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, not a one-size-fits-all guess.
Every appliance you plug in consumes power measured in watt-hours (Wh) per day. Add up what you actually run. A simple way to start:
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 an electric heater, or 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 safety buffer for cloudy days and charge depth:
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.
Inverter: converts DC battery power to standard AC (mains) 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, topping it up on travel days and protecting the starter battery. 20 to 60 A is the practical range; match it to your battery size and alternator output.