The right RV inverter size depends on the total running and surge watts of the appliances you want to power at the same time. By adding up those numbers and matching them to your battery bank, you can choose an inverter that runs your gear reliably without draining your system too quickly.
In this guide, we’ll cover what an RV inverter is, how to calculate continuous and surge wattage, why a safety margin matters, how to size your battery bank, and which type of inverter to choose. We’ll also walk through real-world examples so you can confidently select the right inverter for your RV setup.
Key Summary:
- An RV inverter converts battery power (DC) into household power (AC) so you can run appliances like microwaves, laptops, and TVs.
- The correct inverter size depends on both continuous wattage (appliances running together) and surge wattage (startup power spikes).
- A 20–30% safety margin prevents overload, accounts for efficiency loss, and extends inverter lifespan.
- Inverter size must match your battery bank: roughly 100Ah of 12V battery capacity is needed for every 1,000W of inverter power.
- Pure sine wave inverters are best for sensitive electronics, while modified sine wave units are cheaper but only suited for simple loads.
What Is an RV Inverter and Why Size Matters?
An RV inverter is an electrical device that converts direct current (DC) stored in your batteries into alternating current (AC) — the same type of power you have at home. This allows you to run kitchen appliances, laptops, televisions, fans, and other AC-powered equipment directly from your batteries.
Why sizing matters:
- Undersized inverter problems: If the inverter is too small, it won’t be able to handle the combined load. It may overheat, shut down suddenly, or simply refuse to run larger devices like microwaves or air conditioners.
- Oversized inverter problems: Bigger isn’t always better. Oversized units are more expensive, often less efficient at light loads, and can drain your battery bank faster.
- Right-sized inverter benefits: A properly matched inverter balances performance, efficiency, and longevity. It powers all your chosen appliances reliably without unnecessary strain on your electrical system.
Step 1: List Your RV Appliances and Wattage Needs
The first step is to create a complete inventory of the devices you plan to run on inverter power. Each appliance has two numbers you should note:
- Running wattage (continuous draw): The steady power needed once the device is operating.
- Surge wattage (startup draw): The short burst of extra power needed to start motor-driven devices like air conditioners, refrigerators, or blenders. This surge usually lasts just a few seconds but can be two to three times higher than running power.
Where to find wattage ratings:
- Check the label or specification plate on the device.
- Look inside the owner’s manual.
- Use a wattage meter (such as Kill A Watt) for accurate, real-world numbers.
Table: Common RV Appliance Wattages
| Appliance | Running Wattage (approx.) | Surge Wattage (approx.) |
| Microwave (1000W) | 1,000 W | 1,500–2,000 W |
| Hair Dryer | 1,000–1,500 W | 1,000–1,500 W |
| RV Air Conditioner (13.5k) | 1,200–1,500 W | 1,500–2,000 W |
| Space Heater | 1,000–1,500 W | N/A |
| Toaster | 800–1,200 W | N/A |
| Refrigerator (Residential) | 200–800 W | 1,000–2,000 W |
| Coffee Maker | 800–1,200 W | N/A |
| Blender | 300–600 W | 600–1,200 W |
| TV (LED) | 30–100 W | N/A |
| Laptop | 50–100 W | N/A |
| Lights (LED) | 3–12 W | N/A |
This list will become the foundation of your calculation.
Step 2: Calculate Your Total Power Requirement
Once you have wattage numbers for your appliances, it’s time to calculate how much power your inverter must deliver.
Continuous Wattage
This is the sum of all running watts for the devices you expect to use at the same time. For example, if you run a coffee maker (1,000W), a laptop (100W), and LED lights (50W), your continuous load is:
1,000 + 100 + 50 = 1,150W
Surge Wattage
Next, consider surge power. Appliances like microwaves and air conditioners need a temporary burst of extra wattage to start. Identify the highest surge wattage among the devices you’ll run and add it to your continuous load.
Example Calculation:
- Microwave (1,000W running / 1,500W surge)
- TV (100W running)
- Lights (50W running)
Total running = 1,150W
Highest surge = 1,500W
Total surge requirement = 1,150 + 1,500 = 2,650W
Your inverter must handle at least 1,150W continuously and 2,650W in short bursts.
Step 3: Add a Safety Margin (20–30%)
Inverters are not 100% efficient. Most operate at 85–95% efficiency, and running them at their maximum rating shortens their lifespan. Adding a 20–30% safety margin ensures smoother operation.
