Answers
Do I need backup heat with a heat pump in Bellingham?
Usually yes, and often you already own it. How backup heat interacts with the 19°F design temperature, the PSE lockout requirement, and keeping a few baseboards on the wall.
The short answer
Usually yes, and often you already have it. Barron Heating’s own FAQ recommends keeping a backup source ready for when temperatures drop too low, whether gas, propane or electric. In Bellingham the practical answer is to keep some existing heat in place for the handful of nights near our 19°F design temperature.
What backup is actually for
Backup covers two situations, and they are different. One is a cold snap below your system’s balance point, where the heat pump keeps running and something adds the missing capacity. The other is a hard failure or a defrost problem, where you need heat while you wait for a part. Sizing generously helps with the first and does nothing for the second.
Keep some of your baseboard
When we convert a baseboard house to ductless, we often leave a few original heaters in bedrooms and bathrooms on their own thermostats. They cost nothing to keep, they are already wired, and they give you a room-level fallback that no ductless layout provides. The bathroom in particular benefits, since a small tiled room on the north side is the one place a distant indoor head never quite satisfies.
The PSE lockout requirement is not a contradiction
PSE requires electric resistance backup to be locked out via an outdoor sensor, with a recommended lockout at or below 35°F, and the compressor lockout disabled or set at 0°F or below. That is not a ban on having backup. It is a rule that the strip heat cannot pick up the load at 40°F where the heat pump is far cheaper to run, which is exactly the misconfiguration that produces a shocking January bill.
Foothill and rural homes plan differently
Glacier designs to 13°F and Blaine to 17°F, so the cold-snap case is more common there than in town. Those homes usually already have a woodstove, propane furnace or oil unit, which makes an excellent backup and one reason we rarely recommend ripping the old system out on day one. In the foothills we also plan for the outdoor unit to sit above expected snow depth.
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