Understanding your skoolie's power needs
The direct answer for a typical residential-style build
For a 3,500Wh daily load, common for a residential-style skoolie with a full-size fridge and a larger electronics setup, roughly 875 watts of solar covers the load at 5 peak sun hours. This is meaningfully more than a typical RV, reflecting the larger living space and heavier appliance choices common in bus conversions. The NREL's PVWatts solar calculator lays out the same rules from the regulator's side.
Why skoolie roofs rarely run out of space
A typical 35-foot bus roof offers around 216 square feet of usable area after obstructions like roof AC units and hatches and a reasonable edge clearance, enough for roughly 3,672 watts of panel capacity at standard density. This is far more than most conversions actually need, which is a real contrast to smaller RVs and vans where roof space is frequently the limiting factor rather than budget or load. Current figures live on the DOE's solar photovoltaic technology basics, which updates them when the program changes.
Why skoolie loads run heavier than a typical RV
Bus conversions frequently include residential-style appliances like a full-size fridge, an occasional-use washer, or a larger entertainment and electronics setup that a smaller RV typically doesn't carry, plus more square footage of lighting spread across a longer living space. This combination pushes daily load meaningfully above a typical RV's total, which is why sizing tools built for smaller rigs often undersize a bus conversion.
Choosing system voltage for a bus build
Many skoolie builders choose 24V or higher given the heavier loads and longer wire runs a bus conversion involves, since higher voltage reduces wiring losses and allows smaller-gauge, lighter, and less expensive wire for the same delivered power. A smaller, lighter-load conversion with shorter wire runs can still work well on 12V, so match voltage to your actual load and bus length rather than defaulting to whatever a smaller RV would use. The panel lifespan estimator in our maintenance and lifespan tools is worth running against whichever voltage and array size you land on.
What to check once you have a sizing result
Confirm your total daily load with the load list builder if you haven't already, and check battery voltage selection for a deeper look at choosing between 12V, 24V, and 48V for your specific build. Production estimates throughout draw on NREL's PVWatts solar calculator, and if your roof space estimate needs a second check, the maximum roof capacity calculator in our system sizing tools runs the same math from a slightly different angle. DOE's solar photovoltaic technology basics is a solid starting point if any of this is new territory.