An AC Inverter will allow you to power your AC appliances from your camper conversion’s DC electrical system. Depending on what you’re powering, you may want a “pure sine” inverter or maybe you can get away with a much cheaper “modified sine inverter”. Some higher end inverters will also allow you to charge your DC system via AC (“Shore Power” in RV parlance). More about all that later, first you’ll need to figure out what AC appliances you’ll be powering. For us it looked like this:
AC Requirements for our Camper Conversion
|Motorized? Sensitive?||Peak Watts||Sustained Watts||Bring It?|
|cpap (no heater)||Yes||80||less||yes|
Modified Sine or Pure Sine Inverters for Camper Conversions
Take a look at your list and see what’s motorized or otherwise sensitive. These items may not be able to run off a modified sine type inverter. Or if they can, it may shorten their life or cause problems. If you have doubts be sure to research each specific item on your list. For example, we decided to sell our blendtec for a cheaper blender not only because it reduced our peak watt requirement, but because we would have needed a Pure Sine inverter to protect it from damage.
“Wait, you bought a new, sacrificial blender just so you didn’t have to buy a pure sine inverter? How much more could they really cost?”
Sorry to be the barer of bad news….. They cost up to 10x more. At that price though, most have the additional feature of “shore charging”…
Charging your Camper Conversion’s Batteries Via AC “Shore Power”
Most expensive pure sine inverters are also able to charge your batteries via an AC hookup. This can be great for topping things off before you hit the road or when at a camp site with “shore power” hookups. And it’s absolutely essential if you don’t have solar or alternator charging. Be sure to calculate the right wire size on these, it needs to be sized for the larger amperage between the two modes with the correct size fuse (but you knew that right)? Take the safety quiz!).
Sizing an AC Inverter for a Camper Conversion
So now you’ve figured out what type of inverter you want, the next question is what kind of capacity do you need? Capacity is rated based on peak and sustained wattage, so just sum up all the “peak watts” in your table as well as the “sustained watts”. If you only know peak, it’s probably safest to use that number for sustained. If you only know sustained and it has an electric motor, double the value to get peak.
For us we ended up with a max peak of 1000watts and max sustained of 1000w (both from the blender), but only if we never used the blender and the kettle at the same time. That was an easy compromise to make given how much more expensive a larger inverter would be. We also decided to leave the espresso machine at home for inverter sizing reasons as well as common sense, but we still wrote a whole big post whining about it.
Reduce your AC Needs as Much as Possible
Not only is the DC->AC conversion process only 80% efficient, an inverter always draws some power when it’s on, so if you buy an inverter without fancy load sensing and “standby modes” you’ll be flipping the thing on and off all the time to save battery power.
For us, spending ~$100 on ways to reduce our AC demands made more sense than spending $800 extra dollars on a 2000 watt pure sine inverter. Ours is a Truck Bed Camper Conversion after all.
- Replace AC/DC converters with DC/DC step down converters
- Any AC appliance that uses an AC/DC transformer (anything with a “brick” like a laptop or a “wall wort” like a baby monitor) should be adaptable to run directly from your DC system. We bought this universal laptop charger that works for both the laptop and David’s CPAP. It was a big win getting the CPAP off the inverter – it’s a low draw over a long period, which is particularly inefficient with an inverter.
- Buy Lower Wattage Versions of Stuff
- We bought a 400 watt blender at goodwill for $10 and saved hundreds on buying an inverter that could handle a blendtec (and protected it from damage).
- Use Low Power Modes