Using the previous example:
- Surge requirement = 2,650W
- 20% buffer = 2,650 × 1.20 = 3,180W
- Final recommended inverter size = 3,500–4,000W
This overhead protects you from unexpected power spikes and prevents your inverter from straining under full load.
Step 4: Match Inverter Size to Your Battery Bank
Even the best inverter is useless if your battery bank can’t support it. Every watt of AC power comes from stored DC energy in your batteries.
Rule of Thumb:
- 1,000W inverter capacity ≈ 100Ah battery (12V system).
Table: Inverter Size vs Battery Bank (12V)
| Inverter Size | Minimum Battery Bank |
| 1,000W | 100Ah |
| 2,000W | 200Ah |
| 3,000W | 300Ah |
| 4,000W | 400Ah |
Formula for current draw: Amps (DC) = Watts (AC) ÷ Volts (battery system)
Example: A 2,000W inverter on a 12V system draws ~167 amps at full load (2,000 ÷ 12). Without a large enough battery bank, you’ll deplete your energy in minutes.
Step 5: Consider the Type of Inverter You Need
Pure Sine Wave Inverter
- Produces smooth, utility-grade AC power identical to household electricity.
- Safe for sensitive electronics (CPAP machines, TVs, laptops, induction cooktops).
- Runs appliances more efficiently and prevents buzzing or overheating.
- Costs more but is the best choice for most RVers.
Modified Sine Wave Inverter
- Produces a blocky, less stable form of AC power.
- Works fine for simple loads like lights, fans, or small tools.
- Cheaper upfront, but may shorten the lifespan of sensitive devices.
- Can cause interference in audio systems and inefficiency in motors.
Step 6: Practical Sizing Examples
- Weekend Camper: Laptop (100W), lights (50W), coffee maker (1,000W), blender (600W surge).
- Continuous load = ~1,150W
- Surge requirement = ~1,750W
- Recommended inverter = 2,000–2,500W
- Battery bank = 200Ah minimum
- Full-Timer: Microwave (1,000W/1,500W surge), A/C (1,500W/2,000W surge), TV (100W), fridge (500W/1,200W surge).
- Continuous load = ~3,100W
- Surge requirement = ~4,300W
- Recommended inverter = 3,500–4,000W
- Battery bank = 400Ah+ minimum
These examples show how quickly loads add up. Running an air conditioner alone often requires a very large inverter and robust battery bank.
Other Considerations When Choosing an Inverter
Beyond wattage and battery matching, also think about:
- Installation space & ventilation: Inverters generate heat; poor airflow can cause shutdowns.
- Built-in safety features: Look for overload protection, low-voltage shutoff, and fuses.
- Brand reliability: Established inverter brands often provide better customer support and warranties.
- Off-grid vs campground use: If you mostly stay at campgrounds with hookups, you may not need as large of an inverter as someone boondocking full-time.
Final Words
The right RV inverter size depends on your specific appliance list, your surge requirements, and the size of your battery bank. The steps are straightforward:
- List all devices.
- Calculate continuous and surge wattages.
- Add a 20–30% safety margin.
- Match to a properly sized battery bank.
- Choose between pure sine and modified sine models.
For casual campers, a 2,000–3,000W inverter with a 200–300Ah battery bank is usually enough. For full-timers or anyone running air conditioning, a 3,500–4,000W inverter with at least 400Ah is a safer bet.
Getting the size right will protect your appliances, prevent inverter overload, and maximize the life of your battery system — giving you a reliable RV power setup wherever the road takes you.
Related FAQs
Can I run my RV air conditioner on an inverter?
Yes, but you’ll need a large inverter (3,000W+) and a large battery bank, since A/C units require high surge wattage.
What happens if my inverter is too small?
It may shut down during operation, trip breakers, or fail to start high-draw appliances.
Can I oversize my inverter safely?
Yes, but an oversized inverter wastes energy at low loads and drains batteries faster if the bank is too small.
Do solar panels affect inverter size?
No. Solar panels recharge batteries, but inverter sizing depends only on what loads you plan to run.
Jack Rivers is a long-time RVer, a husband, and a dad who’s traveled solo and now with his family. He’s learned a lot from years on the road, sometimes the hard way. From quiet mornings parked by the woods to messy evenings with the kids and a busted heater, he’s been through it all. Miles writes to share the real stuff, the small wins, and the lessons that make RV life worth it, no matter who you’re traveling with.
