We protect computers by plugging them into electrical surge protectors. Contemporary heat pumps are essentially computers hooked up to compressors and fan motors. Why don’t we protect them from surges also?
In 2013, when Diana Lane and her husband Yonatan Malin bought their century-old home near downtown Boulder, Colorado, it came equipped with baseboard heat, warmed by a gas-fired boiler. A few years ago, Diana and Yonatan, seeking to minimize their climate impact, installed a heat pump, and eventually shut down their boiler and gas connection a few years later.
The heat pump worked just fine, until late in the winter of 2025, when it suddenly conked out. Service technicians found that both the control board and a fan had failed, likely due to a power surge. What’s a power surge? It’s a momentary fluctuation in an electrical system that sends a burst of higher than standard voltage coursing through the wiring. Usually, our equipment survives these surges, but sometimes they’re so powerful, they damage microprocessors and copper windings.
Since heat pumps are essentially small computers managing compressors and fans, you’d think that the contractors who install them would recommend adding in surge protectors, just as computer manufacturers recommend plugging their products into surge-protecting power strips. Surprisingly, few do, even though fixing a surge-damaged heat pump can cost more than a new computer.
When it came to fix their heat pump, Diana and Yonatan got lucky. The manufacturer deemed that their control board and fan failures were covered under warranty. Not all manufacturers do that. They still had to pay for the labor to replace those components, and that wasn’t trivial. Their heat pump was manufactured by a Japanese company, and no English language service manuals were available. Instead, the local service technicians had to call up the factory techs in Japan for instructions, sometimes having to wait on hold until the factory people were available. “One time they had to wait on hold for two hours,” Diana told me. Fortunately, the local service company decided not to charge Diana and Yonatan the full cost of the repair.
Also, a new control panel and fan weren’t immediately available. Instead, it took two weeks for them to come in. Again, with good fortune, during that time the weather was moderate, and Diana and Yonatan were able to heat their home with plug-in electric heaters.
If you’re installing a heat pump, or an air conditioner, please do yourself a favor. You can avoid the expense and trouble Diana and Yonatan went through by installing a surge protector. These devices contain a variety of electronic components that stop or shunt off high electric voltage currents before they reach sensitive electric equipment. Usually, they cost much less than a single surge-caused repair and are easily installed. Diana told me she was planning on getting one.
Power surges explained
Power surges are often so brief, usually just a few thousandths of a second, that they are often undetectable by ordinary volt meters. During that ephemeral instant in time, the voltage may rise as high as hundreds of times the standard voltage that nearly all household appliances operate at. Most electrical equipment is designed to handle minor power surges, but occasionally, one comes along that’s so intense it’s damaging. Alternatively, repeated minor surges can cause enough cumulative damage over time that equipment fails.
Surges can be divided into two categories: Those that originate outside the home, and those that are internal. Of the external sources, the most destructive type is undoubtedly lightning strikes. A flash of lightning can exhibit voltage ranging from tens of millions of volts to a billion volts. To put that in perspective, a typical US home is mostly wired for 120 volts.
Lightning doesn’t have to directly hit your home to be destructive. It can travel through metal water pipes, cable TV cables, internet cables, and yes, electric wires. No one has ever established a safe distance from a lightning strike at which there’s no risk of electrical equipment damage, but instances of damage resulting from strikes one mile away have been reported.
Another common external source is utility equipment switching. Utilities need to constantly switch circuits on and off, or between different generators and distribution networks. Sometimes that switching produces surges, and sometimes those surges are powerful enough to cause damage.
As for internal surges, a main cause is static electric discharges, usually from people touching equipment under extremely dry conditions. You might not even need to see a spark to produce enough voltage to damage equipment. Another cause is large equipment, like a refrigerator, switching on and off. Lastly, faulty wiring and overloaded circuits can lead to surges.
