Furnace replacement in Haymarket.

The Town of Haymarket’s own utility list names Columbia Gas of Virginia as the gas company, not Washington Gas, and gas heats about six in ten owner homes inside the town limits. That changes the efficiency question. Columbia Gas pays its residential customers a rebate on a new natural gas furnace in three steps, at 90, 95 and 97 percent AFUE (the efficiency rating on the label), larger at each step. The catch: natural gas has to be the home’s main heat, the furnace has to replace one in an existing home, and Columbia Gas says its rebate quantities are limited and approved first come, first served.

Most houses in town went up in the 1980s and 90s, around a 1995 median, so the furnace in one today is rarely the first. Often the air conditioner has been replaced along the way too, after a leak or a compressor that quit some July. When the cooling side is the younger half and still running well, the furnace alone is the job. Read the outdoor unit’s sticker for its year and refrigerant before deciding.

Dominion Valley and Piedmont tell a different story. Nearly half of all homes in 20169 were built between 2000 and 2009, so plenty of county-side furnaces are the builder’s, near twenty years old, with an air conditioner outside just as old. When both are originals, get the pair priced too, $8,898 to $23,000 installed. About three homes in ten in the ZIP are from 2010 or later; a furnace that young is usually worth fixing, and the $99 diagnostic visit prices the repair first. For any of them, the HVAC replacement cost estimator gives your house its own number.

Propane heats about one owner home in fifteen across 20169 and about one in eight in Bull Run Mountain Estates, where the median house dates from 1978. A propane furnace sits in the same price range as a natural gas one and is set up for propane before it’s lit. Columbia Gas’s rebate doesn’t reach a propane house, since it’s written for homes heated mainly by natural gas.