Guide · Watts
Almost every plug-in heater in America is 1,500 watts, and the reason is not the heater. It is the outlet.
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Most plug-in space heaters draw 1,500 watts on high, with a low setting of 750 to 900 watts. 1,500 W is the effective ceiling because a 120 V, 15 A branch circuit supports 12 A of continuous load, which is 1,440 W.
A standard U.S. wall outlet is fed by a 120 V branch circuit protected at 15 A, or sometimes 20 A. Electrical code treats a load that runs for three hours or more as continuous, and requires the branch circuit and its overcurrent device to be rated at not less than 125% of that continuous load (NFPA 70, Article 210.19(A)(1) and 210.20(A)).
Turn that around: a continuous load may not exceed 80% of the breaker rating. On a 15 A circuit that is 12 A, and 12 A × 120 V = 1,440 W. On a 20 A circuit it is 16 A, or 1,920 W.
So 1,500 W is the number the industry settled on: it is the largest round figure that a 15 A outlet will physically deliver without tripping, and it is slightly above the continuous allowance — which is a wrinkle almost nobody publishes and which we work through here.
| Watts | Amps at 120 V | Covers (average room) | Cost per hour |
|---|---|---|---|
| 500 W | 4.2 A | 50 sq ft | 9.2¢ |
| 750 W | 6.3 A | 75 sq ft | 13.8¢ |
| 900 W | 7.5 A | 90 sq ft | 16.5¢ |
| 1,000 W | 8.3 A | 100 sq ft | 18.3¢ |
| 1,200 W | 10.0 A | 120 sq ft | 22.0¢ |
| 1,500 W | 12.5 A | 150 sq ft | 27.5¢ |
Amps = W ÷ 120. Coverage at 10 W/sq ft, average insulation, 8-ft ceiling. Cost at 18.34¢/kWh (EIA, June 2026).
That table is the whole of this site in one place: the wattage decides the amps, the amps decide the circuit, the wattage decides the coverage, and the wattage decides the cost. Everything else is packaging.
The low setting is under-used, and the reason is a misconception: people assume a heater on low takes proportionally longer to heat the room and therefore costs the same overall. In a room the heater can actually hold, that is not what happens. Once the room is at temperature, both settings are just cycling — and on low it cycles at a lower power, so it costs less per hour of running.
The rule of thumb: match the setting to the room's requirement, not to the heater's maximum. A 100 sq ft office needs about 1,000 W, so a 900 W low setting will hold it once it is warm. Use high to get there, then drop to low.
| Wattage | 8 h/day |
|---|---|
| 750 W | $33.01 |
| 900 W | $39.61 |
| 1,500 W | $66.02 |
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.
Some listings advertise a heater as “equivalent to 1,500 W” while rating it lower. What that generally means is that the unit is radiant and points at you, so it feels comparable at close range. That can be genuinely true as a comfort claim — but it is not equivalent output, and it will not hold a room the way the wattage it is compared to would. Read the rated wattage on the specification, size the room from that, and treat the comparison as marketing.
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 | 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 |
| 2 | HoneywellNo photo Honeywell HCE200WA compact 1,500 W ceramic that publishes the two features cheap small heaters usually omit — a tip-over switch and overheat protection — in a body the size of a shoebox. | The smallest sensible footprint | 150 sq ft | 12.5 A | Check price on Amazon |
| 3 | Dr. Infrared HeaterNo photo Dr Infrared DR-968The one listing in this category that publishes its amp draw and its noise level, which is exactly the arithmetic everyone else leaves you to do — 12.5 A and 39 dB, both stated. | The published numbers | 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 · 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
2 · The smallest sensible footprint
A compact 1,500 W ceramic that publishes the two features cheap small heaters usually omit — a tip-over switch and overheat protection — in a body the size of a shoebox.
| Published specification | |
|---|---|
| Rated power | 1,500 W at 120 V |
| Heat settings | 2, plus an adjustable thermostat |
| Safety | Tip-over switch, overheat protection, cool-touch housing |
| Maker's coverage claim | None published — sold as a personal heater |
| 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 the UL or ETL mark. |
Who it is for
A desk, a small bedroom or a home office where the heater has to be out of the way but still needs a tip-over cutoff.
What it is not for
A large or open-plan room, and not unattended overnight use — no timer, no lock.
Sources for this entry
3 · The published numbers
The one listing in this category that publishes its amp draw and its noise level, which is exactly the arithmetic everyone else leaves you to do — 12.5 A and 39 dB, both stated.
| Published specification | |
|---|---|
| Rated power | 1,500 W at 120 V |
| Current draw | 12.5 A (published) |
| Noise | 39 dB (published) |
| Element | Infrared quartz tube plus PTC |
| Thermostat | Electronic, 50–85°F |
| Other | 12-hour auto-off timer, IR remote, caster wheels, 19 lb |
| Heat type | Infrared quartz |
| Maker’s coverage claim | None published — the coverage figure above is ours |
| Safety listing | No listing mark published in the listing text; check the cabinet's rating plate for the UL or ETL mark. |
Who it is for
A reader who wants to compute the load rather than trust a claim: the published amp draw and decibel figure make it the easiest unit on this site to check.
What it is not for
A 15 A circuit shared with anything else, and not a small room where a 19 lb cabinet on wheels is in the way.
Most plug-in heaters use 1,500 W on high and 750–900 W on low. Personal and desk heaters range from 200 to 800 W. Hardwired 240 V unit heaters run from 2,500 to 7,500 W.
Because a 120 V, 15 A branch circuit supports 12 A of continuous load, or 1,440 W. 1,500 W is the largest practical output a standard U.S. outlet can deliver, so it became the industry ceiling.
12.5 amps at 120 V — the arithmetic is 1,500 ÷ 120. That is above the 12 A continuous limit of a 15 A circuit, which is why it should not share a circuit with other significant loads.
For about 75 sq ft at average insulation — a small bedroom, a bathroom, a desk area. It is also a good holding setting for a 100 sq ft room once a 1,500 W unit has brought it up to temperature.
12.5 A against a 12 A continuous limit — the arithmetic nobody publishes, and what to do about it.
Cost per hour for any wattage at any rate — the calculator, the formula and the full grid.
Where the 10 W/sq ft rule comes from, when it breaks, and the exact watt-to-BTU conversion.
All electric heaters are 100% efficient. These are picked on the three things that actually cut the bill.
A correction, not a product pick: equal wattage means equal cost, and here is what actually varies.
Desk-side picks with a low setting, plus the circuit-load problem an office heater creates.