Van Inverters & 120V Power (US Guide): Sizing & Safety 2026

· 4 min read

An inverter turns your 12V battery power into the 120V AC your household appliances expect. It's what lets you run a laptop charger, blender, or microwave off-grid. But inverters also pull enormous current from your battery, so sizing and wiring them correctly matters. This guide covers what to buy, how big, and how to wire it safely.

For how the inverter fits the whole system, see the complete electrical system guide.

Size your inverter to your loads

Tell us your 120V appliances and we'll size the inverter and its cabling — free.

Get my free design

Do you even need one?

Plenty of efficient van builds skip the inverter entirely. Phones, tablets and most laptops charge over 12V/USB directly, which is more efficient than going 12V → 120V → charger. You only need an inverter if you'll run genuinely AC-only appliances: a microwave, induction cooktop, full-size blender, power tools, or some CPAP setups.

If your AC needs are occasional and small, a portable power station can be simpler than a hardwired inverter — see power station vs. house battery.

Pure sine, always

Buy a pure sine wave inverter, not modified sine. Pure sine produces clean power that's safe for electronics, motors, and chargers. Modified sine can buzz, run motors hot, and damage sensitive gear — the small savings aren't worth it.

Sizing

Size the inverter about 25% above your largest simultaneous 120V load:

  • Laptop + phone chargers: 300–800W is plenty.
  • Microwave (~1,000W draw) or blender: 1,000–1,500W.
  • Induction cooktop (1,500–1,800W): 2,000W+ — and a big battery to feed it.

Remember the battery side: a 2,000W inverter at full load pulls roughly 2,000W ÷ (12V × 0.87) ≈ 190A from the battery. That demands very heavy cable (2/0 AWG) and a large bank.

US picks: Victron Phoenix 12/800 ($250) for light use, Renogy 1000W pure sine ($150) mid-range, Victron MultiPlus 12/2000 (~$900) if you want a combined inverter/charger.

Watch standby draw

Inverters consume power just being on. Add a remote switch and turn the inverter off when you're not using AC, or it'll quietly drain your battery overnight.

Wiring and fusing

The inverter's supply cable is the heaviest in the van and carries the most current, so it gets special care:

  • Size the cable in AWG for the inverter's full-load current (often 2/0 AWG for a 2,000W unit).
  • Fuse it with an ANL or Class T fuse at the bus bar end, sized to the inverter's draw and the cable's rating.
  • Keep the run as short as possible and use crimped lugs.
  • Prefer the cable and fuse sizes from the inverter's manual where they differ from a general rule.

See the wiring & safety guide for the full method.

120V output is real household power

The inverter's 120V output is as dangerous as a wall outlet. Fixed 120V wiring, outlets, and any tie-in with shore power must follow NEC Article 551 and GFCI requirements — install or have it inspected by a licensed electrician. Never back-feed an inverter into your shore inlet without a proper transfer switch.

Inverter/charger combo

If you'll run both an inverter and shore power, an inverter/charger (like the Victron MultiPlus) combines both jobs in one box, with an automatic transfer switch that uses shore power when it's plugged in and the inverter when it isn't. It's tidier and avoids wiring conflicts — covered alongside shore power in the charging systems guide.

FAQ

What size inverter do I need for a van?

Size it about 25% above your largest simultaneous 120V load. 300–800W covers laptop and phone charging; 1,000–1,500W runs a microwave; 2,000W+ is needed for an induction cooktop (plus a large battery). Use the calculator to size it and its cabling.

Do I need an inverter in my van?

Only if you run AC-only appliances like a microwave, induction cooktop, or power tools. Phones and most laptops charge over 12V/USB more efficiently, so many efficient builds skip the inverter entirely.

Pure sine or modified sine inverter?

Always pure sine. It produces clean power that's safe for electronics, chargers, and motors. Modified sine can damage sensitive gear and run motors hot — the savings aren't worth the risk.