RV Inverter Size Guide

An inverter changes battery power into household AC power. The right size depends on both continuous watts and startup surge. A large inverter is not automatically better: it can consume more standby power, require heavier cabling, and make a small battery bank run down quickly.

Step 1: list simultaneous loads

Write down the AC appliances you want to run at the same time: laptop chargers, TV, CPAP, coffee maker, microwave, refrigerator controls, or an induction cooktop. Use the appliance label or manual rather than guessing. Add the running watts of the loads that truly overlap, then add a practical margin of about 20–25%. This gives a continuous-watt target.

Step 2: account for startup surge

Motors and compressors can briefly demand much more power when starting. Refrigerators, air conditioners, pumps, and some power tools are common examples. Look for a documented surge rating and duration, not just a vague “peak” number. If the inverter trips when a motor starts, a higher continuous rating alone may not solve the problem: battery current, cable voltage drop, and the appliance’s starting behavior also matter.

Step 3: check the 12V side

At 12 V, a 1,000 W AC load can require roughly 90–100 A after inverter losses. A 2,000 W load can approach 180–200 A. That means short, properly sized cables, correct overcurrent protection, secure connections, and a battery/BMS that can deliver the current. Never select an inverter by AC watts while ignoring the battery’s discharge limit.

Pure sine vs. modified sine

Pure sine wave output is the safer default for modern RV electronics, chargers, audio equipment, medical devices, and motor loads. Modified-sine units may run simple resistive loads, but they can create noise, extra heat, or unreliable operation. Confirm the inverter’s output waveform and the manufacturer’s compatibility guidance before connecting sensitive equipment.

How to install (wiring overview)

Inverter installs carry high DC current. The overview below shows the usual order: battery bank → large fuse or breaker near the battery positive → short, thick cables to the inverter DC terminals → AC output to a transfer switch or dedicated outlets, with the inverter chassis grounded per the manual. Size the inverter and cables for continuous watts, surge, and cable length.

Common pitfalls

• Running an air conditioner from a small bank: high-energy loads rapidly drain batteries and may exceed inverter surge limits.
• Ignoring standby draw: an inverter can use energy even with little or no AC load; use an enable switch or low-idle model when appropriate.
• Backfeeding shore-power wiring: a transfer switch or properly designed installation is required. Never plug an inverter into an RV outlet to energize the whole coach without a compliant transfer arrangement.
• Forgetting charger interaction: inverter/chargers can charge the batteries from shore power, but settings must match the battery chemistry.
• Skipping grounding and fusing: follow the manual and applicable electrical rules; have a qualified technician inspect permanent wiring.

Which inverter size fits your setup?

Most RV setups fall into one of these three cases. Find yours, then check the current specifications on the product page before you buy, and make sure your battery bank and cabling can support the size you choose.

• Light electronics and charging: a 600–1,000 W pure sine inverter with low idle draw is usually enough. See on Amazon.ca
• Larger loads running at the same time: a 1,500–2,000 W pure sine inverter, as long as your battery bank and cabling support it. See on Amazon.ca
• A full system with AC transfer and battery charging: an inverter/charger combines both, but installation is more involved. See on Amazon.ca

Quick rule of thumb

Choose the smallest pure sine inverter that comfortably handles the simultaneous running load and startup surge you have verified. Then confirm battery capacity with the amp-hour calculator, and have fixed AC wiring installed or checked by a qualified professional.