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RV Inverter: How to Choose the Best Option

So, you want to start dry camping? or perhaps just feel more comfortable “off the grid”?

That doesn’t mean you have to give up your TV, microwave oven, hair dryer, or some of your other 120 VAC (traditional items you plug into a wall socket) equipment.

You could of course buy a generator to power your gear, or even just to keep your batteries charged.

RV-Invertor-How-Choose

However, there are often limitations on how long you can run one and the expense of doing so. You might consider installing an RV inverter to compliment your power system.

What Is an Inverter Anyways?

Photo Credit: modmyrv.com
Photo Credit: modmyrv.com

Virtually every RV comes equipped with a converter.

Not to be confused with the “RV inverter”, the RV converter as the name implies, converts 120 VAC electricity into 12 VDC(think 12V cigarette lighter receptacle).

It charges your batteries and powers your lights, water pump, and all the rest of your 12 volt equipment.

The RV’s inverter does just the opposite. It converts 12 VDC from your battery into 120 VAC, standard household type electricity.

Before you buy your RV inverter, you need to decide what kind is most appropriate for you. Inverters come in two flavors and in a wide variety of sizes.

Difference Between Modified Sine Wave and True Sine Wave Inverters

The first  flavor utilizes a modified sine wave (MSW) output. The other has a true sine wave (TSW) output. Which one you need will depend on what equipment you will want to run off your RV inverter.

The output of the TSW inverter is indistinguishable from normal household current and, if sufficiently large, will run anything you connect to it. The down side, is that they (especially the big ones) get rather pricy in comparison.

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RV Inverter: Sine Wave Type Diagram

Photo Credit: The Good Luck Duck
Photo Credit: The Good Luck Duck

Not all Modified Sine Wave (MSW) inverters are created equal. A true sine wave is illustrated above (red line). Also shown are two different modified sine waves (blue and green). The modified (blue line) wave is much closer to the true sine wave (red line), and is less likely to cause problems with your electrical powered items.

For anyone not formally trained in electrical engineering it may be simpler to know that a traditional power grid, like the one you enjoy when you plug in at a hotel or at your sticks and bricks house, would look like the red line.

If you choose to purchase a MSW (blue or green line) RV inverter, the output you receive could cause intermittent issues with your sensitive electronics such as televisions and computers as described below.

The trade off, as with anything, is cost. TSW inverters tend to be significantly more expensive than their MSW counterparts .


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6 thoughts on “RV Inverter: How to Choose the Best Option”

  1. So, I am brand new to all of this but want to see if my thinking is correct. I just bought a 08 dodge sprinter that I will be converting over the next few months. I am not looking to put a microwave in it, only a fridge, tv, DVD player and some outlets. My idea is to run a two battery (deep cycle marine) bank in addition to the main engine battery, with a 1000w inverter off of it. I will be able to recharge off the engine daily, but with the engine off at night, will this be enough to power my needs? Really appreciate any feedback as, like I say, I am VERY new to all of this

  2. Joel,thanks for sharing your knowledge! I am planning to purchase and renovate/update a mid 90″s Airstream Ecella 1000 for both personal and business uses. I will be visiting this page often as I modernise the trailer for off the grid comfort.

  3. I am converting a 12 passenger bus to transport my elderly parents.

    They want a power lift recliner which has a 1.5 amp rating on 120 volts AC

    I am installing two of these chairs.

    what size inverter should I install?

  4. Inverter size is measured in watts and should be large enough for the maximum combined power draw of your devices. There should be a watts rating plate on each appliance you have, so just add up those that can be running at the same time. Devices with motors or compressors may be rated in Volt-amps (VA). For estimating purposes add 10% to the VA rating and use that for the watts. For example, if the rating sticker says 200 VA, add 10% (20 VA) for a total of 220 watts.

    Your microwave is the big power hog of the devices you mentioned, so a practical approach is to make the inverter large enough to handle the microwave and make sure the other devices are turned off for the brief time you will need to use the microwave. That allows you to buy a smaller inverter than otherwise necessary.

    Your batteries are going to be the limiting factor in both amps and time. As the amp draw goes up, battery voltage falls and at some point the voltage will drop below the inverter’s minimum requirement (typically 10.5 dcv) and the inverter will shut off. The batteries also have to have enough stored energy to be able to sustain that amp rate for however long you need to run the devices, so you need enough amp-hours to last until you can recharge the batteries. An amp-hour is simply one amp for one hour, so a power draw of 100 amps for 0.5 hours is 50 amp-hours (AH). You can see that the microwave will quickly deplete even a large battery, whereas the DVD player uses very little AH.

    A pair of typical RV batteries (Group 24 marine type) has an amp hour capacity of 170 when new and fully charged. After some use, this number usually decreases somewhat. In general you cannot use the full capacity without shortening the battery life, so the rule of thumb is to figure on 50% of the rated capacity. You can use 60-70% in a pinch, but if you do that often you will be buying new batteries fairly soon.

    In practice I don’t think you will be able to run your microwave with just two batteries, at least not for more than a minute or two. The other devices should run nicely.

  5. I am in the process of purchasing an ACE 29.2 and would like to add an inverter for when I dry camp. Looking to power a Cpap for 7hrs., 32″TV 3hrs, Micro 30 mins. DVD 2hrs. Coach is equipped with 2 house batts. I don’t know the amp hr cap. Approx. what size inverter would be appropriate. How do you monitor the batteries condition volts remaining in batts. Thanks new to RVinng

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