The inverters are what makes the whole thing work. An inverters's basic job is convert DC (direct current) to AC (alternating current). DC is what you get from batteries and solar panels. AC is what you get from the power company and what things like washing machines, TVs, and computers typically run on. You can get inverters for all sorts of uses. For instance, you can buy simple versions that plug into your car's cigarette lighter socket and produce AC to run a phone or laptop.

The Xantrex (formerly Trace) SW4024 inverters we installed are basically the same thing, only they can can handle up to 4000 watts, which would suck a car battery dry in a matter of minutes. They'll also work the other way, converting AC into DC to charge the batteries.

The AC can come from either the grid (power company), or an AC generator. If both are hooked up it'll use the grid until the grid fails, then it will switch to batteries long enough to start the generator, then switch to the generator, charge the batteries back up, and wait for the grid power to come back, at which point it will switch back. All without having the lights flicker or requiring any manual intervention.

And that's just for warm-up! They can also be programmed to do things on a timed basis (running off the generator, or the batteries at certain parts of the day when electricity is expensive, for example, or only charging the batteries late at night when it's cheaper). click here for a full review. If you're interested in the detailed specs, you can go to the manufacturer's web site where you can find specs, manuals, and other etc.

The only problem with them for us was that they initially had a slight "compliance issue", necessitating a chip upgrade when we first got them. (I'm told this firmware update has since been incorporated as standard, but we got ours before the update so we had to swap the chips ourselves.) We thought this was to bring it into compliance with the latest version of the Underwriters Laboratory's UL-1741 and IEEE's 929 specs regarding grid-interactive parameters in the "sell" mode. At least, that's what Trace's web page on the subject said.

Upon closer inspection of the front panel however, we think we found the real "compliance issue"...