Start with watt-hours per day
List lighting, refrigeration, communications and other equipment. For continuous loads, multiply average watts by 24 hours. For intermittent equipment, use realistic hours of operation. Keep output and motor-starting checks separate from the energy budget.
A 60W average combined load uses 1,440Wh each day. At an assumed 85% delivery efficiency, it takes about 1,694Wh from nominal battery energy before adding a reserve.
Choose a cloudy-day reserve
If your plan requires two days without useful charging, the storage requirement doubles before reserve. A portable system can become heavy and expensive at this point. Compare it with a properly designed fixed battery installation if you need continuous, long-term off-grid power.
Expansion packs extend energy storage only when the manufacturer supports that exact combination. They generally do not raise inverter output.
Balance solar production
At an illustrative four peak-sun-hours and 75% overall yield, 600W of panels produces around 1,800Wh in a day. That barely covers the example load after losses and leaves little for recovery. Seasonal and site-specific sunlight matter.
Check input voltage and current as well as watts. Do not design a series string near the station’s maximum voltage without accounting for the panels’ higher open-circuit voltage in cold conditions.
Have a recovery plan
After a cloudy period, you need additional generation or reduced consumption to refill storage while powering normal loads. A “one-day recharge” calculation that ignores simultaneous loads can be misleading.
Decide ahead of time which loads can be deferred. Keep essential communication and safe lighting ahead of discretionary cooking or heating loads.