warm, there’s less heat energy that your heat pump can extract from the outside air.
The point at which the extractable heat energy gets too low for a heat pump to adequately heat your home is called the balance point. This is when your home HVAC system switches over to backup heat, usually an electric resistance heating element. But here’s the trick: in many heat pumps, this point is programmed in, which means that it may be set too high.
To understand why this is a bad thing, you have to know a little about heating efficiency. Heater units have a rating called a Coefficient Of Performance (COP), and in electric heating systems (other than heat pumps), that’s a 1: a one-to-one conversion of input energy to output heat. In an air-source heat pump, the COP is a 2-4: you get two to four times as much heat out as you put energy in. So if you switch to a backup electric heat source, you’re also switching to paying two to four times as much for the same amount of heat. (Some air-source heat pumps are backed up by a natural gas furnace, which is a bit trickier to compare with regular heat pump operating costs, since the current cost of natural gas is relatively low.)
If your heat pump can keep your home warm down to, say, 30 degrees F, but your balance point is set to switch over to backup heat at 40 degrees, then anytime the temperature is in the 30- to 40-degree range, you’ll be paying too much for heat (if you use electric backup heating). And during a southwest Illinois cooling season, that temperature range can mean that you’ll rack up some significantly larger heating bills.
To learn more about heat pumps, energy savings and efficiency ratings such as COP and the Heating Seasonal Performance Factor (HSPF, which looks at efficiency over an entire heating season), visit us at Ernst Heating and Cooling. We’re proud to serve homeowners in Hamel, Edwardsville, Troy and other southwest Illinois communities.
Our goal is to help educate our customers in Hamel, Alton, Glen Carbon, Highland, Greenville, and Troy, Illinois and surrounding areas about energy and home comfort issues (specific to HVAC systems). For more information about heat pump balance point and other HVAC topics, download our free Home Comfort Resource guide.
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