How Much Does Heating Cost? By Fuel, Per Month, With Math

Nobody budgets for heat in July. Then the first cold week arrives, a space heater comes out of the closet, and the biggest wattage in the house starts running the longest hours. That combination is the whole story of winter electric bills. A 1,500 W heater draws half again what a microwave does, but a microwave runs eight minutes and the heater runs eight hours. At the US average rate of about 17.5¢/kWh, one heater on that schedule costs $63 a month. Put one in three rooms and you are at $189, quietly passing what plenty of whole-home systems cost, one harmless-looking $2.10 day at a time.

Two mistakes produce most of the January bill shock. The first happens in the store: buying a heater because the box says "energy saving," when every electric resistance heater of a given wattage costs exactly the same to run, whatever it looks like and whatever it sells for. The second happens at home: pricing heat by the room and the day instead of the house and the season. Both fall to one line of arithmetic, and this guide grinds through it with real numbers — per month, per season, and fuel by fuel — so you can size the winter in October instead of discovering it in January.

The quick answer

At the US average rate of $0.175/kWh, over a 30-day month:

Read the first two rows twice. A 750 W heater for 8 hours and a 1,500 W heater for 4 hours are the same 180 kWh and the same $31.50, because the cost lives in the product of watts and hours. Halve either factor and you halve the bill; double both and it quadruples. The last row is the only genuine discount in the table, and it comes from physics rather than marketing — more on that below.

One caution before you take a row and run: the table uses the national average rate, and rates vary widely by state. Every dollar figure here scales in direct proportion to the rate on your own bill, so a household paying double the average pays double every number in this guide. Pull your real rate before you budget anything.

The formula the calculator runs

The heating cost calculator runs two lines:

• kWh = (watts ÷ 1000) × hours per day × days
• cost = kWh × rate

That is the same energy-times-rate math as any electric load — a lamp, a fridge, a games console. Nothing about heat changes the arithmetic; what changes is the size of the inputs. Heating combines the biggest wattages a household plugs in with the longest runtimes anything ever runs, which is why the same formula that prices a phone charger at pennies prices a heater at real money. If you want the general version of this math, with rates, bills, and phantom loads, our guide to how much electricity costs covers the kilowatt-hour from the ground up.

Four inputs drive the calculator. The wattage slider runs 500 to 5,000 W, which spans a small personal heater to a hardwired 240 V shop unit. Hours run 0.5 to 24, days run 1 to 365 — that last range is deliberate, because the days input is how you turn a month estimate into a season estimate. The rate field defaults to $0.175 with a pointed hint: use the number from your own bill. The results panel gives you the total cost for the period, the energy in kWh, the cost per day, and the cost per standard 30-day month.

Worked example: the $63 default month, line by line

Grind through the defaults by hand once, because after this the calculator is just saving you the arithmetic.

A 1,500 W heater, 8 hours a day, for 30 days, at $0.175/kWh:

1. Watts to kilowatts: 1500 ÷ 1000 = 1.5 kW.
2. Energy per day: 1.5 × 8 = 12 kWh a day.
3. Energy for the month: 12 × 30 = 360 kWh.
4. Cost: 360 × $0.175 = $63.00 — which is $2.10 a day.

Notice that the rate enters only at the last step. The 360 kWh is fixed by the heater and the schedule; the rate just prices it. That is why the calculation is so portable — whatever your utility charges, steps 1 through 3 are identical, and step 4 is one multiplication with your own number.

Each of the calculator's outputs earns its place. The period total is the budgeting number. The cost per day is the comparison number — $2.10 a day puts the heater beside anything else you run and makes the trade-offs concrete. And the kWh figure is your audit trail: 360 kWh is large enough to show up plainly on the usage graph printed on your electric bill, so when February's statement arrives you can check the estimate against reality and see exactly how much of the jump was the heater.

Now scale it up. A 5,000 W shop or garage heater on the same 8-hour schedule is 40 kWh a day, 1,200 kWh for the month, and $210 at the average rate. Wattage is a straight multiplier: three and a third times the watts, three and a third times the bill. There is no clever setting or premium brand that changes this. For resistance heat, watts and hours are the entire cost model.

Every 1,500 W heater costs exactly the same to run

This is the myth worth clearing before you spend anything. Space heaters are sold hard on efficiency: ceramic elements, oil-filled radiators that "keep radiating after shutoff," infrared panels that "heat objects, not air." The prices run from twenty dollars to two hundred, and the marketing implies the expensive end pays for itself on the bill.

