Quick answer: An RV running a microwave (1,000W), laptop (65W), and lights (50W) simultaneously needs a 1,500W inverter — sum 1,115W and apply 25% safety margin. Add an air conditioner and you will want 2,500-3,000W with high surge capacity.
RV Inverter Size Calculator
Size your RV inverter by selecting your appliances. Get a wattage recommendation and guidance on pure sine wave vs modified sine wave.
How we calculate inverter size
The calculator sums running watts for all simultaneous loads, applies a 25% safety margin, and checks the surge rating requirement from any motor-driven appliances in your list.
Surge requirements are flagged separately — if your list includes a compressor or motor, the inverter's peak surge rating must exceed that appliance's startup draw.
Frequently Asked Questions
- What size inverter do I need for an RV?
- Add up the running watts of every appliance you might use simultaneously — that is your minimum inverter size. Then apply a 25% safety margin and check that the inverter's surge rating covers the startup current of any motors (refrigerators, air conditioners, pumps). A typical RV with a microwave (1,000W), laptop (65W), and lighting (50W) needs at least a 1,500W inverter. If you want to run an air conditioner or electric skillet, move up to 2,000–3,000W.
- Do I need a pure sine wave inverter for my RV?
- Yes, for most modern RV use. Modified sine wave inverters cost less but produce choppy AC power that damages or interferes with variable-speed motor drives, CPAP machines, certain battery chargers, and sensitive electronics like laptops. Pure sine wave inverters produce clean AC power identical to the grid and are safe for all appliances. The price difference has narrowed significantly — pure sine wave is now the right default for any RV installation.
- Can I run my RV air conditioner on an inverter?
- Yes, but it requires a large inverter and substantial battery capacity. A standard 13,500 BTU RV rooftop air conditioner draws 1,400–1,700W running and can surge to 3,000–4,500W on startup. You need a 3,000W inverter at minimum (with a high surge rating) and a battery bank of at least 200Ah LFP to run it for 2–3 hours. Soft starters reduce the surge draw dramatically and are highly recommended when running AC on battery power.
- What is the difference between pure sine wave and modified sine wave?
- Pure sine wave inverters produce smooth, sinusoidal AC power with low harmonic distortion — identical to utility power. Modified sine wave inverters produce a stepped or squared waveform that approximates a sine wave. The result is higher harmonic distortion, which generates heat in motor windings, causes buzz in audio equipment, and confuses the power factor correction circuits in modern chargers and appliances. For RV use with any sensitive electronics, pure sine wave is the correct choice.
Reviewed April 2026
Methodology and source note
PowerSizing calculators use shared formulas, documented assumptions, and current planning inputs that are summarized on the methodology page. Use these tools for first-pass planning, comparison, and sanity checks, then confirm local code, pricing, utility tariff, and installer specifics before you buy equipment.