RV and Camper Inverter Size Calculator

I need power that doesn’t keep the campground up at night! Does this sound familiar?

Finding a camper inverter or measuring just how big of an inverter you need for your RV can seem like a difficult thing to understand. Where do you begin? How does an inverter work in an RV? Why do you need an inverter in your RV? What is an inverter in an RV anyways? Understanding just how off-grid power systems work is an important process for anyone who owns an RV, camper or motor home. Our handy guide will teach you just what you need to know about these useful pieces of equipment, from what size camper inverter you’ll need to how many RV batteries you need.

How does an inverter work in a motorhome? You can have power and not run the generator by using an AIMS DC to AC power inverter. Most RVs come with a converter, but not necessarily an inverter/converter combo. It’s important to distinguish between these two pieces of equipment.

Don’t mistake a converter with an inverter. A converter converts 120 VAC electricity into 12 VDC. The converter charges your batteries and powers lights, pumps, and all of the 12-volt equipment.

The RV’s inverter converts 12 VDC from your battery into 120 VAC, standard house electricity, allowing you to use it for equipment or appliances. A converter is useful for running your camper on the move, but a camper inverter is necessary to power your equipment without the added noise of a generator.

In order to buy the “right” inverter for your RV, you’ll need to determine the size of the inverter. To decide what size you need, total the wattage requirements of all the equipment you want to power, and then add another 20%. Next, you’ll need to decide if you need a pure sine or modified sine inverter. Most pure sine inverters will power any type of device. Modified sine inverters are better for pumps, motor, tools or equipment that has a DC brick power supply (from experience Macintosh products excluded). For more details on the difference between the two, you can check out our convenient guide on the topic. Microwaves are temperamental and we recommend using a pure sine.

Get wattage appliance estimates here to help you plan. Pumps, compressors, heaters, microwaves and some tools have high surge requirements to get them started so make sure you include these in your calculation (3x to 5x surge in most cases). You want to use the surge rating of all the equipment to size your inverter. Buy an inverter that has a continuous rating that matches the surge total of all equipment and then add another 20%. Details on finding the right inverter in general can be found in our helpful tips section, along with other useful details about inverters themselves.

Example: Total appliances running at the same time including the surge is 3600 watts but the running watts are only 2000 watts. You would get an inverter that is 3600 * 1.20 = 4320 watts. Obviously, we don’t have a 4320-watt inverter so we would recommend a 5000 watt. Your continuous running amp draw is 2000 watts/12DC = 166DC amps. Note this number for the next section.

How Many Batteries Do You Need?

You also want to determine if you have enough battery power available. Using the example above, you don’t want to install a 5,000-watt inverter if the 166DC amps needed to supply it will run down your batteries in 30 minutes.

To estimate your anticipated power consumption, take the current (from the example above) 166 DC amps and multiply by the number of hours per day that you expect to use it. Let’s say you will run 2000 watts, 166 DC amps for a total of 2 hours per day. You will need 166 * 2 hours = 332 amps total. You will also want to check the efficiency of the RV inverter that you are selecting. Because the process of converting from 12 VDC to 120 VAC generates heat, the inverter will always draw more watts from the batteries than it can deliver. Some brands have greater losses than others (usually 8 to 10%). If you have a battery bank of 400 amps, you will be able to run your 2000 watts for 1.2 hours, but we don’t recommend fully depleting your battery bank. Take your total available battery amps of 400 and divide by your total amp need of 332 and you get 1.2 hours. 400/332 = 1.2 amp hours. We recommend no less than 50 depths of discharge. If you follow this recommendation, you will get 1.2 hours * .50% = .6 hours of run time.

Features of RV Inverters:

We offer many inverters that have built in transfer switches that allow you to go back and forth between shore and inverter power. Our inverter chargers allow you to use the inverter with city or generator power to recharge the batteries/bypass when you have access to AC. Some have cooling fans, remote switches and add breakers for safety. Some also have direct connect terminal blocks to tie into a panel. Please call us if you need more info about RV inverters.

Whether you’ve asked yourself what size inverter you need for your RV or tried to understand how many batteries you need for your travel trailer, hopefully our helpful guide on the topic has offered insight. It’s important to remember that when utilizing power sources for your off-grid systems, rounding up is always the better option. With the right size inverter, the right number of batteries and the right cabling systems, you’ll have a noise-free electrical solution for your days.