Appliance Power Budget Calculator
Turns a list of appliances into the daily watt-hour figure every other sizing decision depends on, plus the inverter capacity they need.
| Appliance | Watts | Hours | Duty0 to 1 | Qty | Remove |
|---|---|---|---|---|---|
Daily energy use
1,940 Wh
1.94 kWh per day. This is the figure the system sizing calculator takes.
- Continuous base load
- 165 W
- Total if everything ran at once
- 220 W
- Minimum inverter surge capacity
- 670 W
Biggest consumers
- Refrigerator1,260 Wh (65%)
- Wifi router and modem360 Wh (19%)
- Laptop270 Wh (14%)
- LED light50 Wh (3%)
Why duty cycle matters more than anything else here
This is the single most common way an off-grid system gets oversized. A refrigerator rated 150 watts does not draw 150 watts for 24 hours. Its compressor cycles, running perhaps a third to a half of the time depending on ambient temperature and how often the door is opened.
Enter it as 24 hours at full draw and you overstate that one appliance by two or three times. Since every other component is sized from this total, the error then inflates the array, the battery bank, and the inverter. That is thousands of dollars of equipment bought to serve a number that was never real.
The presets fill in realistic duty cycles for the loads that cycle. Anything thermostatic belongs below 1: fridges, freezers, well pumps, and electric heating. Anything simply switched on stays at 1.
The three output figures
Daily energy use in watt-hours is what sizes your panels and your battery bank. It is the figure the system sizing calculator takes.
Continuous base load is what runs whether you are awake or not. On a small system this is often most of the overnight drain, and it is the first thing to attack if the budget comes out too high.
Minimum inverter surge capacity is the worst realistic instant: everything already running, and then the largest motor starts. Motors draw far more current starting than running, and an inverter that cannot supply that surge will not start the appliance at all. Only the largest single surge is added, because sizing for every motor starting simultaneously inflates the inverter well past what any real installation needs.
Where these wattages come from
The preset figures are typical values for planning, not measurements of your equipment. Real appliances vary considerably, and an old fridge can use several times what a current one does.
For anything that matters, measure it. A plug-in energy meter costs very little and will tell you what your fridge actually consumes across a day, including its duty cycle, which is worth far more than any estimate on this page.
Before sizing anything, it is worth reading off-grid solar basics, particularly the point that reducing consumption is almost always cheaper than generating more.