When we were setting up our all electric home for solar 12 years ago now, my first inclination was to set the goal of net zero energy or electricity use as global climate change is a major concern of mine. But I soon came to the realization the net zero cost was much more realistic financially, and to some extent not entirely inconsistent with the goal of minimizing one’s carbon footprint. The assumption at that time was that the electricity rates during certain time periods represented the inherent capacity of the system to generate the electricity for that time period. Rates were cheap at night as there was plenty of capacity at night as the overall capacity of the system was dictated by peak usage during the afternoon when businesses and factories, etc. are open and heating or cooling their buildings. Thus, rates were high during the day and that encouraged a growth in solar capacity. From an environmental point of view, adding solar was much better environmentally than adding new natural gas powered peaker plants to meet the energy needs during this time period. (Unfortunately, they did it anyway.)
So, for the first few years I enjoyed good rates for my solar production as peak rates were pretty well aligned with solar output. That has obviously changed over the years and with EV2-A, peak rates are now not at all a good fit for my solar production. Battery systems are almost a must currently for solar to make sense financially.
Getting back to precooling, it seems far better to be precooling my home while the sun is shining and my solar output is at a max, e.g. early afternoon. During this time, I could be putting it into the grid for $0.17/kWh, or, by precooling our home at that rate, I can avoid cooling during the late afternoon and evening when it would cost me $0.48/kWh and be competing with increased demand elsewhere in the system. While there is an obvious financial reason to do so, there is also likely an environmental reason as well if that means that, hopefully, PG&E won’t need additional natural gas peaker plants to meet those needs.
The cool thing is that precooling really works and the house has never been so comfortable. So far I have been able to get through the peak periods without the AC coming on, or my even thinking about wanting it to come on. Since I am on Cost Savings the Powerwall is not only generating all the electricity I need for the peak hours, it is also covering the partial-peak hours before and after the peak time. So right now, all my electricity coming from the grid is at off peak rates. Far better to use what I can of my $0.17 juice to power my house and avoid paying $0.48 and $0.37 for the same use.
