Still waiting for our Tesla PowerWall 2 – months overdue. It will be interesting to see if it removes our need for the grid for most of the year. Once installed, we will move to a time of use tariff (TOU), possibly shifting the hot water from controlled load 1, which would allow us to use excess solar during the day to heat it, although at current winter demand there is only a marginal amount of excess.
Summer demand blew out this year, due to the extreme hot spells; usually, it is our lowest demand period.
Winter usage is dominated by controlled load hot water demand; this remains a continuing problem to solve. Currently, there are no solutions that make economic sense. We used virtually no heating from the grid, the slow combustion stove and heat transfer working well to keep us warm.
Overall, the next few months will reveal whether our current PV will be enough to make the house net zero for the year.
Update Nov. 2021
Well the Tesla Powerwall never arrived and after less than encouraging responses we pulled the plug. That was in 2018, I think, it seems an age ago, so long in fact, that I forgot that we had been waiting for one. In the interim we have upgraded our solar PV both in size and integrated with Enphase micro inverters; we removed all gas and installed an induction cooker as well as a solar diverter to heat our hot water with the excess solar from our PV. With 2 years of data, we can feel comfortable in declaring the household net positive for energy. We have used virtually no controlled load for our hot water and the solar diverter has worked well.
We are waiting to see Enphase’s new battery system in 2022, which has been available in the US for some time now; it promises a step change in expanding our grid independance.