How much does a space heater cost per month?

The only formula you need

Every plug-in electric heater — ceramic, oil-filled, fan, or infrared — costs the same for the same wattage and runtime, because they all convert electricity to heat with essentially no loss. The formula is: watts ÷ 1000 (to get kilowatts) × hours run × your price per kilowatt-hour.

There is no version of this where a heater is 'more efficient' at turning power into warmth. What differs between heaters is how well that heat reaches you — a ceramic space heater with a fan pushes warm air across a room faster than a passive radiant panel, so it can do the job in fewer minutes even though the per-hour cost is identical. How the WellHeater works explains why the thermostat and timer, not the element, decide what you actually pay.

How we work these figures out

Take an 800W heater at $0.17/kWh, the current US residential average. Per hour: 800 ÷ 1000 = 0.8 kW, so 0.8 × 1 hour × $0.17 = $0.136, rounded to about $0.14/hour.

Per day at 8 hours: 0.8 × 8 × $0.17 = $1.088, about $1.09/day. Per month at 30 days of that same 8-hour pattern: $1.088 × 30 = $32.64. Change the wattage, the hours, or the rate and you can redo this math yourself with a calculator in ten seconds — nobody needs to take a heater's cost on faith.

Cost by wattage, at $0.17/kWh

How electricity rate changes the same heater

Wattage gets most of the attention, but your local rate per kWh swings the bill just as much. An 800W heater run 8 hours a day looks very different in a low-cost region than in a state with expensive power.

Why the whole-house comparison matters more than the heater

The number that actually decides whether a heater saves money is not on this page — it's your furnace or boiler's cost to heat rooms you're not using. If turning the thermostat down 3-4°F and running an 800W heater in the one room you occupy lets the central system cycle less, the household total usually drops even though the electric bill for that room rises.

This only works if you actually turn the main system down. Running a space heater on top of an unchanged thermostat setting adds cost with no offset — see our page on the cheapest way to heat a room for the sequence that makes zone heating pay off.

Five ways to lower the monthly number

• Use the timer and auto shut-off rather than running continuously — most rooms hold warmth for a while after power cuts.
• Set a thermostat mode instead of leaving the unit on its highest fixed setting.
• Close the door of the room you're heating so the volume of air being warmed stays small.
• Keep the washable filter clean — restricted airflow makes any heater work harder for the same warmth.
• Turn the central thermostat down at the same time you switch the space heater on, not afterward.

What drives your real number up or down

Room size and insulation matter more than any spec sheet. A drafty 200 sq ft room needs more running time than an insulated 100 sq ft room even at the same wattage, because heat is constantly leaking back out. See how many watts a space heater uses for matching wattage to room size before you worry about the bill.

Climate and how many hours a day you're actually in the room also swing the total more than the heater choice itself. Someone running a heater 3 hours an evening in a mild climate will land well under half of someone running the same unit 10 hours a day through a cold snap.

Comparing against the WellHeater specifically

WellHeater is an 800W PTC ceramic unit, so it sits in the middle row of the wattage table above at whatever rate you pay locally. It reaches warm air in about 60 seconds and covers up to 130 sq ft, and its touch panel and remote make it easy to set a timer instead of leaving it running — see the current official-store price and full specs in the manual.