Replace a Heat Pump With a Gas Furnace to Save Money
LESLIE: Okay. Jason from Delaware needs to know the difference between a heat pump and a heater. Jason, how can we help?
JASON: That’s basically the question. The house is about 3,500 square feet and, of course, we have the heat pump for upstairs and regular gas heater for downstairs. And my electric bill is topping out at over $300 a month …
JASON: … and I want to know if there’s a … that heat pump. Should I have it on? What’s it exactly do?
TOM: Yeah, good question. Why, may I ask, Jason, do you have a heat pump on one zone and a gas furnace on the other zone?
JASON: That’s how the house was built.
TOM: Huh. So it’s just kind of one of those things that you inherited. You don’t exactly know why.
TOM: Okay. Well, the problem is that you should have two gas furnaces; not one heat pump and one furnace; especially in Delaware where it gets super cold out. The heat pump is much like an air conditioner that runs in a reverse refrigeration cycle. In fact, the compressor on the outside of your house probably gives you air conditioning on that zone as well. And the only difference between the compressor that runs a heat pump and the compressor that runs an air conditioning system is a part called a reversing valve. And the reversing valve simply does just that; it reverses the flow of refrigerant. So think of a window air conditioner. You know it blows hot air out and cold air in. Well, if you could turn it upside down and shove it back in the window, you’d sort of have a heat pump. That’s basically what a heat pump is.
But the downside of a heat pump, Leslie, as we’ve talked before, is that it just doesn’t do a good job of keeping up with the drop in temperature in a really severe, cold area like Delaware.
LESLIE: Well, and it’s really expensive.
TOM: Yeah, exactly. What’ll happen is if you set your heat at, say, 72 and it gets cold outside and the temperature inside the house falls to 71 or 70, the heat pump will come on and it will use that refrigeration cycle to add heat to your home. However, if the temperature drops below 70 – more than 2 degrees between what you set it at and what it actually is in the house – guess what that heat pump has for a helper? It has a backup electric resistance furnace. And basically, that is the most expensive way to heat anything; with resistant heat. So those coils kick on, the electric meter starts spinning and the people at the electric company are having a big party at your expense. (chuckling) Exactly.
So I would recommend that you replace that heat pump, if possible, with a gas furnace. Now, the super efficient ones …
LESLIE: Is that an easy improvement? How do you know if you’re capable of making that adjustment?
TOM: Here’s what you need to do. You need to A – get the gas line up to where the heat pump is; so, easiest way you can. And secondly, you need to get that gas furnace vented. Now, that can actually be easier than you think. You don’t need a regular chimney for that because the high efficiency gas furnaces go out through a plastic vent pipe. So, it actually may not be that complicated to get that thing vented. But I think that that is going to be your improvement, here, and the only one I can really suggest.
In the meanwhile, you might want to think about a clock setback thermostat for the heat pump. But the thing is, Jason, if you get a clock setback thermostat for the heat pump, you need to make sure that the clock setback thermostat is designed specifically for a heat pump. It’s different than the regular setback thermostat that you might use downstairs on a gas furnace. Because what the heat pump clock setback does is it moves the heat ever so slowly up and down. If you bounce the thermostat from one temperature to another, the electric resistance heat’s going to go on all the time. But if you inch it very slowly so you don’t exceed that two degree differential, then you’ll be okay.
So those are really your options. Clock setback thermostat designed for the heat pump or just replace it with a gas furnace.
TOM: Okay, Jason? Thanks so much for calling us at 1-888-MONEY-PIT.