By Russ and Tiña De Maris
Considering the RV boondocking lifestyle? You’ve probably already been mulling over solar panels and bigger battery banks. That’s great for your low-voltage needs – lights, fans, all that typically 12-volt stuff. But today’s RVer generally won’t be satisfied with “just” 12-volt power. There are plenty of uses for “shore power,” and if you truly want to take advantage of your solar system, an inverter is a requirement.
New to the game? An inverter is a device that takes your 12-volt DC power – the kind that’s stored up in your RV “house” batteries – and converts it to power that can be used for items normally “plugged into” wall outlets: TV sets, corded power tools, microwave ovens, vacuum cleaners and, for some of us, CPAP machines.
Inverters come in a variety of sizes, from small ones that plug into a lighter socket and may kick out enough shore power to operate a laptop computer, to much larger ones that could theoretically operate your RV air conditioner. We say “theoretically” as you’d have to have a large enough bank of batteries to support the huge load – and a hugely substantial solar panel array.
Aside from sizing, another major consideration when choosing an inverter is the power output form: pure sine wave or modified sine wave. The former “looks” like the stuff that your power company sends to your sticks-and-bricks house: smooth curves, easily digestible. Modified sine waves don’t have that nice, smooth shape. The picture above tells the story. Somebody once described the difference as driving down the road with nice round tires (pure sine wave) versus tires that were square (modified sine wave). Which would you prefer?
Where the “rubber meets the road” for inverters is the final consumer – the shore power device being fed by the inverter. Some things don’t give a hoot if the road is bumpy: your vacuum cleaner will still suck and an electric fan may run fine, although you may notice it buzzing. But other shore power consumers may run hot, inefficiently or just not at all when fed modified sine wave power. Here’s a list of things that generally REQUIRE pure sine wave power:
Variable speed tools
Many cordless tool battery chargers
CPAP machines with humidifiers
With that in mind, why would anyone install a modified sine wave inverter? It’s that old thing: money. For example, we recently did our own inverter shopping. We needed an inverter that would provide 2,000 watts. Modified sine wave inverters in that range cost anywhere from $130 to $200. Pure sine wave inverters were definitely more, starting at about $250 and easily hitting $400. In the end, we considered all that we needed to run from the inverter and bought a pure sine wave unit. Don’t let the price difference frighten you off – just a few years ago the price difference between the two types was even steeper; the cost of the “better” technology has actually come down.
Keep in mind, while you may be able to make some equipment operate on modified sine wave power, it may not operate nearly as efficiently, and may run hotter. In the end, what you “save” in buying the lower-cost modified sine wave unit may be more than made up in the decreased lifespan of equipment that you operate with it.