Sized picks · 300 sq ft
This is where a single plug-in heater stops being a solution and becomes a supplement. 300 square feet wants 3,000 watts; an outlet gives you half.
How this page is funded: we earn a commission if you buy through the links here, at no extra cost to you. Picks are chosen before links are attached, which is why every roundup names something to skip. Full disclosure.
A 300 sq ft room needs about 3,000 W at average insulation and an 8-foot ceiling. One plug-in heater delivers 1,500 W — exactly half. A single unit will not hold this room on its own in cold weather; it will run continuously and take the edge off.
300 sq ft × 10 W = 3,000 W. One heater is 1,500 W. The shortfall is 50% — the largest of any room size on this site where people still expect a single heater to work.
| Room size | Watts needed | BTU/h | Plug-in heaters |
|---|---|---|---|
| 200 sq ft | 2,000 W | 6,824 | 2 (different circuits) |
| 300 sq ft | 3,000 W | 10,236 | 2 (different circuits) |
Computed as square feet x 10 W x insulation factor x (ceiling / 8 ft), for an average heated room — 10 W/sq ft, 8 ft ceiling. Heater count assumes the 1,500 W plug-in ceiling.
A 300 sq ft room is a large living room, a primary bedroom, a finished basement room or a studio apartment's main space: roughly 15 × 20 feet. It is also, not coincidentally, the coverage figure several manufacturers print on 1,500 W heaters — which is where this page earns its keep.
Two 1,500 W units give you the 3,000 W the room actually wants. The constraint is electrical, not financial: two heaters draw 25 A between them, and no residential 15 or 20 A circuit will carry that. They must be on genuinely separate circuits, which in an older home or an apartment is less common than people assume — one circuit often serves several rooms.
Check the panel before buying the second heater, not after. How to work out what shares a circuit.
If the room is large because it is open-plan but you occupy one end of it, radiant heat aimed at where you sit delivers comfort without trying to raise the air temperature of 300 square feet. This is the same reasoning that makes infrared the right answer in a garage, applied to a room that is merely large rather than uninsulated. The trade-off is that it warms what it can see. Convection vs radiant.
The most common realistic use at this size: the central system does the bulk and the space heater closes a gap in one cold room, so the thermostat for the whole house does not have to be raised. That is a legitimate and often economical strategy — and whether it saves money depends entirely on your fuel. Space heater vs central heat, worked through.
One 1,500 W heater in a 300 sq ft room will make it noticeably more comfortable and will not make it warm on the coldest nights. That is a fine outcome if it is what you expected. It is a bad outcome if a box promised you 300 sq ft.
| Wattage | Per hour | 1 h | 8 h |
|---|---|---|---|
| 1,500 W | 27.5¢ | $0.28 | $2.20 |
| 3,000 W | 55.0¢ | $0.55 | $4.40 |
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. Figures assume full output for the whole period.
A single heater is 27.5 cents an hour; two are 55 cents. The figure people miss is that in an under-sized room the heater never cycles off — it never reaches the set point, so there is no duty-cycle discount. Where a correctly sized heater in a 100 sq ft room might run 60% of the time, one in a 300 sq ft room runs 100% of it. Budget the full-output number for every hour it is on.
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.
| Heater | Draw at 120 V | 15 A circuit (12 A limit) | 20 A circuit (16 A limit) |
|---|---|---|---|
| 1,500 W | 12.5 A | Over the limit | Fits |
| 3,000 W | 25.0 A | Over the limit | Over the limit |
| Maximum continuous | — | 12 A = 1,440 W | 16 A = 1,920 W |
Draw computed as watts / 120 V. The continuous limit is 80% of the breaker rating, which follows from the NEC's requirement to size a circuit at 125% of a continuous load (NFPA 70, 210.19(A)(1) and 210.20(A)).
