Off-grid, RV & cabin
Enter your load, panel, and battery. Find how many boondocking days you get between campground stops, and your shore power recharge time.
How it works
Step 1
This determines whether solar covers your daily use on its own while boondocking.
Step 2
Battery size sets how many deficit days you can absorb, and charger wattage sets recharge speed at the next stop.
Step 3
Know exactly how many boondocking days you can string together before needing a shore power stop.
For an 1,800Wh daily load against a 400-watt panel producing 1,600Wh a day, the battery loses 200Wh a day while boondocking. With 2,880Wh of usable capacity in a 300Ah 12V battery at 80% depth of discharge, that's about 14.4 days before the battery fully depletes, plenty of runway for most boondocking stretches between campground stops. Start with the DOE's overview of battery and energy storage technology if you need the official wording rather than a summary. Your inverter has to handle the biggest load you will run at once. The hybrid inverter sizing calculator in our Inverters & Equipment section can help you size it for your actual appliances.
Many RVers intentionally run a modest daily energy deficit while boondocking, since a mixed travel pattern means shore power at the next campground stop fully recharges the battery anyway. A negative daily balance only becomes a real concern if your typical boondocking stretch runs longer than the number of days your battery can absorb the deficit, which this tool tells you directly. A second sizing method is worth the check. The roof space vs output estimator in our System Sizing section can help you confirm the panel count from your daily load.
For a 2,880Wh usable battery capacity and a 600-watt shore power charger, a full recharge from empty takes about 4.8 hours, dramatically faster than solar alone could manage for the same battery capacity. This is exactly why a hybrid approach makes sense for many travelers: undersized solar for full boondocking coverage is fine when shore power reliably tops the battery back up between off-grid stretches. The battery charge time from grid calculator in our battery storage tools breaks this recharge math down further across different charger sizes.
If shore power covers the majority of your trip, sizing solar to fully cover only your longest realistic boondocking stretch, rather than indefinite off-grid use, usually saves money on panel capacity you'd rarely need at full output. Someone who boondocks 3 out of every 10 days needs a very different system than someone who boondocks continuously for weeks, even with identical daily loads. Battery cost and performance trends referenced throughout trace back to the National Laboratory of the Rockies Annual Technology Baseline.
Run the RV battery bank sizing calculator if your boondocking days feel too short for your actual travel pattern, and check the RV solar wattage calculator for a full panel sizing breakdown if you're building or upgrading your system from scratch. The battery lifespan estimator in our maintenance and lifespan tools is worth checking too, given how differently a battery ages under this kind of partial-deficit, shore-power-topped cycling versus a pure daily full-discharge pattern, and DOE's overview of battery and energy storage technology covers the fundamentals if any of this is new.
Questions
For an 1,800Wh daily load against a 400-watt panel producing 1,600Wh a day, the battery loses 200Wh a day while boondocking. With 2,880Wh of usable capacity in a 300Ah 12V battery at 80% depth of discharge, that's about 14.4 days before the battery fully depletes.
For a 2,880Wh usable battery capacity and a 600-watt shore power charger, a full recharge from empty takes about 4.8 hours, much faster than solar alone could manage for the same battery.
Not necessarily, if your boondocking stretches are shorter than the number of days your battery can sustain the deficit. Many RVers intentionally run a modest daily deficit while boondocking, since shore power at the next stop fully recharges the battery anyway.
Probably not. If shore power covers the majority of your trip, sizing solar to fully cover only your longest realistic boondocking stretch, rather than indefinite off-grid use, usually saves money on panels you'd rarely need at full capacity.