The complete, plain-English guide. Work through it top to bottom and you will end with the battery, solar, inverter and charger sizes that match your actual lifestyle.
Every appliance you plug in consumes power measured in watt-hours (Wh) per day. Add up what you actually run:
A typical two-person van with a fridge, laptop work, lights and charging comes to roughly 1,200 to 2,000 Wh per day. Full-time power users running a heater, constant air-conditioning or Starlink can exceed 2,500 Wh per day.
Batteries are rated in amp-hours (Ah) at 12 volts. Convert your daily watt-hours to a battery size with a simple division, plus a buffer for cloudy days and depth of discharge:
Go LiFePO4 (lithium iron phosphate). It supports an 80 to 100% usable depth of discharge and thousands of charge cycles, which makes it the clear standard for van builds compared with older AGM lead-acid batteries.
Solar is your primary way to recharge off-grid. A good rule of thumb is 200 to 400 W of panel per 100 Ah of battery, though climate and roof space push this around. For full-time vanlife in a changeable climate with alternator charging available, 400 W of roof-mounted solar is a sensible starting point; plan for 600 W or more if you rely on solar alone in a cloudy region.
Use an MPPT (maximum power point tracking) charge controller rather than an older PWM type; it extracts noticeably more energy from the same panels. See our guide to solar sizing.
Inverter: converts DC battery power to standard AC for wall appliances. Pick the largest single draw you will run at once, then add headroom. A laptop and fridge are covered by 800 to 1,000 W; an induction hob or kettle needs 1,500 to 3,000 W.
DC-DC charger: charges your home battery from the alternator while you drive. 20 to 60 A is the practical range; match it to your battery size and alternator output. See our DC-DC guide.