How Much Solar Do You Need for Van Life? (2026 Sizing Guide)
The amount of solar you need for van life comes down to one number: your daily energy use in watt-hours. Everything else — panel count, battery size, controller — follows from it. Most van builds land between 200 W and 800 W of solar, but the only way to know your number is to add up your loads and divide by your local sun. This guide walks through the whole chain, and the calculator does the arithmetic for you.
Step 1: Add up your daily watt-hours
For each appliance, multiply its watts by the hours you run it per day, then add everything together. A common setup looks like this:
- 12V fridge: 45 W × 10 h (compressor runtime) = 450 Wh
- Roof fan: 25 W × 8 h = 200 Wh
- Lights: 15 W × 4 h = 60 Wh
- Laptop: 65 W × 4 h = 260 Wh
- Phone charging: 10 W × 3 h = 30 Wh
That is 1,000 Wh a day. Note the fridge: it does not run constantly, so use its compressor runtime (roughly 8–12 hours in warm weather), not 24. This single step is where most sizing mistakes happen.
Step 2: Divide by peak sun hours
Peak sun hours (PSH) is the number of hours per day your location delivers full 1,000 W/m² sun. It ranges from about 6.5 in Arizona to under 1.5 in a Pacific Northwest winter. The solar formula adds a real-world derate:
array watts = daily Wh ÷ (peak sun hours × 0.75)
The 0.75 accounts for wiring resistance, controller inefficiency, heat, dust,
and imperfect panel angle. At 4 PSH our 1,000 Wh build needs
1000 ÷ (4 × 0.75) = 334 W — call it two 200 W panels or three
100 W panels. In an Arizona summer you might need only 250 W; in a UK winter,
well over 600 W for the same load.
Step 3: Match the battery to the panels
Solar fills the battery; the battery carries you through the night and cloudy
days. Size it from the same daily figure and the days of autonomy you want:
usable Wh = daily Wh × days ÷ depth of discharge. For our example
on LiFePO4 (0.8) over two days, that is
1000 × 2 ÷ 0.8 = 2,500 Wh, about 209 Ah at 12V. Panels and battery
are a pair — a big array with a small battery still leaves you dark by morning.
Step 4: Plan for winter and clouds
Annual-average sun hides the winter reality. If you travel in the cold months, size your array to winter PSH, not the yearly figure, or accept that you will lean on a DC-DC charger from the alternator and the occasional hookup. Cold also cuts usable LiFePO4 capacity by about 20%, and lithium must never be charged below 0 °C without a heater — plan for both.
Quick reference
- Weekender (fridge, fan, lights, phones): ~500–700 Wh/day → 200–300 W.
- Remote worker (add laptop, Starlink): ~1,000–1,500 Wh/day → 300–500 W.
- Full-timer with cooking: 2,000–3,000 Wh/day → 600–900 W.
These are starting points. Enter your own appliances in the calculator for exact watts, amp-hours, controller amperage, wire gauge, and an itemized cost range — then download the parts list.