Runtime = capacity × 85% ÷ (running watts × duty cycle). Solar energy = panel watts × 75% × peak sun hours. Appliance watts are typical planning values, not measurements.
Runtime from a battery
- 0.85 allows for inverter and conversion losses. Makers rarely publish this figure; real efficiency varies with load and temperature.
- Duty cycle is the share of time an appliance draws power: about 40% for a modern refrigerator, 100% for a router.
- Battery capacity ratings are the maker's; real usable capacity falls with cold, age and high discharge rates.
Starting watts
Assumes motors start one at a time. If a station states no surge rating we show "check surge" rather than assume one.
Solar recharge
| Region (approximate annual average) | Peak sun hours / day |
|---|---|
| Florida and the Gulf Coast | 5.2 |
| Texas | 5.0 |
| California | 5.5 |
| Southeast (GA, SC, NC) | 4.7 |
| Mid-Atlantic and Northeast | 4.2 |
| Midwest and Great Lakes | 4.2 |
| Mountain West | 5.4 |
| Pacific Northwest | 3.6 |
Generator fuel and cost
We never hard-code a fuel price; the calculators ask you for today's price.
Price per kWh and per watt
These are first screens: they ignore chemistry, weight, output limits and warranty.
What these numbers are not
They are not test results, not guarantees and not installation specifications. Appliance wattages are typical planning values; your appliances differ. Medical equipment, electrical connections and fuel storage need guidance from the device maker, a licensed electrician and local rules.
Figures marked as Wattstanding calculations show their working; product figures come from the sources on each product page. How we work