How surge protectors work
Let’s be clear. If lightning directly strikes your house, a surge protector is not going to be able to protect your heat pump from damage, although your homeowners’ insurance might cover your losses. For less intense surges, protectors work in multiple ways, but most surge protectors contain electronic devices called varistors. They are electric resistors whose resistance varies depending on the voltage they’re exposed to. When they see voltage close to what’s standard, they exhibit high resistance, and virtually no electricity flows through them. When exposed to higher voltage their resistance drops, diverting that high-voltage electricity to ground.
How to choose a surge protector
Surge protectors vary widely in both quality and additional features. Here are some of the most important characteristics to consider when choosing one.
Cost. Surge protectors suitable for heat pump duty may range in cost from $50-$400. Units on the higher end of this range are designed for larger equipment and contain more bells and whistles, but you can find units that are reasonably good for ordinary residential equipment for about $70-$100. Expect to pay an additional $100-$150 for installation.
Diagnostic indicator. Every time the varistors in surge protectors are exposed to high voltage they lose a little bit of their effectiveness. Over time they wear out, and the overall surge protector needs to be replaced. Depending on the quality of the surge protector, and the quantity and intensity of surges, a protector might last from 3-5 years. How do you know when it’s time to replace one? Get a protector that features an LED light that indicates when it’s no longer fully functional.
Warranty. Surge protectors typically feature warranties ranging from 1-10 years. Most only cover manufacturing defects, not ordinary wear and tear. Also, some manufacturers offer reimbursement for equipment damage the protector failed to prevent, sometimes as much as $25,000.
Certification. Look for protectors that are certified to UL Standard 1449, which addresses the safety and performance of surge protective devices. It ensures that any certified model has been tested and is capable of its rated performance. There are many low-cost protectors on the market that appear to be knockoffs of popular units, but they aren’t UL certified. I don’t know how these low-cost units compare in quality to the certified units they’re modeled on, but if it were my house, I’d insist on getting an actual UL certified unit.
The go-to protector for heat pumps
I found that one protector was most frequently recommended by contractors: The Intermatic AG3000. For an example of such a recommendation, and some insight into competing products, I suggest this review titled titled 6 Best AC surge protectors for HVAC safety and performance.
The AG3000 is available for about $70 from online distributors like this one, and the manufacturer claims that it’s easy to install, typically taking about ten minutes. It works with both 120 volt and 240 volt equipment and features an LED status-indicating light.
Intermatic offers a 3-year warranty on surge-related damages to compressors, and other electronic components, up to $7,500. This warranty may not apply to any repairs covered by a home insurance policy. It comes in a weatherproof box, so it can be installed either indoors or outdoors.
How to install a surge protector
To install a surge protector, mount it on a heat pump’s disconnect box, and connect the wires according to the manufacturer’s instructions. What if that box is outside on the side of the house? Usually, that’s not a problem, as many surge protectors come in weatherproof boxes.
Can this be a do-it-yourself project? Maybe, if you’re comfortable with electrical work.
Often, the AG3000, and several competing products, may well be capable of protecting your entire house. In such cases, some electricians advocate for installing the protector on the main electric panel in order to protect all the electric equipment in the house.
The problem with that approach is that it would only protect your equipment from surges originating outside of the house, but remember from above, many surges are produced internally. While internal surges may not be as intense as those coming from lightning, they’re often more frequent. To protect your heat pump from these surges, as well as external surges, you’ve got to install the protector close to the heat pump, preferably at the disconnect switch.
If your house is in an area that’s especially vulnerable to lightning-related surges, you can install two protectors: One at the main panel and one at your heat pump. That would protect everything in your house from external surges, and your heat pump from all surges regardless of where they originate.
Final thoughts
Incorporating a surge protector into a heat pump is a lot like getting an insurance policy. You hope you never need it and maybe you won’t. But adding about a percentage point to the cost of a new heat pump installation to guard against thousands of dollars of losses and plenty of inconvenience and aggravation, sounds like a good deal to me. What’s more, it’s easy to do. So, take Nike’s advice, and “just do it.”
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Lastly, check out these other recent ETR posts on heat pumps and air conditioners: