Guide · Cost
The hourly number is small enough to ignore. The monthly one is not, which is why this is the table that changes behavior.
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A 1,500 W heater running 8 hours a day for a 30-day month uses 360 kWh and costs about $66 at the U.S. average rate of 18.34¢/kWh. Running 24 hours a day it uses 1,080 kWh and costs about $198.
The rate behind every figure on this site
18.34¢per kilowatt-hour
U.S. residential average for June 2026. EIA, Electric Power Monthly, Table 5.6.A, released August 26, 2026.
This is the most recent month EIA has published. Residential rates move seasonally and vary enormously by state — from roughly a dime per kilowatt-hour in parts of the South to more than 40¢ in Hawaii — so treat it as a national reference point, not as your rate.
| Wattage | 4 h/day | 8 h/day | 12 h/day | 24 h/day |
|---|---|---|---|---|
| 750 W | $16.51 | $33.01 | $49.52 | $99.04 |
| 1,000 W | $22.01 | $44.02 | $66.02 | $132.05 |
| 1,500 W | $33.01 | $66.02 | $99.04 | $198.07 |
Computed at 18.34¢/kWh — the U.S. residential average for June 2026 (EIA, Electric Power Monthly, Table 5.6.A, released August 26, 2026). Your rate is on your own bill; substitute it and the arithmetic still holds. Monthly figures are 30-day months at full output; a thermostat that cycles will reduce them.
The arithmetic behind any cell: (watts ÷ 1,000) × hours per day × 30 days × rate. For the headline case, 1.5 kW × 8 h × 30 = 360 kWh, and 360 × $0.1834 = $66.02.
“How much does it cost to run a space heater 24/7” is one of the most-searched versions of this question, and it deserves a straight answer rather than a hedge: at full output, about $198 a month for a 1,500 W unit at the U.S. average rate. In a high-rate state it is well over $300.
But the more useful answer is that continuous running is almost always a symptom. A thermostat-controlled heater in a correctly sized room does not run 24/7 — it cycles. If yours genuinely never stops, one of three things is true: the room needs more watts than the heater has (check the sizing), the thermostat is a dial you have set to maximum rather than to a temperature, or the room is losing heat as fast as the heater makes it, which is a draft problem rather than a heating one.
The table above is the ceiling. Real usage lands lower for two reasons: the heater cycles, and you do not use it every day of the month. A heater used on the 20 genuinely cold evenings of a shoulder month, for five hours each, at a 50% duty cycle, is 1.5 kW × 5 h × 20 days × 0.5 = 75 kWh, or about $13.75. The same heater in a cold snap, running eight hours a night for 30 days at a 60% duty cycle, is 216 kWh, or about $39.60.
Both of those are computed from stated assumptions you can change. We are not going to publish a single “typical monthly cost”, because the honest range spans an order of magnitude and depends entirely on facts about your house that we do not have.
Ranked for fit, not for hype. Coverage and current draw are computed from each unit’s published wattage. Tap a row for the full write-up, or go straight to the listing.
| # | Product | Best for | Covers | Draw | Price |
|---|---|---|---|---|---|
| 1 | De'LonghiNo photo De'Longhi Dragon DigitalThe oil-filled radiator with a programmable timer, which is the version that matters overnight: it can bring a bedroom up before you wake and shut itself off, unattended, without you leaving it running all night. | Overnight, on a schedule | 150 sq ft | 12.5 A | Check price on Amazon |
| 2 | LaskoNo photo Lasko 754200The 900 W low setting is the whole point: it is the rare listing that publishes both settings, so you can compute what the cheap mode actually costs instead of guessing. | One person at one desk | 150 sq ft | 12.5 A | Check price on Amazon |
| 3 | VornadoNo photo Vornado VMHi600The metal-cabinet version of the same 1,500 W: what you are buying is the inlet grill, the digital thermostat and the timer, not extra heat. | A metal cabinet and a real thermostat | 150 sq ft | 12.5 A | Check price on Amazon |
Coverage computed at 10 W/sq ft, average insulation, 8 ft ceiling. Draw computed as watts ÷ volts. Neither figure is a manufacturer claim.
