Central Region

Things I learned about heat pumps: a homeowner's perspective

October 2022

We built our house in 2020-21, right in the middle of the pandemic. We were downsizing as our son prepared to graduate from high school, and we were anxious to keep expenses low over the long term as we age. As a CERTs team member, I wanted to share some of what we learned from making heat pumps our primary heat source in a new build. 

The house is a little over 900 square feet, slab on grade, 2x6 stick-built construction, one main floor with a small loft. It has southeast-facing windows for passive heat in the winter, and blown-in cellulose insulation. (Yes, we know spray-foam is better, but in that particular moment, in our geographic area, the cost difference was just too big for our budget.)

Our home is located in north-central Minnesota.

Our area does not have natural gas service, so for our heating fuel, we had to choose between propane and all-electric. We opted for all-electric, with the idea of adding solar as soon as feasible.

Since it’s important to keep the slab from freezing, the home design included in-floor heat with a small electric boiler. In the winter, we have the floor heat set to turn on briefly once a day to maintain the slab temperature - and give us nice warm feet in the morning.

However, since I’m kind of an energy nerd (and since we wanted to keep our heating and cooling costs low), I was keen on the idea of doing most of our heating with a cold climate air source heat pump.

Because we were not planning on ductwork, we opted for a mini-split configuration. Our general contractor had worked on several projects involving mini-splits before, so he had an HVAC contractor in mind. We deferred to his judgment on that, just specifying that we were specifically looking for an “EnergyStar-certified cold-climate air source heat pump.”

Fortunately, that is what they installed.

It turned out to be a Bryant system with a heating season performance factor (HSPF) of 10.3. For cold-climate models, the HSPF should be greater than 10 (for ductless systems like ours) or 9 (for ducted systems).

There is one outdoor unit that is connected to three indoor heads: a small head in each bedroom and a larger head in the loft to heat and cool the rest of the house. With this being new construction, the line sets connecting the outdoor unit with each indoor head are located inside the walls, not on the exterior of the house (as you would see when adding mini-splits to an existing house).

One nice aspect of ductless heat pump systems: zoned heating and cooling! In other words, I can keep my office space a little warmer than my spouse keeps his, which makes both of us happy.

Things we didn’t know to start with, but we do now:

Before you get a new system installed, think about what’s important to you in your heating system. 

If you want your heat pump to be integrated into a single system with your secondary heat source (furnace, etc.), with one single thermostat controlling everything, you’re probably going to want a ducted system. If you like zoned heat/cooling, or if you don’t want to deal with getting ductwork installed, then a mini-split is probably a better option.

You know how with a forced air furnace system, you are supposed to change your furnace filter monthly, and get a tune-up each year? It turns out that our mini-split heat pump has similar requirements. 

The indoor air filter should be cleaned monthly (it’s not hard to do - just remove the filter, rinse the dust off at the sink, and dry it before putting it back). The outdoor coil should be cleaned from the outside every six months (also not difficult - just a quick spray with a garden hose) and cleaned by an HVAC tech annually.

So the amount of maintenance is comparable to that recommended for any other heating system.

If you get a heat pump installed, ask your contractor to walk through recommended maintenance with you. We didn’t think to do that, but it would have been nice.

As temperatures outside drop, heat pumps don’t heat the indoor air quite as fast, so if you were in the habit of setting your thermostat waaaaaaaaay back at night or when you leave the house, you might want to set it back a little less - or not at all.

In our previous home, which had a natural gas forced air system, we turned the thermostat down 15 degrees at night (we like it cold for sleeping). With the new system, heat pumps run more efficiently when maintaining a constant temperature than when dealing with dramatic changes in thermostat settings. So we set the thermostat back a few degrees at night and use the zoned capabilities to keep just the bedroom at a cooler temperature overall.

This way, we can rely more on the (more efficient) heat pump and less on the (less efficient) floor heat.

Learn more about thermostat setbacks.

In the winter, the outdoor unit will occasionally stop heating for a short time and make some weird noises.

Don’t be alarmed. It’s not malfunctioning. It’s not possessed. It’s just defrosting.

The outdoor unit is mounted on a platform a bit off the ground.

If it’s a really snowy winter, like we had last year, snow can still pile up around it.

When you go out to shovel your walk after it snows, make a practice of checking to be sure your heat pump is clear.

Overall, there have been just a few small hiccups as we learned the best way to use our new system, and it has worked great!

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