Furnace replacement in Paeonian Springs.

Propane heats nearly half the owner homes in ZIP 20129, electricity about 35 percent and oil nearly one in five, while natural gas registers at zero. So a furnace replacement here is mostly a propane furnace. If your house burns oil, we don’t work on oil burners; a propane furnace or a heat pump is what we would price instead. Either way the answer starts as a range, $4,285 to $14,040, and the estimator quiz narrows it to your house.

The median owner home here dates to 1997, so the furnace is likely close to three decades old, and about one in four owner homes predate 1980. Furnaces from that era mostly exhaust through a flue or chimney. New high-efficiency furnaces send their exhaust out through plastic pipe, so the old chimney may end up unused. Loudoun County Fire and Rescue says to have heating equipment and chimneys cleaned and inspected every year by a qualified professional, so ask what happens to yours.

Loudoun County wants a permit on a gas furnace swap. Plans only come into it when the unit’s BTUs or its location change; a like-for-like replacement has been exempt from them since October 2025. A furnace picked too large, or moved, steps outside that. Ask the installer to put the new unit’s BTU rating beside the old one on the estimate and to say who files the permit.

Where the vent pipes leave the house matters in snow. A trained spotter measured 13.0 inches a mile southeast of town on February 21, 2015, and Loudoun’s building code uses a ground snow load of 30 psf. A side-wall intake and exhaust has to sit above where snow piles up, and the Purcellville station counts more than a hundred freezing nights a year to test whatever you choose.