It does not, and cannot. Every electric resistance heater converts electricity to heat at 100% efficiency — a $20 ceramic tower and a $200 "infrared" panel both turn 1,500 watts into exactly the same amount of heat, because there is nowhere else for the energy to go. Run either one 8 hours a day for a month and the meter records the same 360 kWh and the bill says the same $63.00. The pricier heater is quieter, or prettier, or has a nicer thermostat. It is not cheaper to run.

The oil-filled radiator deserves one extra sentence, because its pitch sounds the most plausible. Yes, it stays warm after it switches off — but that heat was bought while the element ran, stored in the oil, and released a little later. It changes when the warmth arrives, not how much electricity was purchased to make it. Your meter integrates everything; the timing shuffle never appears on the bill.

The useful corollary: since wattage and runtime are the only levers, they are also the only savings. A heater with a good thermostat that cycles off when the room holds temperature saves real money — not because the heater is efficient, but because it reduces the hours. A lower wattage setting saves money because it reduces the watts. Everything that genuinely cuts a resistance-heating bill is one of those two things wearing a feature name.

The per-room trap

$2.10 a day sounds harmless. That framing is exactly how space heaters get expensive, because nobody runs one heater for one month and stops. They run one per occupied room, all season.

Do the multiplication the marketing skips. One room at 8 hours a day is $63 a month. A second room makes it $126. Three rooms make it $189 a month — and at that point you are paying more than many whole-home systems cost to run, with three noisy point sources instead of even heat. The per-room math is linear and merciless: every additional heater is another full $63 on the same schedule.

Space heaters do have a legitimate win condition, and it is worth stating precisely: brief, targeted warmth in the one room you actually occupy. An hour of 1,500 W is 1.5 kWh — about 26 cents at the average rate. Heating your home office for a workday morning while the rest of the house stays cold is the use case where a space heater beats everything, because you are buying heat for one small room instead of the whole house. The trap is mission creep: the heater that warmed one desk for two hours in November is warming three rooms for eight hours by January, and the bill has quietly climbed an order of magnitude.

The honest decision rule falls out of the formula. Short hours, one room: the space heater wins. Long hours, multiple rooms: it loses to almost anything, and the rest of this guide is about what it loses to.

Heat pumps: the only way to beat 100%

Resistance heat's 100% efficiency sounds unbeatable until you realize it is a ceiling, not an achievement. A heat pump does not make heat from electricity — it moves heat that already exists in the outdoor air into your house, running a refrigeration cycle in reverse. Moving heat takes far less energy than making it, so a heat pump delivers two to four units of heat per unit of electricity. That ratio is the coefficient of performance, or COP, and it is the single most consequential number in home heating.

At a COP of 3, the same warmth our default heater made from 360 kWh takes only 360 ÷ 3 = 120 kWh, which costs $21 instead of $63. Same rooms, same temperature, a third of the bill.

Scale that to a real winter and the gap gets serious. Take a home whose heat demand is 1,000 kWh a month — a fair winter month for a mid-size house on electric heat. On resistance heat that is 1,000 × $0.175 = $175.00 a month. A COP-3 heat pump draws only 333.3 kWh for the same warmth: $58.33. The saving is $116.67 a month, roughly $1,400 a year, and a COP-4 unit stretches it to $131.25 a month. The heat pump savings calculator runs exactly this comparison from your own monthly kWh and rate.

One honest caveat: COP falls as the outdoor temperature drops, because there is less ambient heat outside to move. A unit rated COP 3 in mild weather can land well below that on a deep-winter night, and many heat pumps fall back to built-in resistance strips — COP 1, no better than baseboards — in extreme cold. If your winters are harsh, run the savings math again with a conservative COP and treat the nameplate figure as the mild-weather best case. Even discounted, the heat pump still wins against resistance heat; the only question is by how much.

Where gas fits in

Gas heating runs on different units — therms instead of kilowatt-hours — which is exactly why most gas-versus-electric arguments go nowhere. The fix is one conversion: a therm is 100,000 BTU of heat, which is about 29.3 kWh. Put both fuels in the same units of delivered warmth and you can price them head to head.

Two adjustments keep the comparison honest. Gas furnaces lose some heat up the flue, so the gas you buy is the useful heat divided by the furnace's AFUE — a modern condensing furnace sits around 0.90 to 0.98, older units lower. And electric systems divide by COP, which is 1 for resistance and 2 to 4 for a heat pump. The gas vs electric heating calculator runs both sides for the identical quantity of heat.

