The site and the design
Roof area caps the panel array at about 400 W, mounted flat.
Phoenix's clearness index sits near 0.65 year-round, so the
small array pulls its weight every day; the bundled PVWatts TMY
data runs from 3.18 kWh/m²/day in December to 8.56 in June.
The battery is deliberately small too: a 100 Ah LiFePO4 bank at
12 V, which is plenty of energy but makes the peak-power
questions interesting.
- Solar array: 400 W, flat on the van roof
- Battery bank: 100 Ah LiFePO4 at 12 V (1,200 Wh)
- Charge controller: MPPT; inverter: pure sine wave, 90%
- Loads: 12 V compressor fridge, Maxxfan on summer
afternoons, LED lights, laptop and monitor, phone and camera
charging, and a 1,500 W induction burner for 15 minutes a
day; about 1,450 Wh/day total
Things to try
The induction burner is a 1,500 W spike on a 15-minute duty
cycle. Watch what happens to the inverter overload warning if
you bump it to a full hour. This example is built to show the
duty-cycle modeling: the
battery cares about average watt-hours, the inverter cares
about peak watts, and the two questions have different answers.
Open in calculator →
Frequently asked questions
How much solar do I need for a camper van?
Van roofs cap the array before your budget does; 400 W is a
realistic ceiling once a fan, vents, and roof rails claim their
space. This example runs a 12 V compressor fridge, a Maxxfan on
summer afternoons, LED lights, a laptop, device charging, and a
short induction-burner session (about 1,450 Wh per day) on
400 W in Phoenix. In a sunny climate that balances year-round;
the same build in the Pacific Northwest would need shore power
or a DC-DC charger in winter.
Can a van battery run an induction cooktop?
Briefly, yes. The burner in this example draws 1,500 W for
about 15 minutes a day, which is only about 375 Wh of energy,
easy for a 100 Ah LiFePO4 bank. The hard part is power, not
energy: the inverter must sustain 1,500 W plus its surge, and
the battery's BMS must allow the discharge current. That is why
this example pairs the small bank with a pure-sine inverter
sized for the spike, and why stretching the burner to a full
hour trips the calculator's overload warning.
What is a duty cycle and why does it matter for van appliances?
Duty cycle is the fraction of time an appliance is actually
drawing power. A compressor fridge with a 70 W nameplate might
run half the time, averaging 35 W, and the induction burner
here runs 15 minutes out of the hour you use it. The battery
sees the average; the inverter and wiring must handle the peak.
Confusing the two numbers is the most common van-build sizing
mistake, and it is the specific thing this example is built to
demonstrate.
More worked examples
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How the calculator works