Campervan Power Basics (Explained Simply)
Understand volts, amps, and watts in minutes. Use the Power Triangle to size your system without guesswork.
What the numbers mean
Volts (V) — pressure. Most van systems are 12V.
Amps (A) — flow. How fast electricity moves.
Watts (W) — power. What your appliances actually use.
The Power Triangle: Watts = Volts × Amps. Rearranged: Amps = Watts ÷ Volts, Volts = Watts ÷ Amps.
Example: A 120W fridge on 12V draws about 10A while running (120 ÷ 12 = 10A).
Step 1 — List your appliances
Write down each item, its watts, and hours per day. Fridge, lights, water pump, laptop, heater fan, etc.
Step 2 — Work out daily usage
For each item: watt-hours = watts × hours. Add them up for your daily total.
Step 3 — Convert to battery size
Battery capacity is in amp-hours (Ah). Convert your daily watt‑hours to Ah by dividing by 12:
Ah per day ≈ watt‑hours ÷ 12
Add a buffer (1.5–2×) so you’re covered for cloudy days and inverter losses.
Skip the maths? Use our spreadsheet to size batteries, inverter, and solar in minutes.
What about solar and charging?
Solar tops you up when parked. Alternator charging covers drive days. Shore power is optional for campsites.
Pick sizes after you know your battery target — not before.
Safety basics
Protect every positive cable with a fuse or breaker sized to the cable. Keep cable runs short. Use correct lugs and tighten properly.
All electrical work should be checked or carried out by a qualified professional.
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