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The question has a short answer: watts of panel = watt-hours you use per day / peak sun hours, then a margin for losses. The long answer is that peak sun hours on a flat roof change by a factor of two to more than six between December and June in the states we read (Florida 2.2, Washington 6.4 [calc, NLR data]), so "how much" depends on when and where you camp.
Step 1: your daily watt-hours
From the power budget. As a reference, the published fridge figures run from 165 Wh a day (EcoFlow, fridge use) to 1,440 Wh (BougeRV's 60 W nonstop example).
Step 2: your peak sun hours
NLR's Solar Resource API gives the average daily solar energy on a flat surface, in kWh/m2/day, which equals peak sun hours. At the capital of each state we read, year average, December and June:
| State (capital) | Year average | December | June | 200 W panel, December [calc] | 200 W panel, June [calc] |
|---|---|---|---|---|---|
| Arizona (Phoenix) | 5.78 h | 3.18 h | 8.31 h | 636 Wh | 1,662 Wh |
| California (Sacramento) | 5.07 h | 1.84 h | 8.12 h | 368 Wh | 1,624 Wh |
| Colorado (Denver) | 4.83 h | 2.26 h | 7.21 h | 452 Wh | 1,442 Wh |
| Florida (Tallahassee) | 4.79 h | 2.8 h | 6.07 h | 560 Wh | 1,214 Wh |
| Nevada (Carson City) | 5.27 h | 2.11 h | 8.17 h | 422 Wh | 1,634 Wh |
| Oregon (Salem) | 3.77 h | 1.06 h | 6.13 h | 212 Wh | 1,226 Wh |
| Texas (Austin) | 4.74 h | 2.71 h | 6.63 h | 542 Wh | 1,326 Wh |
| Utah (Salt Lake City) | 4.71 h | 1.74 h | 7.49 h | 348 Wh | 1,498 Wh |
| Washington (Olympia) | 3.37 h | 0.88 h | 5.64 h | 176 Wh | 1,128 Wh |
How we compare: criteria, sources and dates
Source: NLR (formerly NREL) Solar Resource Data API v1, avg_ghi, read November 7, 2026. More states are added as the free API quota allows.
Step 3: divide, then add a margin
panel watts = daily Wh / peak sun hours / (1 - losses)
No maker in our list publishes one loss figure for a whole van system, so we leave the margin to you; the roof tool has a losses field. Then check that the panels fit: the tool tests the published size of each panel on your free roof area.
Panels in our check, by price per watt
| Panel | Watts | Size (published) | Area [calc] | Watts per sq ft [calc] | Price | Price per watt [calc] |
|---|---|---|---|---|---|---|
| Renogy 100W N-Type bifacial | 100 W | 34.1 x 22.8 in | 5.4 sq ft | 18.5 | $111.99 | $1.12 |
| Renogy 100W lightweight flexible | 100 W | 43.0 x 22.9 in | 6.8 sq ft | 14.6 | $149.99 | $1.50 |
| BougeRV Arch Pro 100W flexible | 100 W | 38.3 x 24.1 in | 6.4 sq ft | 15.6 | $159.99 | $1.60 |
| Renogy Flex ShadowFlux 100W | 100 W | 37.09 x 24.13 in | 6.2 sq ft | 16.1 | $172.99 | $1.73 |
| BougeRV N-Type 200W 16BB bifacial (12V) | 200 W | 51.57 x 30.2 in | 10.8 sq ft | 18.5 | $188.99 | $0.94 |
| BougeRV ShadePower 200W N-Type rigid | 200 W | 50.2 x 30.3 in | 10.6 sq ft | 18.9 | $195.99 | $0.98 |
| Renogy 200W N-Type bifacial | 200 W | 51.7 x 30.1 in | 10.8 sq ft | 18.5 | $199.99 | $1 |
| Renogy ShadowFlux 200W N-Type rigid | 200 W | 49.7 x 30.1 in | 10.4 sq ft | 19.3 | $239.99 | $1.20 |
| BougeRV Arch 2.0 200W flexible | 200 W | 53.0 x 30.9 in | 11.4 sq ft | 17.6 | $249.99 | $1.25 |
| BougeRV Arch Pro 200W ShadePower flexible | 200 W | 53 x 31 in | 11.4 sq ft | 17.5 | $269.99 | $1.35 |
| Renogy Flex ShadowFlux 200W | 200 W | 62.2 x 27.4 in | 11.8 sq ft | 16.9 | $299.99 | $1.50 |
| Renogy 200W flexible | 200 W | 63.2 x 29.4 in | 12.9 sq ft | 15.5 | $311.99 | $1.56 |
| BougeRV 300W N-Type 16BB bifacial | 300 W | 61.3 x 37.4 in | 15.9 sq ft | 18.8 | $369.99 | $1.23 |
| BougeRV Yuma 200W CIGS thin-film flexible | 200 W | 82.2 x 26.0 in | 14.8 sq ft | 13.5 | $439.99 | $2.20 |
| BougeRV 400W N-Type 16BB bifacial | 400 W | 67.8 x 44.6 in | 21.0 sq ft | 19.0 | $459.99 | $1.15 |
How we compare: criteria, sources and dates
Size as published. Area and watts per square foot [calc]. Prices read November 7, 2026.
When the roof is not enough
In a northern winter, few roofs can carry the watts the math asks for. The alternator is the usual second source: a DC-DC charger rated 30 A to 50 A puts back roughly 360 W to 600 W of charging while you drive [calc: amps x 12 V], whatever the weather.
Roof and wiring. Have panels, roof penetrations and the controller installed by a qualified installer, follow the manuals, and size the controller for the array (see the roof tool).
Frequently asked questions
How many solar panels for a camper van?
Divide your daily watt-hours by the peak sun hours where you travel, then by the panel watts. With a 1,000 Wh day in Phoenix over the year (5.78 h), you need about 173 W before losses [calc]: one 200 W panel. In Olympia in December (0.88 h) the same day would need about 1,136 W [calc], more than most van roofs hold.
How much solar for a 12V fridge?
Take the fridge's daily figure. EcoFlow publishes 165 Wh a day for its GLACIER Classic as a fridge: 165 / 5.78 = about 29 W of panel in Phoenix over the year, before losses [calc]. At the 60 W worst case (1,440 Wh), it is about 249 W [calc].
Is 400 watts of solar enough for van life?
It makes about 400 x peak sun hours a day before losses: 2,312 Wh over the year in Phoenix, 1,348 Wh in Olympia, but 352 Wh in Olympia in December [calc, NLR data]. Enough depends on your loads and on the season.