Here is the thing that tells you more about heating in Reston than anything else we could say: we almost never see a boiler here. In Alexandria and McLean we work on them regularly. In Reston the heating equipment is a heat pump or a gas furnace, and across a large share of the clusters and condos it is a heat pump.
That matters in December, because a heat pump behaves nothing like a furnace and the difference sends a lot of people to Google convinced something is broken when it is not.
Why Reston is heat pump country
Robert E. Simon bought the land in 1961 and the community went up over the following decades as clusters, townhouses, mid-rises and single family homes designed as a whole rather than a subdivision at a time. A lot of that housing was built all-electric, and all-electric in this climate means a heat pump. Fifty years later the equipment has been replaced two or three times, but the fuel choice usually has not: if there was no gas line to the cluster in 1972, there is rarely one now.
So our Reston winter calls come from three groups. All-electric clusters and condos in 20191 and 20190 running heat pumps with electric backup. Single family homes in 20194 and the later neighborhoods running gas furnaces. And a growing number of both running ductless heads in additions, sunrooms and converted garages.
The four things that are normal, and cost you nothing
Every winter we get paid to tell Reston homeowners their heat pump is fine. We would rather you knew for free.
The air from the vents feels cool. A gas furnace delivers air around 125 degrees. A heat pump delivers it in the 90s to about 110, warmer than the room and cooler than your hand. Carrier says the same on its own support pages. If the house is holding temperature, nothing is wrong.
The outdoor unit steams and the fan stops for a few minutes. That is a defrost cycle. On a damp 35 degree day, which is most of a Reston winter, frost builds on the outdoor coil and the unit briefly runs backwards to melt it. Steam, a hiss, cool air indoors for a few minutes, then normal. Manufacturers put it at five to fifteen minutes, as often as every half hour when it is raw.
It runs for forty minutes at a stretch. Heat pumps are built for long, steady cycles. A furnace mindset expects short blasts.
“Aux” or “Em Heat” shows up on the thermostat on a cold night. Below the balance point, which Carrier puts around 30 to 35 degrees for a typical unit, the electric strips help out. On a 20 degree January morning that is the system working as designed.
And the four that are not
Ice that never clears. Frost is normal, a block of ice is not, and a unit still iced at noon means defrost is not happening. Defrost board most often, $450 to $1,150. Switch to Emergency Heat and call, because running it iced bends the fan blades and eventually damages the coil.
Aux heat running all the time, even in the 40s. The heat pump is not carrying the load and the resistance strips are, which is the most expensive way to heat a house in Virginia. You will see it on the Dominion bill before you feel it in the room. Low refrigerant, a failing compressor, a stuck reversing valve, or a thermostat that was never configured for a heat pump.
It cools when it should heat. Reversing valve stuck, or a thermostat wired wrong. Heat pump thermostats use an O or B wire to flip that valve, and a thermostat installed by somebody who did not know that runs backwards all winter. The thermostat fix is $300 to $640.
The outdoor unit hums but the fan does not turn. Capacitor, $240 to $370, and the single most common failure on any outdoor unit.
What it costs here, and why Reston runs higher
Heat pump calls tend to run higher than furnace calls, and that is the equipment rather than a Reston surcharge. A furnace with no heat is very often a $95 flame sensor cleaning. A heat pump with no heat usually means gauges, electrical readings, and a control board or a refrigerant question, and those start higher.
- Diagnostic visit: about $99.
- Capacitor $240 to $370. Contactor $290 to $425.
- Thermostat, replaced with one that knows it is on a heat pump: $300 to $640.
- Defrost board: $450 to $1,150.
- Refrigerant added, one to three pounds: $190 to $740. If it is low, it leaked.
- Outdoor fan motor: $1,100 to $1,500. Blower motor: $670 to $2,400.
- Compressor, out of warranty: $2,200 to $5,100. Under parts warranty: $1,900 to $2,500.
One thing worth knowing on refrigerant. R-410A, in nearly every system installed from about 2010 through 2024, is being phased down under federal law, and the price has roughly doubled in two years. The EPA is clear that you can keep repairing an R-410A system, including replacing the compressor. But a refrigerant heavy repair on an older heat pump leans toward replacement harder than it did three years ago, and a slow leak you could nurse through a cooling season leaves you with no heat in January, because a heat pump needs that refrigerant in both directions.
When to replace
Heat pumps run year round in this climate, so a twelve year old heat pump has the hours of a twenty year old furnace; ASHRAE’s median service life is fifteen years and ENERGY STAR’s replacement threshold is ten. Under eight years, repair. Over fourteen, a compressor or a reversing valve is replacement money, and a new heat pump system starts at $8,698 installed.
The estimator gives you the installed range for your size in two minutes. If your cluster has no ducts worth saving, or you are heating an addition that never worked right, the ductless estimator prices that instead: one zone $7,000 to $10,000, two $11,000 to $15,000, three $12,500 to $18,000.
Two things to do in October
Run the heat for an hour and watch the outdoor unit actually start. A heat pump that will not come on in October is a Tuesday appointment; the same fault on the first 20 degree night is an evening call behind everyone else’s.
Then clear around and under the outdoor unit, including leaves and mulch. A heat pump drains defrost water out the bottom, and a unit sitting in wet leaves or on a pad that has settled into the mud freezes itself to the ground by February. In wooded Reston this is the most common thing we find and the easiest to prevent.
SwiftPro repairs heat pumps and furnaces across Reston. Call (703) 997-9757, book online, or see the Reston furnace repair page. How a heat pump handles a Virginia winter is the longer read.
