Appliance Wattage Calculator
Add up running watts, daily watt-hours, and surge watts for the appliances you plan to power.
Results
Enter hours for at least one appliance, then compute.
How it works
Each appliance uses its running watts for the hours you run it. Add those up for daily watt-hours; add the watts themselves for the load if everything runs together.
daily_wh = Σ (running_w × hours)
running_w = Σ running_w
peak_w = running_w + max(surge_w − running_w)
running_w- Typical running watts of an appliance (from the DOE reference).
hours- Hours per day you run that appliance.
daily_wh- Sum of running watts × hours across all appliances.
running_w (total)- Sum of running watts if every selected appliance runs at once.
peak_w- Running total plus the single largest startup surge — what an inverter must survive.
Assumptions
- Running watts are representative values from the U.S. DOE appliance list; your model's nameplate may differ.
- Daily hours are editable estimates. The refrigerator default (8 h) follows DOE's guidance to divide plugged-in time by three for cycling.
- Surge watts are an engineering estimate — about 3× running for motor/compressor loads, 1× for resistive/electronic ones. Exact inrush varies by model.
- Running and peak watts assume every selected appliance runs at the same time (a conservative, worst-case load).
FAQ
How do I calculate an appliance's daily energy use?
Multiply its running watts by the hours you use it per day, then divide by 1000 for kilowatt-hours. A 725 W fridge running the equivalent of 8 hours uses about 5.8 kWh/day.
What is the difference between running watts and surge watts?
Running watts are the steady draw; surge (starting) watts are the brief spike when motors and compressors start — often two to three times higher. Inverters and generators must handle the surge.
Why assume everything runs at once?
Sizing to the worst case — all selected appliances on together — makes sure your inverter or power station never trips. Real homes rarely hit that peak, so you can trim if you know your usage.
Sources
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