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BTU to Watts Chart: Quick Reference Tables
Conversion tables for the values you actually shop for — room AC sizing, heat pumps, gas appliances, and more.
Why a chart beats a formula
A chart beats a formula when you’re standing in an appliance aisle or sketching a heat load on the back of a receipt. This page collects the conversions most people need: small appliances, room AC units, central systems, and large commercial gear.
Every value uses the standard factor of 3.412 BTU/h per watt (or 0.293 W per BTU/h). Numbers are rounded to a sensible precision for shopping and sizing.
The master chart
| BTU/h | Watts | Kilowatts | Typical Use |
|---|---|---|---|
| 500 | 147 | 0.15 | electric blanket |
| 1,000 | 293 | 0.29 | small fan heater |
| 2,000 | 586 | 0.59 | desk-side heater |
| 3,000 | 879 | 0.88 | mini space heater |
| 4,000 | 1,172 | 1.17 | small room heater |
| 5,000 | 1,466 | 1.47 | bedroom AC, 150 sq ft |
| 6,000 | 1,759 | 1.76 | small office AC |
| 7,000 | 2,052 | 2.05 | medium room AC, 250 sq ft |
| 8,000 | 2,345 | 2.35 | mid-size window AC |
| 9,000 | 2,638 | 2.64 | mini-split, 350 sq ft |
| 10,000 | 2,931 | 2.93 | living room AC |
| 12,000 | 3,517 | 3.52 | 1-ton AC, 500 sq ft |
| 14,000 | 4,103 | 4.10 | portable AC |
| 15,000 | 4,396 | 4.40 | large window AC |
| 18,000 | 5,275 | 5.28 | 1.5-ton mini-split |
| 20,000 | 5,861 | 5.86 | small ductless system |
| 24,000 | 7,034 | 7.03 | 2-ton AC, 1,000 sq ft |
| 30,000 | 8,793 | 8.79 | 2.5-ton system |
| 36,000 | 10,551 | 10.55 | 3-ton AC, 1,500 sq ft |
| 42,000 | 12,310 | 12.31 | 3.5-ton system |
| 48,000 | 14,068 | 14.07 | 4-ton AC, 2,000 sq ft |
| 60,000 | 17,585 | 17.59 | 5-ton AC, 2,500 sq ft |
| 72,000 | 21,102 | 21.10 | 6-ton commercial |
| 96,000 | 28,136 | 28.14 | 8-ton commercial |
| 120,000 | 35,170 | 35.17 | 10-ton commercial |
The sq ft ratings are rough guides for a moderately insulated home in a temperate US climate. Hot climates, poor insulation, or south-facing rooms push the BTU requirement up by 10–30%.
Watts to BTU/h (reverse direction)
| Watts | BTU/h | Typical Device |
|---|---|---|
| 60 | 205 | LED lighting cluster |
| 100 | 341 | incandescent bulb |
| 200 | 682 | desktop monitor |
| 300 | 1,024 | gaming console |
| 500 | 1,706 | desktop computer |
| 750 | 2,559 | small space heater |
| 1,000 | 3,412 | toaster, kettle |
| 1,200 | 4,094 | hair dryer |
| 1,500 | 5,118 | full-size space heater |
| 1,800 | 6,142 | 15 A outlet limit |
| 2,400 | 8,189 | electric kettle (UK) |
| 3,000 | 10,236 | clothes dryer (partial) |
| 5,000 | 17,060 | electric furnace (small) |
| 7,500 | 25,590 | mid heat pump |
| 10,000 | 34,120 | electric furnace |
| 15,000 | 51,180 | EV charger (level 2) |
| 20,000 | 68,240 | whole-house heat |
Air conditioner sizing chart
Match room size to BTU/h, then read across for the metric equivalent.
| Room Size (sq ft) | BTU/h | Watts |
|---|---|---|
| 100–150 | 5,000 | 1,466 |
| 150–250 | 6,000 | 1,759 |
| 250–300 | 7,000 | 2,052 |
| 300–350 | 8,000 | 2,345 |
| 350–400 | 9,000 | 2,638 |
| 400–450 | 10,000 | 2,931 |
| 450–550 | 12,000 | 3,517 |
| 550–700 | 14,000 | 4,103 |
| 700–1,000 | 18,000 | 5,275 |
| 1,000–1,200 | 21,000 | 6,155 |
| 1,200–1,400 | 23,000 | 6,742 |
| 1,400–1,500 | 24,000 | 7,034 |
| 1,500–2,000 | 30,000 | 8,793 |
| 2,000–2,500 | 34,000 | 9,964 |
Adjustments:
- Kitchen: add 4,000 BTU/h
- Heavy sun exposure: add 10%
- Heavy shade: subtract 10%
- Per occupant over two: add 600 BTU/h
- High ceilings (above 8 ft): add 10–15%
Heat pump and tonnage chart
HVAC tonnage is an old refrigeration unit. One ton equals 12,000 BTU/h.
