An RV inverter should cover the largest group of AC loads you will run together, plus motor and compressor surge. For many RVs, 2,000W handles outlets and kitchen appliances, while 3,000W provides more flexibility, but the battery bank and wiring must support the same power.
A larger inverter does not create more energy. A 3,000W load on a 12V battery can draw close to 280A after conversion losses, so battery discharge limits, cable size and fusing often set the real system ceiling.
Calculate the RV Inverter Size
- List each 120V appliance that will run from the inverter.
- Use electrical input watts, not cooking output or Btu rating.
- Add the loads that may operate at the same time.
- Identify the highest startup surge and its duration.
- Select a pure-sine-wave inverter with adequate continuous and surge ratings.
Example: a 1,500W microwave, 120W television and 100W of chargers total 1,720W. A 2,000W inverter may be sufficient if its temperature rating, surge capacity and the microwave’s actual input are compatible. A simultaneous toaster or coffee maker would overload that plan.
Air conditioners require model-specific running and starting data. A soft start may reduce compressor inrush, but running an RV AC from batteries still consumes substantial energy.
Size the Battery Bank for Current and Runtime
Approximate DC current with:
DC amps = AC watts ÷ battery voltage ÷ inverter efficiency
At 90% efficiency, a 2,000W load draws about 185A from a 12V bank, or about 93A from a 24V bank. A 3,000W load draws about 278A at 12V.
Estimate nominal battery energy with:
Battery watt-hours = AC watts × hours ÷ inverter efficiency ÷ usable battery fraction
A 1,500W air conditioner operating for three hours needs 4,500Wh of AC energy. At 90% inverter efficiency and 80% usable battery capacity, that is about 6,250Wh of nominal battery capacity before allowing for other loads, cycling and temperature.
The battery management system must support both continuous and peak current. Lead-acid capacity falls under high discharge and should be sized using the manufacturer’s discharge-rate data.
Inverter, Charger and Transfer Features
- Pure sine wave: Preferred for motors, microwaves, chargers and sensitive electronics.
- Inverter-charger: Combines AC charging and inversion, often with automatic transfer between shore, generator and battery power.
- Power assist: Some systems combine limited shore or generator power with battery power for short peaks.
- Split-phase support: A 50A RV has two 120V legs. The inverter architecture must match how the panel and loads are wired.
- Low-voltage protection: Settings must match the battery chemistry and BMS.
- Remote monitoring: Current, state of charge, faults and input limits help manage loads.
Decide whether the inverter will feed selected circuits or the whole panel. Exclude electric water heating, space heating and other impractical battery loads unless the system is explicitly designed for them.
Cables, Fuses and Safe Installation
Follow the inverter manual for minimum battery capacity, DC cable cross-section, maximum cable length and fuse rating. Keep DC cables short, protect the positive conductor close to the battery and use properly crimped lugs.
RV systems combine shore power, a generator, an inverter, solar charging and vehicle charging. Transfer logic must prevent sources from being connected incorrectly and must handle neutral-ground bonding as required for each operating mode.
Use a qualified RV electrical installer for high-current DC work or permanent AC changes. Low-voltage batteries can deliver enough fault current to melt tools and start a fire.
Bottom line: Choose inverter watts from simultaneous AC load and surge, then prove that the battery, BMS, cables and fuse can deliver the required current and runtime.
References: Victron inverter selection guidance and Victron inverter installation requirements.