Should you keep a backup for your heat pump? It depends

When it comes to installing a heat pump, a common decision homeowners have to make is whether they want to keep a backup system heating in their home. If you maintain a backup system, your heat pump will still handle the bulk of your heating needs (and all of your cooling), but you’ll also have a secondary heat source.

You can think of keeping a backup option like a hybrid vehicle – you get much of the comfort, efficiency and environmental benefits of an electric car, as well as the range and convenience of sticking with a part-gas vehicle. It’s a similar consideration for heat pumps: Keeping a backup heating method can offer peace of mind, but it may not be the right choice for everyone.

Traditionally, heat pumps have been installed with backup heat. That’s because until roughly 2015 it was hard to buy a heat pump that worked at all below 30 F. So aside from the parts of the U.S. with tropical climates, in the past you always needed some kind of secondary heating system.

Today, however, keeping a backup heating system isn’t strictly necessary outside of very cold climates. There are plenty of models on the market now that can heat your home flawlessly down to zero Fahrenheit, and can keep producing some heat down to -20 F. You’ll find countless testimonials from people who have installed cold-climate heat pumps, with or without backup, and said the heat pump handles everything on its own, no problem.

There are many different reasons why you might keep a secondary heating method in your home. Depending on where you live in the country, it’s most likely a little bit of all of the factors combined. Here are the main things to take into consideration if you’re on the fence about a backup heating option.

Heat pumps need a lot of electricity to heat your home, whereas a furnace only needs a little, and a wood stove needs none at all. So if you live in an area prone to extended power outages during the winter, it’s probably wise to keep a backup unless you have enough solar batteries to ride out the rapture.

Basic heat pumps stop working when the temperature drops below freezing, so you’ll need a backup if you live in a particularly cold climate. High-performance heat pumps, however, work just fine even in temperatures below 0 Fahrenheit—but they do lose some energy efficiency at those temperatures, which means it can be more economical to heat your home with gas once the mercury crosses below a certain threshold.

Dealing with humidity

Certain climates, where it’s both really humid for much of the year (including the spring and fall), but also regularly falls below freezing during the winter, can pose a design challenge. One way to address this is by installing a heat pump that’s sized for the cooling load, then making up the excess heating needs with a backup system. (In fact the ACCA Manual S rules recommend this, though most working professionals will tell you it’s not the right approach for dry climates or truly cold climates.)

Creaky infrastructure

Old homes might have less than stellar ductwork, poor insulation, and crowded electrical panels. In cold climates especially, switching exclusively to a heat pump could be a challenge because of the sorry state of your home’s infrastructure. You could fix the infrastructure, which is often the most foolproof option. But if that’s not in the budget (and it often won’t be), then a backup system makes the most sense.

The type of backup heat you choose will depend on what type of climate you live in, the physical state of your home and how much you can afford to spend for your heat pump installation.

Electric resistance heat is essentially like a gigantic blow dryer or toaster oven you attach to your home’s ductwork. It’s expensive to run, but super-cheap to install. It’s best used as a true backup option: During those few days per winter (if that!) when it’s dramatically and unusually cold, and temperatures surpass what your heat pump and ductwork are scoped to handle on their own. You can also get a heat kit in case something about your heat pump malfunctions. No ductwork? Electric baseboard radiators could be a backup option.

These are typically a lot less expensive to run than electric heat strips—and often less expensive than the heat pump itself, at least once the outdoor temperature drops below a certain point, and depending on the relative costs of utilities.

• If you’re in a climate where it regularly drops below 35 F, but you don’t want to rely entirely on a heat pump for one reason or another—whether it’s cost, security, or your home’s infrastructure might not support it—then this option could make sense.

• You can install a new heat pump that works with an existing furnace. With oil, that’s probably the way to go. With gas, generally it’s more energy efficient and sometimes less expensive to just get a new matching heat pump and furnace. 

This is a popular one for people who get ductless mini-splits. You just keep your old gas or oil boiler and radiator system in place. There are ways to set up integrated controllers so that the boiler automatically fires up once the outdoor temperature drops below a certain point.

This one is pretty self-explanatory: You have the most traditional heating system of all that you can fire up in a pinch, whether that’s a power outage or an extreme cold snap. You don’t have to worry about depending on electricity at all.

Heat pumps are heavily incentivized in some states. Massachusetts, for example, offers a $10,000 rebate for installing a whole-house heat pump—but under the current rules, you must remove or disconnect your existing system to qualify for that full rebate. You can still claim a smaller rebate if you keep a backup (or install a new one). It’s something to watch out for in the fine print of any rebate / incentive programs in your area.