Published September 13, 2026 · Reserve Current editorial guide · Updated September 24, 2026
Quick answer: Budget energy per day: watts × hours for each device. Our example — a 10W light for 4 hours, a 30W laptop load for 3 hours and a 25W device running 24 hours — adds up to 730Wh, or about 859Wh from the battery at 85% efficiency, before idle draw and reserve.
Budget the day rather than the gadget list
Write down how long each device will run. A light used for two hours has a different impact from a cooler running through the day. Keep heating and cooking separate: short, high-power tasks can require an inverter that is much larger than the rest of your setup would suggest.
A transparent daily example
For illustration, a 10W light used for four hours consumes 40Wh. A 30W laptop load for three hours adds 90Wh. A device averaging 25W over 24 hours adds 600Wh. Together those loads consume 730Wh before conversion losses. Replace each example with a measurement or a realistic device-specific estimate.
Translate that to battery energy
At 85% conversion efficiency, 730Wh of AC energy requires about 859Wh from the battery before idle consumption. Holding 10% in reserve means nominal capacity must be larger again. Direct DC loads need their own conversion assumptions; mixing every port into one AC model can overstate or understate losses.
Plan the second day
A solar panel can replenish energy, but shade and weather can change the result considerably. Use the solar planner to compare a daily energy budget with a stated solar assumption. Keep a reduced-load plan for poor weather and follow the equipment’s temperature and moisture restrictions.
Frequently asked questions
How do I calculate a camping power budget?
Multiply each device's watts by the hours it runs, then add them up. A 10W light for 4 hours is 40Wh; a 30W laptop load for 3 hours is 90Wh; a device averaging 25W for 24 hours is 600Wh. Together: 730Wh.
How big a battery do I need for 730Wh a day?
At 85% conversion efficiency, 730Wh of AC energy needs about 859Wh from the battery before idle consumption. Holding 10% in reserve means the nominal capacity must be larger again.
Can solar cover the second day?
It can help, but shade and weather change the result considerably. Compare your daily budget with a stated solar assumption and keep a reduced-load plan for poor weather.