Table of Contents

An RV inverter has two jobs that a brochure often folds into one wattage. It has to run the appliances that are on together, which is the continuous rating. It has to start the motor that draws a short, higher current, which is the surge rating. Both numbers are on the inverter’s nameplate and on the appliance nameplates. Neither number is “about 2,000 watts because it is an RV.” A van with a compressor fridge and a laptop is a different inverter from a coach with a microwave and an air conditioner. If you cannot add the nameplates, you cannot size the inverter.

Continuous power and surge on an RV inverter

List the AC loads that may run at the same time. A fridge compressor, a water pump if it is AC, a television, and device chargers might overlap. Add their running watts. That sum has to sit under the inverter’s continuous rating at the temperature where the inverter will actually live, which on an RV may be a hot bay with poor air. Heat derates electronics. A Sandia and NREL thermal study found component temperatures rising with the power they dissipate, following the day and the year, and depending on airflow. A nameplate measured in open air is optimistic inside a closed compartment. Leave the clearance the manual asks for. Do not defeat a thermal limit to finish a meal.

Then read the start requirement of the largest motor. A compressor can draw several times its running current for a moment. The inverter’s surge rating has to cover that moment, for as long as the motor actually takes to start. The appliance sheet and the inverter sheet are the two documents. A surge rating that lasts a few milliseconds may not start a compressor that needs longer. If the sheets do not say the duration, you do not yet know. Do not fill the gap with a rule of thumb from another vehicle.

The battery has to supply the current the inverter is pulling, at the voltage the inverter requires. A deep-cycle house bank is the right class of battery. A starter battery is not the house bank. That split is in deep-cycle batteries for solar. A large inverter on a small bank collapses the voltage and shuts down. The failure looks like a bad inverter. It is a battery that cannot deliver the amps.

An RV inverter is not a house grid inverter

A grid-tied inverter follows the utility. IEEE 1547-2018 requires it to detect an unintentional island and cease to energize within 2 seconds. An RV parked away from a pedestal has no utility to follow. The inverter has to form the AC waveform from the battery. A residential interactive inverter, even a large one, will not do that job because you bolted it into a bay. Read the listing. “Hybrid” only counts if the unit is built to form a supply when no grid is present, and if the DC voltage matches the bank you have.

Shore power is a second source. When the RV is plugged in, a transfer arrangement should let the pedestal run the loads and charge the bank without back-feeding the pedestal through the inverter. That is ordinary RV electrical design. It is not optional creativity with jumper cables. Solar, if it is installed, charges the bank through a charge controller. It does not connect to the inverter’s AC output. The module side is in solar panels for an RV. The controller still has to match the module voltage to the battery. A PWM controller on a high-voltage module wastes the difference. That fault is in solar charge controller problems.

Many US houses are served at single-phase 120/240 volts. An RV inverter sold for the North American market is often a 120-volt unit because the appliances are. A 230-volt inverter from another market will not become 120 volts inside the coach. Match the appliance plugs to the inverter output. The service distinction, for buildings rather than vehicles, is in single-phase versus three-phase solar inverters. An RV is not a three-phase building.

What to write down before buying an RV inverter

Line Where it has to come from
Continuous watts Sum of running watts for loads that overlap, from their nameplates, under the inverter’s continuous rating at the bay temperature.
Surge and its duration The motor’s start requirement and the inverter’s surge window. If duration is missing, the pair is not yet sized.
AC voltage The plug the appliances actually use. Do not assume every coach is 120 volts, and do not assume a 230-volt unit will serve 120-volt appliances.
DC window and battery The inverter’s battery voltage and the bank’s ability to deliver that current. A starter battery is the wrong bank.

Efficiency of the inverter matters on a small roof because every watt it wastes comes out of the battery the solar has to refill. The figure is on the inverter sheet at a stated load. A peak efficiency at one operating point is not the efficiency at the light load you actually run all afternoon. Use the point that matches the coach, or accept that you do not know the loss yet.

Frequently asked questions

What size RV inverter do I need?

The continuous rating must exceed the running watts of the loads that are on together. The surge rating must cover the largest motor start for as long as that start lasts. There is no stock RV size. Add the nameplates in your coach.

Will a home solar inverter run an RV off-grid?

A grid-tied inverter is required to stop when it has no grid to follow. It will not form the coach’s AC supply. You need an inverter built to create that waveform from the battery, at the voltage your appliances use.

Can the RV inverter run the air conditioner?

Only if its continuous rating, its surge duration, and the battery current all cover that compressor, for the hours you want it. Many coaches cannot. Check the three nameplates. A solar array does not change the inverter’s surge rating.

Sources and references

Why a grid-following inverter stops within 2 seconds without a grid: NREL and Sandia, IEEE 1547-2018 primer. Heat and airflow inside power electronics: Sandia and NREL thermal study. One US utility’s description of residential service as single-phase 120/240 volts, which is a building service and not an RV standard: SWEPCO electric service handbook, 2024.