Should Fairfax switch to a heat pump?

In Fairfax, the extra upfront cost technically comes back, just not before the equipment wears out. $3,500 is what Fairfax would pay extra to go electric rather than replace the furnace and AC with the same again, once the $2,000 federal credit is applied. Fairfax's residents would see roughly $224 a year back in running costs, putting the payback around 15.6 years. That's a technicality, not a recommendation, for anyone actually living in Fairfax.

How cold Fairfax actually gets

Degree days tell the story here: Fairfax racks up 3678 heating degree days each year (base 65°F), and summers are hot enough that cooling matters as much as heating, with 1567 cooling degree days on the cooling side. The 99% winter design temperature here — the cold snap equipment must be sized for, not the seasonal average — is 8.1°F, against a record low of 7°F. That puts the seasonal coefficient of performance at 2.89 for the recommended cold-climate unit. Below the 25°F line where a standard machine starts leaning on resistance backup, Fairfax sits firmly in cold-climate territory, so that's the class of unit priced here. Source: NOAA station WASHINGTON DULLES INTERNATION, 9.8 miles from Fairfax — the closest one on record.

Fairfax's running-cost comparison, in dollars

Electricity use for heating alone comes out to about 3,223 kWh a year on the 2000-square-foot reference house; folding in cooling puts the electric bill near $756 a year. That compares with roughly 38 Mcf a year of gas at Fairfax's 16.79 per-Mcf rate — about $980 a year — against a local electricity rate of 16.58¢/kWh. Buy it outright, not incrementally, and payback stretches to 60.3 years; over 15 years the net position sits $139 behind.

If your home heats with electric baseboard instead of gas

Gas isn't universal in Fairfax — many houses run on electric heat already. Swap the comparison to resistance heat instead of gas, and Fairfax's answer improves. The saving here runs about $1,125 a year, which recovers the extra $8,000 spent going electric in roughly 7.1 years.

Where Fairfax ranks in this dataset

Among 3206 cities, Fairfax's winter puts it at rank 1693 for severity, while its size puts it at rank 1523 for population — 1 in both cases being the extreme. That's the middle third for winter severity among the cities covered here.

Next step for 26,340 people in Fairfax

Fairfax, Virginia is home to about 26,340 people, and the figures above are the same ones a local HVAC contractor uses to size and quote a system — this site doesn't guess where a real quote would land, it just tells you whether it's worth asking for one. In Fairfax, nothing is lost by holding off until the current equipment genuinely fails.

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

Where Fairfax's figure comes from

The methodology guide walks through exactly how Fairfax's 2.89 seasonal COP and the rest of this page's numbers get built. Fairfax's 8.1°F design temperature is below the 25°F line, which is why a cold-climate unit is the right call here — see what that changes in the cold-climate unit guide.