One heater at 12.5 A is already over the 12 A continuous allowance of a 15 A circuit. Two at 25 A is beyond any residential circuit. If the plan is two heaters, the plan is also two circuits — and confirming that is a five-minute job with the breaker panel and a lamp. The continuous-load rule.
Picked for a room a single heater cannot hold: the largest honest convection output, a unit built to run continuously without complaint, a radiant option for heating people instead, and a silent radiator for a 300 sq ft bedroom.
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 |  Dreo Solaris 718The rare heater whose published coverage claim survives the arithmetic: 1,500 W is a genuine 300 sq ft at 10 W/sq ft, and Dreo publishes that number rather than implying more. | A whole living room | 150 sq ft | 12.5 A | $129.99 · Check on Amazon |
| 2 |  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 | $138.65 · Check on Amazon |
| 3 |  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 | $112.99 · Check on Amazon−10% |
| 4 |  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 |
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 · A whole living room
The rare heater whose published coverage claim survives the arithmetic: 1,500 W is a genuine 300 sq ft at 10 W/sq ft, and Dreo publishes that number rather than implying more.
| Published specification | |
|---|---|
| Rated power | 1,500 W at 120 V |
| Maker's coverage claim | 300 sq ft |
| Thermostat | 41–95°F digital, 1°F increments |
| Oscillation | 30° / 60° / 90° / 120° |
| Dimensions | 7.9" D x 7.9" W x 29.7" H, 8 lb |
| Safety | Tip-over cutoff, overheat cutoff, child lock, thermal cutoff |
| Heat type | Ceramic (PTC) |
| Maker’s coverage claim | 300 sq ft |
| Safety listing | ETL listed (stated by Dreo on the product page) |
Who it is for
A living room, bedroom or den at or under 300 sq ft with average insulation and an 8-foot ceiling, where you want to set a temperature and stop thinking about it.
What it is not for
A garage, an uninsulated basement, or anything over about 300 sq ft. It is not under-powered — 1,500 W is the plug-in ceiling — the room is simply too big for one outlet.
2 · 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
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.
4 · 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
And what we did not do: we have not tested these units, owned them, measured them or run them in a room. Everything above is compiled from published manufacturer specifications and live retail listings, with the electrical load, room coverage and running cost computed by us from the published wattage. The full method.
About 3,000 W at 10 watts per square foot with average insulation and an 8-foot ceiling. One plug-in heater supplies 1,500 W, so a single unit covers half the demand — the options are two heaters on two circuits, radiant heat aimed at people, or using it as a supplement to central heating.
Not on its own in cold weather. It supplies half the 3,000 W the room needs at the standard rule, so it will run continuously without reaching a set point and will take the edge off rather than making the room warm. Several heaters are nonetheless sold with a 300 sq ft claim on the box.
Yes, but they must be on different circuits. Two 1,500 W heaters draw 25 A between them, well beyond any residential 15 or 20 A circuit. In older homes and apartments a single circuit often serves several rooms, so check the panel before buying the second one.
About 27.5 cents an hour for one 1,500 W heater, or 55 cents for two, at the U.S. average rate. Budget the full figure for every hour — in an under-sized room the heater never reaches its set point, so it never cycles off and there is no duty-cycle saving.
A 15 × 20 room is 300 square feet and needs about 3,000 W. That is twice what one plug-in heater delivers, so plan for two units on separate circuits, radiant heat for the occupied end, or supplementary use alongside central heating.
200 sq ft wants 2,000 W and an outlet gives 1,500. The gap, and four ways to close it.
5,000 W of demand against 1,500 W of supply — what actually works in a studio or open-plan space.
The four units that get closest to a 300 sq ft room — and the two-heater arithmetic nobody publishes.
Room dimensions in, wattage and BTU out — with both corrections applied and the formula visible.
12.5 A against a 12 A continuous limit — the arithmetic nobody publishes, and what to do about it.
Per-BTU arithmetic for gas, oil and electric — and the one condition that decides the answer.