Here is what its representative numbers look like for 50 therm-equivalents of useful warmth — a fair chunk of a heating season:

• Gas furnace at 0.95 AFUE and $1.50/therm: (50 ÷ 0.95) × $1.50 = $78.95
• Heat pump at COP 3 and $0.175/kWh: 50 × 29.3 = 1,465 kWh, ÷ 3 = 488.3 kWh, × $0.175 = $85.46
• Resistance heat at COP 1: the full 1,465 kWh × $0.175 = $256.38

Two lessons hide in those bars. First, gas and a modern heat pump run nearly level — $6.51 apart on these rates, a margin small enough that your local gas price or a better COP flips the winner. Cheap gas against expensive electricity favors the furnace; the reverse favors the heat pump. There is no national answer, only your two bills. Second, resistance heat loses to both by a factor of three. "100% efficient" and "cheap to run" are different claims, and resistance heat is only ever the first.

One more thing your gas bill hides: a fixed monthly service charge rides on top of the per-therm rate, so your true all-in cost per therm is higher than the printed supply rate — 50 therms at $1.50 plus a $12 service charge works out to $1.74 a therm, not $1.50. The natural gas cost calculator rebuilds the whole bill and hands you that all-in figure, which is the right number to carry into any fuel comparison.

Budget the season, not the month

Everything so far priced a 30-day month, and a heating season is not 30 days. Depending on your climate it is three to five months of meaningful runtime, and the days input on the calculator exists precisely so you can price the whole thing in one pass.

The math scales linearly, so a season is the same worked example with a bigger days input. Run the 120-day version by hand once:

1. Energy per day: (1500 ÷ 1000) × 8 = 12 kWh, exactly as before.
2. Energy for the season: 12 × 120 = 1,440 kWh.
3. Cost: 1,440 × $0.175 = $252.00 for one room's winter.
4. Scale to the plan: three rooms is 3 × $252 = $756; a milder 90-day season is 1,080 kWh and $189 per room; a COP-3 heat pump covering that one room's 120 days draws 1,440 ÷ 3 = 480 kWh and costs $84.

That $756 figure is the one to sit with. It is the realistic cost of the casual "we'll just use space heaters this winter" plan for a three-room household, and almost nobody who makes that plan in October has seen it as a single number. Whether it is a bad number depends on the alternative — it may still beat installing something — but it should be a decision, not a surprise.

A practical seasonal workflow, in order: pull the real rate off your latest electric bill. Be honest about hours — "on all evening" is five or six hours, not twelve, and a thermostat that cycles the heater cuts effective runtime further. Set the days to your actual season: 90 for a mild-winter region, 120 to 150 for a cold one. Then run the calculator once per scenario you are genuinely considering — the space-heater plan, the heat-pump plan — and compare season totals, not month totals. Five minutes of slider-dragging in October is the entire exercise.

One thing this guide deliberately does not do is tell you what capacity you need — how many watts or BTU it takes to actually keep a given room warm. That is a sizing question, driven by the room's volume, insulation, and climate, and it is a different calculation from pricing the runtime. Size first, then cost what you sized.

Common mistakes to avoid

• Buying a "cheaper-to-run" resistance heater. There is no such thing at a given wattage. Every 1,500 W unit is 100% efficient and costs the same $63 on the default schedule.
• Using the national average rate. Rates vary widely by state, and every figure scales with your rate. Read your bill.
• Counting plugged-in time as runtime. A heater that cycles on a thermostat runs fewer effective hours than the clock says; a heater "on all evening" ran six hours, not twenty-four.
• Pricing one room and running three. The per-room math is linear: three rooms at 8 hours is $189 a month, every month, all season.
• Budgeting one month when the season is four. Multiply by the real length of your winter — $63 a month reads very differently as $252 a season, per room.
• Comparing fuels by efficiency instead of delivered-heat cost. Resistance heat is 100% efficient and still costs three times what gas or a heat pump pays for the same warmth.

The whole subject compresses to one line: watts ÷ 1000, times honest hours, times the real length of your season, times the rate on your own bill. Run it for the heater you have, then run it once more for a heat pump at COP 3, and let the two totals argue it out. The heater that looks cheap in the store and the heater that is cheap in February are rarely the same machine.