Geothermal vs. Electric Heat Pump: How to Decide

LESLIE: David in Arkansas is on the line with a geothermal question. What is going on at your money pit?

DAVID: Well, I have leaks, for one. But at any rate, it’s a water furnace unit. It’s about 23 years old and so it’s probably had a good life. I’m just curious, these days, if it’s best to look at replacement with a geothermal or if conventional units are now just as efficient, you know, and which way to go.

TOM: And what kind of fuel do you have right now, David?

DAVID: Our home is all electric.

TOM: So it’s all electric. OK. So, yes, the HVAC systems are far more efficient than they used to be. If you were to go geothermal, you have the investment of having to essentially install the ground line, which basically goes deep into the soil as part of this. And that’s something that’s going to depend greatly on the condition of the soil, whether it can be easily drilled and so on and so forth. The install on geothermal tends to be pretty expensive, so you’re definitely going to have to get some estimates on that and see if it makes sense. If not, I would buy the most efficient electric heat-pump system that you can afford.

And I’d also make sure that you replace both the coil on the A/C side of this, as well. Because the coil has to match, right? You don’t just want to put the unit outside. You have to replace that coil, as well. Because unless they’re properly matched, you do not get the efficiency that you are promised, so to speak.

DAVID: OK.

TOM: And then thirdly, I want you to make sure that you replace the thermostat with one designed for heat pumps. This is a common mistake people make. They put standard clock-setback thermostats on heat pumps. And what happens is if a heat pump runs on the heat pump cycle, the temperature has to move very slowly so it doesn’t trigger the backup system that’s built into all heat pumps, which is electric heat. And if you do that, that gets really expensive to run.

So, replace the heat pump with the most efficient one you can afford, match it with a proper-sized coil and make sure the thermostat is also replaced and is a heat-pump thermostat. And by the way, lots of thermostats today, too, that are Wi-Fi, wireless thermostats. Your phone becomes a remote control.

DAVID: Right, right.