How Many Watts of Solar Does an RV Need for 720 Wh a Day?
Summary
If the goal is only to replace each day's use, Victron Energy's worked example lands at 144 W. Victron itself calls that not ideal for an RV that rarely moves and leans on solar, and recommends a bigger array of 450 to 500 W so the batteries can refill in 4 to 5 peak sun hours. That is about triple the minimum.
The example load
Victron's May 2026 sizing guide adds up three loads: laptop charging at 60 W for 3 hours (180 Wh), a 12 V, 70-liter fridge (500 Wh), and lights at 10 W for 4 hours (40 Wh), for 720 Wh a day. It adds that AC appliances such as the laptop charger need about 10 to 15% extra in practice.
On a 12 V system, 720 Wh is about 60 Ah a day. Three days without charging means 180 Ah. Victron treats about 90% of a lithium battery and about 50% of a lead-acid battery as usable, which gives roughly 200 Ah of lithium or 360 Ah of lead-acid.
From 144 W to 500 W
Victron defines peak sun hours as the equivalent hours per day at 1,000 W per square meter of sunlight, and uses an Alpine village in summer, at around 5 hours, as its example. Dividing 720 Wh by 5 hours gives the 144 W figure.
A 144 W array covers daily use, but after three days of drawing down, refilling the bank would take 3 to 4 consecutive sunny days. Victron's practical target is a full recharge from solar alone in 4 to 5 peak sun hours, so the battery recovers in a single sunny day. Hitting that means roughly tripling the array to around 450 to 500 W. As the guide puts it, arrays are often sized well beyond the daily-consumption minimum, especially for RVs that spend long stretches off-grid.
A tension between two Victron guides
Victron's September 2026 guide to RV components recommends not regularly discharging lithium below 20%. Plan on 80% usable capacity in place of 90% and the same 180 Ah requirement becomes about 225 Ah of battery, a bit over 10% more than the 200 Ah in the sizing example, with correspondingly more energy to put back.
For the charge controller, the sizing guide names three panel figures: watts, open-circuit voltage, and short-circuit current. Series wiring raises voltage and parallel wiring raises current, so the controller has to match the combined Voc for a series string, the combined Isc for parallel panels, and the battery voltage of 12, 24, or 48 V. The SmartSolar MPPT 100/30 in Victron's example accepts up to 100 V from the array and delivers up to 30 A to the battery.
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Sources
- Victron Energy — How to Size a Solar System for Your RV (May 4, 2026)
- Victron Energy — Understanding the Components of Your RV Electrical System (September 3, 2026)
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