Understanding your van life solar system
The direct answer for a typical van build
A van life build using 1,500Wh a day with 4.5 peak sun hours needs about 420 watts of panel and roughly 313Ah of 12V LFP battery at 80% depth of discharge for 2 days of autonomy, which rounds up to 400Ah, or four 100Ah batteries. This is a smaller system than most full-size RVs need, reflecting the generally lighter daily loads common in van conversions. Start with the NREL's PVWatts solar calculator if you need the official wording rather than a summary.
Why van roofs are the tighter constraint
Most cargo van roofs offer only 50 to 70 square feet of usable space once the roof fan, vents, and any rack mounting points are subtracted, compared to 150 or more square feet on a large travel trailer. At roughly 17 watts per square foot for rigid panels, that typically caps out around 850 to 1,200 watts, which comfortably covers most van life loads but leaves less headroom for future expansion than a larger rig would have. Current figures live on the DOE's solar photovoltaic technology basics, which updates them when the program changes.
Why weight and space favor lithium even more in a van
A van's interior space and payload are both tighter than a typical RV's, which makes LFP's advantages in weight and physical footprint over lead-acid even more valuable than in a larger build. Most modern van conversions default to LFP for this reason, on top of its higher usable depth of discharge, which shrinks the required battery bank size further for the same usable capacity.
Keeping the load realistic for a van
Van life loads commonly run 1,000 to 1,800Wh a day, noticeably lower than the 1,800 to 3,000Wh typical of larger RVs, mainly because vans tend to run smaller compressor fridges, fewer appliances, and less climate control equipment. Overestimating your load leads to an oversized, expensive system that may not fit the roof or the budget; the load list builder helps keep this number grounded in what you actually plan to run. A smaller van system may still qualify for the same federal tax treatment as a larger one, so it's worth checking the federal ITC calculator in our rebates and incentives tools. Remote systems are easy to neglect. The battery lifespan estimator in our Maintenance & Lifespan section can help you budget for the maintenance that keeps output from slipping.
What to check once you have a system size
Once you know your panel wattage and battery size, check the system weight and portability calculator for a full weight picture, and the charge controller sizing tool to match a controller to your specific array. The roof space vs output estimator in our system sizing tools is a useful second check given how tight van roof space typically runs, and production estimates throughout draw on NREL's PVWatts solar calculator. DOE's solar photovoltaic technology basics is a solid starting point if any of the fundamentals here need more background. Even off-grid, the money side matters. The payback period calculator in our Savings & Payback section can help you compare the system cost with the cost of extending the grid.