How Much Solar Do I Need for My RV?
Estimate your daily usage in watt-hours, then divide by realistic sun-hours — 3 to 5 depending on season and region. As a rule of thumb, 1,000 Wh/day of usage needs roughly 300–400W of panels.
Roof space is usually the real limit on vans and smaller RVs. That is where high-efficiency panels and alternator charging make up the difference.
You're probably here because…
- Panel listings are all watts, and nobody explains how many watts you need.
- You have limited roof space and want to know whether solar alone can cover it.
- You keep reading that solar is not enough on its own and want a straight answer.
How do I work out my daily usage?
List each load, its watts, and its hours per day, then multiply and add. A 12V fridge running a realistic compressor duty cycle, LED lighting, laptop and phone charging, plus pumps and fans, commonly lands near 1,000 Wh/day for daily off-grid use. Your own numbers will differ — and that difference is the entire point of sizing.
How do watt-hours become panel watts?
Divide daily watt-hours by realistic sun-hours for your season and region. Sun-hours are not daylight hours: 3 to 5 is the honest working range for most of the year in most of the US. At 1,000 Wh/day and 3 sun-hours you need roughly 330W of panels; the same usage at 5 sun-hours needs about 200W. Sizing to the pessimistic end is what keeps the bank full in shoulder seasons.
What does that look like per kit level?
Starter — Weekend Ready
≈100W
Weekend and light use
Mid-Level — Road Life
≈175W
Regular travel, remote work
Advanced — Full-Time Freedom
2 × ≈175W (≈350W)
Full-time living, heavy use
Component sizing follows APS engineering revision v0.2, approved by APS engineering. Final panel models are being confirmed with our solar vendor.
What if the roof will not fit enough panels?
This is the normal outcome on vans, and it is not a problem — it just means solar is not your only charging source. A DC-DC charger takes power from the alternator while you drive, which is the cheapest reliable charging you can add. Solar keeps the bank topped up while parked; the alternator does the heavy lifting on travel days. Most owners who feel short on solar are actually short on charging strategy.
Building it yourself?
The five failures we see most in DIY camper and van electrical builds — all of them decisions made early.
Frequently asked questions
Only up to what your controller and bank can absorb. Panels beyond that point are money spent on a system that cannot use them — sizing the controller and bank alongside the array is what makes the extra watts count.
Output drops sharply, which is why days of autonomy and a second charging source matter more than a bigger array. In winter, shorter solar days raise the autonomy you need, and lithium batteries need low-temperature charge protection — check that your battery or BMS includes it.
Yes for anything beyond a trickle panel. An MPPT controller harvests meaningfully more from the same panels than a PWM controller, and it has to be sized to the array after the final panel selection.
Skip the arithmetic
The APS Power Guide asks about your actual loads, how long you stay out, and how you recharge — then recommends a right-sized system instead of a panel count.