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.
The top of that range is worth seeing on its own: a single 1,500 W heater left running around the clock comes to roughly $198 a month. How long you can run a space heater sets out the 24/7 figures beside the eight- and twelve-hour ones, and explains why a heater that never cycles off is telling you it is undersized.
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'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 | $189.95 · Check on Amazon |
| 2 |  Lasko 754201The 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 | $49.99 · Check on Amazon |
| 3 |  Vornado VMHi500The current top of Vornado's metal line: auto-climate control, two LED displays and a 1-12 hour timer in a cool-touch metal box, backed by five years. | A metal cabinet that stops on its own | 150 sq ft | 12.5 A | $135.99 · Check 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 24-hour programmable timer |
| ECO function | Regulates power and temperature rather than running at full output |
| Dimensions | 16" x 10" x 26" |
| Fluid | Permanently sealed diathermic oil |
| Safety | Child lock, thermal cut-off |
| 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 |
| Thermostat | Adjustable dial; 2 heat settings plus fan-only |
| Size | 9.2 x 7 x 6 in, 2.93 lb |
| Cord | 6 ft (Lasko's published figure) |
| Safety | Tip-over switch, overheat protection, cool-touch housing |
| Warranty | 3 years |
| Heat type | Ceramic (PTC) |
| Maker’s coverage claim | 100 sq ft |
| Safety listing | ETL listed, per Lasko's published specification — one of the few in this roundup that names a mark rather than leaving it to the rating plate. |
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
A nursery, and not unattended use. It publishes a tip-over switch and overheat protection, but no child lock — and the USFA's advice to switch a heater off when you leave the room applies to every unit on this site, listed or not.
3 · A metal cabinet that stops on its own
The current top of Vornado's metal line: auto-climate control, two LED displays and a 1-12 hour timer in a cool-touch metal box, backed by five years.
| Published specification | |
|---|---|
| Rated power | 1,500 W at 120 V (retail listings; Vornado publishes settings, not watts) |
| Heat settings | 2, plus fan-only |
| Thermostat | Auto-Climate Control, digital |
| Timer | 1–12 hours |
| Display | Two LED displays, for reading it from across the room |
| Housing | Cool-touch, powder-coated gloss metal cabinet with cord storage |
| Safety | Tip-over protection and a 2-stage auto shutoff |
| Warranty | 5-year satisfaction guarantee |
| Heat type | Fan-forced |
| Maker’s coverage claim | None published — the coverage figure above is ours |
| Safety listing | Vornado publishes tip-over protection and a 2-stage auto shutoff but does not name a listing mark; check the rating plate. |
Who it is for
A living room or bedroom where the heater is permanent and visible, and where a real thermostat, a timer and a cool metal shell are worth paying for over a plastic tower.
What it is not for
A nursery, because no child lock is published; and not silence, which means an oil-filled radiator instead.
Sources for this entry
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.
The only feature that actually cuts the bill, because it is the only one that turns the heater off.
No time limit on the appliance. The three real limits are the circuit, the bill, and the unattended-use advice.