We’re getting closer! Our attempted net-carbon-neutral house in St. Michaels, Maryland, won’t be finished for another two months, but its energy systems are now starting to spool up. Although it’s still too soon to report any systematic results, data reported on our utility and solar provider apps look promising.
This month’s illustration (attached) is a snapshot of the past few days from our page on Choptank Electric Cooperative’s website. The indication is that our 50 SunPower solar PV panels have continued to overproduce electricity, which we’re selling back to the grid via Choptank (also see last month’s report). Then, this past week, we started up our 8-well geothermal ground-source heat pump system. Things changed a little (see sawtooth pattern in the figure) but this still looks highly positive – i.e., we’re producing from solar energy much more electricity than demanded on site, even despite enjoying a nice, cool house in 90o weather!
Preliminary, it appears likely that electricity produced by our panels will continue to more than meet the house’s space conditioning and water heating energy demands. On sunny days, this will be especially so, including around the clock after our three Tesla Powerwall batteries are delivered and installed – but on dark, cloudy days, we’re unlikely to make HVAC ends meet without buying electricity from the grid.
Looking ahead, we expect our electricity uses to increase after our kitchen (mostly electric) is installed next month, and after the house lights up at night in late September, and as soon as we move mid-October and plug in everything, including the cars! With all this, if our solar panels are still overproducing, then we’ll keep selling the excess back to the grid. We should have a reasonable indication in another two months or so.
Sometime in 2019, we’ll be able to present results on a more systematic basis in terms of pay-back periods and the project’s implicit avoided cost of carbon.