We have one. For the January billing cycle, it used 42kwh to recharge after power was pulled to the grid (Tesla app number). That amount was deducted from our usage. We “sold back” 33kwh (GMP app number). The only deductions on the bill are the $2.00 Tesla efficiency credit thats on every bill. 76Kw is basically the difference between our usage amount and what the bill says we used, so there’s that.

The system is in the basement, tucked away in the corner. “They” came in, took some measurements and photos of the wall, path to the area, driveway, etc… etc… Had me point out all the things we wanted to stay on and what was good to be off. A few months later, 3 fellas showed up, went down to the basement and worked their magic. When they were done, one guy walked me through everything. They ended up adding 3 panels next to the main panel. Two deal directly with the power wall. The third was a sub panel that holds everything they pulled from “inside” the power loop, baseboard heaters, heat pumps, stuff like that. The install process, from them showing up with the boxes to leaving was a whole afternoon. The folks were all licensed electricians from Burlington (I’m in Quechee), and the work they did was tight and up to code.

Last time the power went out, the big ice storm, we turned off and unplugged everything except the two 11w LED lights in the room with our wood stove. The water pump worked, but the water heater is on a separate power system (GMP charges 0.08 less per kwh for the water heater if you let em turn it off a few hours per day) so we had running water. Our only extraneous power was two ipads and two cell phones. Our total power consumption per day was down to around 1.5kw. That number is the one you need to know if you want to figure out how long the batteries last.

All said and down, we plan for 4 days of off grid power. We “can” stretch it out by unplugging the basement freezer, lowering the pump pressure on the well and such, but we’re not gonna do that unless GMP has projected more than 4 days repair.

We’ve had to schedule a service call. No idea why, just started getting emails and text messages from the automated system saying we needed it. I can tell ya more after March 1st.

We did opt to pay for the system up front vs stretching out the bill. We did ask about adding batteries after the Jan power outage, but GMP’s limit is two and they don’t seem amenable to me adding batteries they didn’t provide. Since Tesla stopped selling the systems independently (you have to buy the solar panels now to get the batteries), it’s not an issue. The installer said GMP didn’t have plans to recover the powerwalls, but that was a few years ago and the installers didn’t work for GMP so take it for what it’s worth.

Overall, if I had to do it again, and had the means, I’d definitely go with two batteries.