Heat pump replacement in Centreville.

A heat pump shows up in the Census as electric heat, and 25 percent of Centreville’s homeowners have it. In a house from the 1980s or 90s that usually means an outdoor unit that cools all summer and heats all winter, and an air handler inside with backup strips for the bitterest hours. Put a new outdoor unit on an old indoor coil and the two are mismatched, often on different refrigerants, so the usual job is both halves replaced and priced as one system.

Centreville also sits across two electric companies. Fairfax County’s utility list puts most of the county on Dominion Energy and portions of Centreville and Clifton on NOVEC. That matters more for a heat pump than for anything else in the house, since a heat pump’s winter heating all comes off the electric bill. Where there’s gas too, the dual fuel guide we wrote calculates the outdoor temperature at which the furnace should take over, and it lands much colder for a NOVEC house than for a Dominion one.

In the other three quarters of Centreville’s houses, the ones on gas, a heat pump would take the air conditioner’s place, and Washington Gas, which serves most of Fairfax County, pays toward that pairing. Its conditions are specific: the heat pump must be replacing a central air conditioner that’s already there, the installer must be on Washington Gas’s participating list, and a heat pump swapped for a heat pump gets nothing. The guide lists today’s amounts.

About one Centreville home in seven is in a condo or apartment building, and where one of those heats with electricity it’s usually a heat pump: a compact air handler behind a hall closet door, the outdoor half up on the roof, out on a balcony or on a pad shared with neighbors. Whatever replaces it has to clear that doorway and fit that spot, and the association may decide what’s allowed outside. Your condo documents say which parts are yours to replace.