Top pick · Overnight, on a schedule
The oil-filled radiator with a programmable timer, which is the version that matters overnight: it can bring a bedroom up before you wake and shut itself off, unattended, without you leaving it running all night.
| Published specification | |
|---|---|
| Rated power | 1,500 W at 120 V |
| Controls | Digital, with a programmable timer |
| Dimensions | 16" x 10" x 26" |
| Fluid | Permanently sealed diathermic oil |
| Maker's coverage claim | None published — sold as a full-room heater |
| Heat type | Oil-filled |
| Maker’s coverage claim | None published — the coverage figure above is ours |
| Safety listing | No listing mark published in the listing text; verify the UL or ETL mark on the rating plate. |
Who it is for
A bedroom where the heater needs to run on a schedule rather than all night, and where noise would wake you.
What it is not for
A room you need warm in five minutes, or a tight space where a hot 26-inch radiator cannot keep 3 feet of clearance.
Sources for this entry
2 · One person at one desk
The 900 W low setting is the whole point: it is the rare listing that publishes both settings, so you can compute what the cheap mode actually costs instead of guessing.
| Published specification | |
|---|---|
| Rated power | 1,500 W high / 900 W low, at 120 V |
| Maker's coverage claim | None published — sold as a desktop heater |
| Thermostat | Adjustable, 11 settings |
| Size | 9.2" tall |
| Other modes | Fan-only |
| Heat type | Ceramic (PTC) |
| Maker’s coverage claim | None published — the coverage figure above is ours |
| Safety listing | No listing mark published in the listing text; check the rating plate for UL or ETL. |
Who it is for
A desk, a small office, a dorm room — somewhere you want heat on a person rather than in a room.
What it is not for
Overnight or unattended use, and not a nursery. Without a published tip-over cutoff it does not belong on carpet next to a bed.
Sources for this entry
3 · A metal cabinet and a real thermostat
The metal-cabinet version of the same 1,500 W: what you are buying is the inlet grill, the digital thermostat and the timer, not extra heat.
| Published specification | |
|---|---|
| Rated power | 1,500 W at 120 V |
| Heat settings | 2, plus fan-only |
| Controls | Digital thermostat, remote, 1–12 hour timer |
| Housing | Metal cabinet with a metal inlet grill |
| Maker's coverage claim | None published |
| Heat type | Fan-forced |
| Maker’s coverage claim | None published — the coverage figure above is ours |
| Safety listing | No listing mark published in the listing text; check the rating plate for UL or ETL. |
Who it is for
A main living space where the heater is going to be visible and permanent, and where a timer and a real thermostat are worth paying for.
What it is not for
A nursery or anywhere small hands reach. A metal cabinet gets warm, and no child lock is published.
At 18.34¢/kWh, a 1,500 W heater running 8 hours a day for 30 days adds about $66 at full output — and roughly $33–$40 once a working thermostat cycles it. Four hours a day is about $33 at full output.
About $198 a month for a 1,500 W unit at the U.S. average rate of 18.34¢/kWh, at full output. Continuous running usually indicates the heater is under-sized for the room rather than that continuous running is necessary.
For one room, usually yes — provided you turn the main system down at the same time. Running a heater in addition to an unchanged furnace setting always adds cost.
A 1,500 W heater uses 1.5 kWh per hour of running. Eight hours a day for 30 days is 360 kWh; 24 hours a day is 1,080 kWh. Multiply by your rate for the cost.
Cost per hour for any wattage at any rate — the calculator, the formula and the full grid.
Per-BTU arithmetic for gas, oil and electric — and the one condition that decides the answer.
All electric heaters are 100% efficient. These are picked on the three things that actually cut the bill.
The official guidance, the data behind it, and the timer setup that gets you warmth without unattended running.
A correction, not a product pick: equal wattage means equal cost, and here is what actually varies.
Room dimensions in, wattage and BTU out — with both corrections applied and the formula visible.