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Power Strip Overload Calculator
Add up what is plugged into your power strip and compare it with the strip’s rating. Set for 120 V US outlets, with other voltages available.
Check your power strip
Capacity at 120 V
| Rating | Capacity | 80% line |
|---|---|---|
| 15 A | 1,800 W | 1,440 W |
| 13 A | 1,560 W | 1,248 W |
| 10 A | 1,200 W | 960 W |
A 1,500 W space heater alone uses 83% of a 15 A strip, and it should not be on a strip at all.
How the check works
Capacity is the strip’s amp rating times the outlet voltage. The appliances you pick are added up and compared with it: above 80% is “Caution” and above 100% is “Overloaded”. Space heaters, heat-producing appliances and major appliances are flagged even when the total is low, because U.S. fire safety guidance says to plug them directly into a wall outlet.
Safe use
- Use power strips with internal overload protection.
- Do not run cords under rugs or carpets, where they can be damaged.
- Replace worn or damaged cords right away.
Frequently asked questions
How many watts can a power strip handle?
Multiply its amp rating by the voltage. A 15 A strip on a 120 V US outlet handles 1,800 W in total, across all of its outlets together.
Can I plug a space heater into a power strip?
No. The U.S. Fire Administration says to plug space heaters directly into a wall outlet and never into an extension cord or power strip.
Why does the calculator warn at 80%?
Appliances can draw more than their label for a moment, for example when a motor starts. Staying under 80% of the rating leaves a margin. This threshold is our own rule of thumb.
More tools
Sources and last updated
- Major appliances, overloads and cords: U.S. Fire Administration, Appliance and Electrical Fire Safety
- Space heaters: U.S. Fire Administration, Space Heater Safety Tips
- Heat-producing appliances: U.S. Fire Administration, Electrical Fire Safety infographic (PDF)
- Appliance wattages (high end of nameplate ranges): Virginia Cooperative Extension, Estimating Appliance and Home Electronic Energy Use (BSE-301, PDF)
- The 80% caution line is our own rule of thumb.
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