Build Green Power - Inverters

Solar panels, wind turbines, and batteries all produce DC currents. However, the norm for power in the modern grid and the modern household is AC current. Thus, something needs to change the power coming from your green power system from Dc to AC. Enter: the inverter.

High End Inverters

Inverters can do a lot more than simply convert DC power to AC power. That said, I am not arguing that one should go out and invest in the best inverter you can find. But some of the additional functions it can have are nice.

Shut off: although this is not necessary, this is a function that is fairly valuable for an inverter. If the system becomes overloaded with excess voltage, it will shut itself off, protecting the system, your appliances, and the inverter itself. This is probably worth looking for in an inverter.
Stackability: Inverters have a maximum load. Thus, if you begin expanding your system, you could overwhelm your inverter. If it is stackable, it simply means that it can be put together with other identical inverters- just like the battery array. This may not be necessary, but can save money in the long-run.
Computer interfaces: More and more inverters are being made so that they can be controlled from a computer. A fully unnecessary function, it is nice. I’m obviously a computer person and would opt for it if possible- it’s certainly nicer than digging around on a box trying to program it like an old VCR.

Cheaper Inverters

The expensive inverters utilize full sine waves to ensure a completely clean AC current. Much cheaper inverters are on the market, called "modified" sine wave inverters. The mathematically inclined might be a little on edge reading that title. After all, I a sine wave is a sine wave, even if you apply some mathematical wranglings to it. The truth of the matter is that a "modified sine wave inverter" is using a wave form, but it's not a sine wave. The difference is arcane math that I don't want to try to explain on a website, but suffice it to say that the AC current produced isn't as "clean."

But what does that mean? It took me a bit to figure out the difference, but there is a bottom line to that. Basically, the modified current may work for certain appliances, but not others. It's generally ok for something like your toaster, but probably not your laptop. In fact, the owners manuals typically have an appendix that lists appliances that may not run well off one of these inverters.

I recommend against skimping on the inverter. But if you choose the cheap route, well- you've been warned.

Grid-Tie Inverters

This final point about inverters is absolutely critical if you are going to have a system that links into the grid, whether battery backed up or not. Having your current in its lovely sine wave AC form is not enough for a grid. Grids have specific wavelengths- and they can vary. If you decide to tie into the grid, you MUST ensure that the inverter you get is capable of grid-tie. Aside from the fact that it will not work, the electrical company will not be pleased to find you mucking with their system- and we’re aiming for a positive experience for all here, not an experience of having a utility company representative knocking on your door angrily.

That said, this is my favorite system for a variety of purposes. First, this is where you can truly expand beyond yourself to work on saving the environment. If your system overproduces and feeds back into the grid, that’s more power in the grid from clean sources and less power that has to come from fossil fuels. Second, if you do that, most utility companies allow you to sell back that power you’ve made. Thus, you are actually MAKING MONEY with green energy. How’s that for getting your just deserts after paying for dirty power for so many years?

Inverters Bottom Line

It is critical to have an inverter. No green power system will function without one. But unlike the charge controller, I am not as dead-set on the idea that it must be a super high quality component. As with all products, more expensive inverters tend to have more bells and whistles and sometimes are simply better products, wasting less of the produced energy. But if you are on a budget, evaluate exactly what you need before buying.