20 Amps to Watts
20 A is 4,600 W at 230 V and 2,400 W at 120 V (single-phase, power factor 1). Table for DC and three-phase, power factor 0.8, and the formula.
Formula
Worked example
- P = 230 × 20 × 1 = 4,600 W
- With a power factor of 0.9: P = 230 × 20 × 0.9 = 4,140 W
On other supplies
| Supply | Voltage | Power at pf 1 | Power at pf 0.8 |
|---|---|---|---|
| DC | 12 V | 240 W | not used |
| DC | 24 V | 480 W | not used |
| DC | 48 V | 960 W | not used |
| Single-phase | 120 V | 2,400 W | 1,920 W |
| Single-phase | 230 V | 4,600 W | 3,680 W |
| Single-phase | 240 V | 4,800 W | 3,840 W |
| Three-phase | 208 V | 7,205 W | 5,764 W |
| Three-phase | 400 V | 13,860 W | 11,090 W |
| Three-phase | 415 V | 14,380 W | 11,500 W |
| Three-phase | 480 V | 16,630 W | 13,300 W |
Three-phase rows use the line-to-line voltage. DC ignores the power factor.
What 20 A looks like
20 A is a common branch circuit rating for kitchens and workshops in North America, at 120 V.
This is an estimate of the load current only. Choosing a cable or a breaker also needs the installation method, the ambient temperature, the voltage drop and the rules you work to.
Frequently asked questions
How many watts is 20 amps?
20 A is 4,600 W on a 230 V single-phase supply and 2,400 W on 120 V, both with a power factor of 1. The power depends on the voltage, so it is a different answer on every supply.
What if the power factor is not 1?
The real power falls. At 230 V and a power factor of 0.9, 20 A is 4,140 W. Heaters and filament lamps are close to 1, while motors and many power supplies are lower.
What about a three-phase supply?
20 A on 400 V three-phase at a power factor of 0.8 is 11,090 W. The line voltage is used with the factor √3 (about 1.732).
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