What determines heat-pump running costs in Washington, DC?

Your running cost is the electricity the heat pump uses times your Pepco rate, plus any hours on backup heat and the fixed charges you keep paying. On the DC Office of the People’s Counsel calculator components, every 100 kWh of added winter use costs about $15.40 before riders and taxes. At Perennial DC Heat Pumps we install ducted systems across Washington, DC, and this guide shows you how to run the numbers on your own bills.

Is the price tag the same as what it costs to run?

No, and mixing them up is how payback figures go wrong. The installed price is a one-time cost for the equipment and agreed work; our typical range for a whole-home ducted system is $8,000 to $18,000 before rebates. Running cost is what the system draws from the meter every month after that.

Our installed-cost guide covers the project budget. If any proposal you get shows a payback period, it should show four inputs: the gross price, the rebate you actually expect, your current heating energy and the rates applied. A heavy-up left out, or a conversion rebate that never arrives, can move the answer by thousands of dollars.

Why does a heat pump cost more to run on the coldest days?

Because its efficiency falls as the air outside gets colder. Coefficient of performance (COP) is heat delivered divided by electricity used. Electric resistance heat has a COP of 1: one kWh in, one kWh of heat out, which is 3,412 Btu. A heat pump moves heat rather than making it, so its COP sits above 1 in most conditions.

The colder it gets, the harder the compressor works to lift heat across the gap. ENERGY STAR’s heating design temperature for Washington, DC is 14°F, and how a system performs near that point matters more for your winter bills than a rating taken at 47°F. Illustrative arithmetic: delivering 30 kWh of heat at a COP of 3 takes 10 kWh; at a COP of 2 it takes 15 kWh. Our cold-climate page explains why we check low-temperature output separately from efficiency.

What’s on your Pepco and Washington Gas bills?

The DC Office of the People’s Counsel (OPC) publishes calculator components for both utilities. Rates change season to season, so read the table as the shape of your bill and take today’s numbers from your own statement.

Riders and taxes go on top of both bills. Our project assessment organizes your system details, but it doesn’t look up a tariff from your ZIP code.

How to compare gas and electric heat on your own bills

Illustrative arithmetic, using your own usage: for every 100 kWh added in a month already above 400 kWh, the per-kWh components come to 100 × ($0.102 + $0.018 + $0.034) = $15.40. For every 100 therms of gas, the per-therm components come to 100 × ($0.69 + $0.73 + $0.07) = $149. Neither figure includes riders or taxes.

To compare the two, convert both to delivered heat. One therm is 100,000 Btu, or about 29.3 kWh. A furnace burning 100 therms at 80% efficiency delivers about 2,344 kWh of heat. Divide that by the heat pump’s seasonal COP to get the kWh it would need for the same heat: about 938 kWh at a COP of 2.5, or 1,172 kWh at a COP of 2. Then apply the per-kWh rate from your own bill and set it beside your gas cost.

Why did the bill jump when backup heat came on?

Because backup heat costs far more per unit of heat than the compressor. A 10 kW resistance strip running for one hour uses 10 kWh, about $1.54 on the per-kWh components above, and delivers 34,120 Btu. A heat pump delivering the same heat at a COP of 2.5 would use 4 kWh. Every hour the strip carries the load instead of the compressor costs about 2.5 times as much for that heat.

Backup runs during defrost, during big thermostat recoveries and when it gets cold enough that the heat pump alone can’t meet the load. Our defrost and auxiliary guide explains each trigger. With dual fuel, the switchover temperature decides when gas, at roughly $1.49 per therm in components, takes over from electricity, and we put that setting in your written estimate.

Will you still pay a gas bill after the furnace goes?

Only if the account stays open. The Washington Gas customer charge of $19.05 a month is $228.60 a year, and it stays if a gas range or water heater remains connected after the furnace goes. The Pepco customer charge of $17.09 a month applies either way, so it drops out of the comparison.

Compare like with like: the same rooms, the same thermostat settings and the same months for both options. If you are adding air conditioning to rooms that never had it, the extra summer kWh is new comfort, not a heating cost. Our heat pump versus furnace guide separates the equipment decision from the gas-account decision, and the rebate guide explains why the DCSEU conversion tiers need the fuel system removed.

How sure can anyone be about next winter’s bill?

Not completely, so we show you how the result moves when the COP, the rates or the hours of backup change. Nobody can fix next winter’s weather or next season’s rates. If any estimate shows you one annual saving figure with no inputs, ask for the kWh, therms, COP and rates behind it.

Our quote checklist has a line for that calculation, and the sizing guide explains how capacity at 14°F decides how often backup runs. For a furnace conversion, request an estimate with twelve months of Pepco and Washington Gas bills; we use them to turn the arithmetic above into a range for your house.