Ok, a post about the project here. We built our house ten years ago, and have powered it ever since with wind and solar. Almost. During the short, cloudy days of November and December, and other times when we get a string of stormy days, we sometimes need to run a gas-powered backup generator. For years I’ve thought about adding enough solar to completely free us from the generator and fossil fuels, but in an off-grid setup the system becomes more and more inefficient as you add more panels, because you’re adding generation that you might only need to use 5% of the time. The other 95% of the time, all that potential power goes unused (for more about this inefficiency, see my post “Not Sexy” ). But, we were very close to net-zero despite the generator use, and I wasn’t quite sure how to change the system in a way that would make economic sense.
Then we got the electric cars. Which we love. And then I started wondering about powering not just the house with solar, but the cars, too. Suddenly, the thought of tying to the grid for more efficiency began to seem like a practical path forward. Then, I realized that a number of renewable energy rebates and incentives are set to expire at the end of this year, so it seemed like a good time to push ahead with the entire grid-tie, add-more-solar plan.
So, that plan, now underway, is to bring in the grid power in from the road, underground, to the barn. Then, I’ll reverse the cable run that currently takes power from the house to the barn, and use it to bring power the other way, from the barn to the house (the barn is between the house and the road). Then, I’ll add 10,000 watts of panels to the barn roof, and grid-tie them with Enphase micro-inverters. The current PV system, with the inverter in the basement, will stay largely intact, but will become a fairly robust PV and battery backup system for those times every year when the grid power goes down.
That’s the very short version, anyway. Oh, and then we’ll replace the propane hot water heater with a new, highly efficient electric heat pump water heater, which will virtually eliminate the propane bill.
If all goes well, monthly cash flow should about even out. We’ll pay for the home-improvement loan, but we’ll be able to mostly quit buying propane (we’ll still keep the propane range-top, for now), we won’t have to buy fuel for the generator, and we can charge the cars here and save the money that we normally reimburse my wife’s place of work. On the practical side, I can also quit fueling and maintaining the generator, and can quit climbing up on the scaffolding next to the barn all winter to rake the snow off the solar panels.
Then, after fifteen years the system should be paid for. After that—virtually free utilities and transportation energy, for decades.
That’s the rough outline, anyway. There’s actually a lot more to it, but I’ll discuss the details as they come along. Until then, I’ve got plenty to do…