What determines a heat pump's operating cost here

The rate you pay and the efficiency you bought

Operating cost is, at its core, energy used multiplied by what your utility charges for it. South Sound homes sit in different utility territories with different electric rates, so identical systems in Graham and Kent can produce different bills. On the equipment side, HSPF2 summarizes how much heat a unit delivers per unit of electricity across a heating season — a higher number means the machine works your rate harder. Because Western Washington heats for many more hours than it cools, a heating-efficiency advantage compounds across the whole winter, while a cooling-efficiency advantage only matters for a few warm weeks. That's why we weight HSPF2 over SEER2 when helping homeowners here compare models.

Sizing and installation set the real-world number

Ratings assume the system was sized and installed correctly, and that assumption does a lot of work. An oversized heat pump short-cycles — repeated starts and stops that burn energy without delivering steady comfort — while an undersized one leans on backup heat, the least efficient way to warm a home. Refrigerant charge, airflow, and control setup each shave delivered efficiency when they're wrong. Two identical units, one carefully commissioned and one rushed, will show meaningfully different bills for years. This is the piece of operating cost you buy once, at installation, and live with afterward — and it's why the installing contractor matters as much as the brand on the nameplate.

Backup heat: the quiet variable

Most heat pump systems include a backup heat source — electric resistance strips in the air handler, or a gas furnace in a dual-fuel arrangement. Electric strips make heat directly instead of moving it, which is the most expensive mode the system has. When controls are set up well for our climate, backup runs only during rare deep-cold snaps or defrost cycles, and its effect on the bill stays small. When a thermostat is misconfigured, or a homeowner uses big overnight setbacks that force the strips on every morning to recover, backup heat can quietly dominate the bill. If a heat pump's costs seem high, backup behavior is one of the first things worth checking.

The honest comparison with gas

Whether a heat pump costs less to run than a gas furnace depends on the ratio between your electric rate and your gas rate — and that ratio varies by utility and shifts over time. What we can say honestly: moving heat is fundamentally more efficient than making it, our mild marine winters keep heat pumps in their strong operating range most of the season, and a heat pump also replaces your air conditioning, so it's covering two jobs. For a specific home in Tacoma or Olympia, the right move is running the comparison with your actual rates and your actual heating load — which we'll walk through at the kitchen table rather than promising a number in a headline.

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