Will a heat pump pay off in Watertown, WI?

Watertown is a place where a heat pump genuinely costs more to operate than the alternative. Against a like-for-like gas furnace and AC swap, going electric costs $3,500 more up front here (already netting out a $2,000 tax credit). Unfortunately the electric bill outweighs the gas bill it replaces by about $468 a year here, so the extra spend stays unrecovered. There's no spin on that: Watertown's numbers say wait.

The climate behind Watertown's payback figure

6257 heating degree days pile up here every year, so Watertown has a cold winter that leans hard on heating equipment; the cooling side runs to 454 cooling degree days, where summers add a moderate cooling load. The 99% winter design temperature here — the cold snap equipment must be sized for, not the seasonal average — is -9°F, against a record low of -11.6°F. That puts the seasonal coefficient of performance at 2.48 for the recommended cold-climate unit. Watertown needs the cold-climate class of unit: past a 25°F design temperature a standard heat pump falls back on resistance backup often enough to eat the savings. Source: NOAA station DODGE COUNTY AIRPORT, 16.4 miles from Watertown — the closest one on record.

Watertown's running-cost comparison, in dollars

Electricity use for heating alone comes out to about 6,389 kWh a year on the 2000-square-foot reference house; folding in cooling puts the electric bill near $1,279 a year. Watertown's gas rate of 10.74 per Mcf, applied to the 65 Mcf a year the furnace burns, puts its running cost near $811 a year, against 18.87¢ per kWh for electricity. Looked at as a full purchase rather than an incremental one, payback here is longer than the 15-year equipment life, leaving the 15-year total $10,515 behind.

The other scenario: no gas furnace to begin with

Plenty of homes in Watertown heat with electricity alone, no gas line involved. Against electric-resistance heat — baseboard or an electric furnace, both 100% efficient but still just resistance — the case for switching gets stronger here. Switching saves about $1,822 a year here — a heat pump moving heat rather than generating it needs far less electricity than resistance coils — so the extra $8,000 spent up front comes back in about 4.4 years.

Where Watertown ranks in this dataset

Among 3206 cities, Watertown's winter puts it at rank 129 for severity, while its size puts it at rank 1743 for population — 1 in both cases being the extreme. That's the coldest third of the dataset, where climate does most of the work behind this figure.

Deciding what's next in Watertown, WI

About 22,617 people live in Watertown, Wisconsin, and every number on this page is what a contractor would actually work from when quoting a system here — the point isn't to replace that quote, it's to tell you whether to bother asking for one. Here, there's no cost penalty to waiting until your current furnace or AC actually needs replacing.

Ask a local HVAC contractor for a quote before committing either way.

Where Watertown's figure comes from

The methodology guide walks through exactly how Watertown's 2.48 seasonal COP and the rest of this page's numbers get built. Watertown's -9°F design temperature falls on the cold side of the 25°F cutoff the cold-climate unit guide walks through.