| Tons | BTU/h | Watts | Coverage |
|---|---|---|---|
| 0.5 | 6,000 | 1,759 | small bedroom |
| 0.75 | 9,000 | 2,638 | studio apartment |
| 1.0 | 12,000 | 3,517 | one-bedroom |
| 1.5 | 18,000 | 5,275 | two-bedroom condo |
| 2.0 | 24,000 | 7,034 | small house |
| 2.5 | 30,000 | 8,793 | 1,500 sq ft home |
| 3.0 | 36,000 | 10,551 | 1,800 sq ft home |
| 3.5 | 42,000 | 12,310 | 2,200 sq ft home |
| 4.0 | 48,000 | 14,068 | 2,500 sq ft home |
| 5.0 | 60,000 | 17,585 | 3,000 sq ft home |
The watt column shows thermal capacity, not electrical draw. A 3-ton heat pump pulling 3,000 W from the wall outputs 10,551 W of heating or cooling — the difference comes from moving heat instead of generating it.
Gas appliance conversions
Gas appliances list input ratings in BTU/h. The converted watt figure shows the equivalent electrical heating power.
| Appliance | BTU/h | Watt Equivalent |
|---|---|---|
| pilot light | 600 | 176 |
| gas stove burner (small) | 7,000 | 2,052 |
| gas stove burner (large) | 12,000 | 3,517 |
| gas oven | 18,000 | 5,275 |
| tankless water heater (small) | 140,000 | 41,032 |
| tankless water heater (large) | 199,000 | 58,323 |
| gas furnace (small) | 60,000 | 17,585 |
| gas furnace (medium) | 80,000 | 23,447 |
| gas furnace (large) | 100,000 | 29,309 |
| gas furnace (whole-house) | 120,000 | 35,170 |
Note the gap: a small tankless water heater equals 41 kW of electrical power. Switching from gas to electric for hot water often requires a panel upgrade.
Boilers and industrial equipment
| Equipment | BTU/h | kW |
|---|---|---|
| residential boiler (small) | 50,000 | 14.7 |
| residential boiler (medium) | 100,000 | 29.3 |
| residential boiler (large) | 200,000 | 58.6 |
| light commercial boiler | 500,000 | 146.5 |
| commercial boiler | 1,000,000 | 293.1 |
| industrial boiler | 5,000,000 | 1,465.4 |
At industrial scale, BTU figures pass into the millions, and the metric equivalent crosses into megawatts.
Solar and off-grid sizing
Running AC on solar power means converting BTU/h to actual electrical draw, not just thermal capacity. The ratio is the EER.
| AC Size | EER | Running Watts | Solar Panels (300 W each) |
|---|---|---|---|
| 5,000 BTU/h | 11 | 455 | 2 |
| 8,000 BTU/h | 11 | 727 | 3 |
| 10,000 BTU/h | 11 | 909 | 4 |
| 12,000 BTU/h | 12 | 1,000 | 4 |
| 18,000 BTU/h | 12 | 1,500 | 6 |
| 24,000 BTU/h | 12 | 2,000 | 7 |
The running watts assume the AC is at full load. Variable-speed inverter units use less on average. Panel counts assume 4 hours of peak solar production and lossless inverters — real installations need 30–50% more.
Conversion constants
Keep these for any value not on the charts:
- 1 W = 3.412 BTU/h
- 1 BTU/h = 0.293 W
- 1 kW = 3,412 BTU/h
- 1 ton (refrigeration) = 12,000 BTU/h = 3.517 kW
- 1 hp (horsepower) = 2,545 BTU/h = 746 W
For exact values, use the BTU/hr to kW, BTU/hr to tons, BTU/hr to horsepower, or BTU/hr to kcal/hr calculators.
How to read these charts
Pick the row that matches your known value. The row tells you the other unit, the typical use case, and a rough size category. The numbers are tools, not promises — every building, climate, and appliance has its quirks. Use the chart for a starting point, then check the nameplate on the actual gear before you buy.