ripple4 wrote: ↑Tue Mar 30, 2021 5:40 am
Here is weather station data from Houston and it has good sun for 3 out of the 4 days. In my experience a few hours over 300w/m2 will put a meaningful amount of power in an off-grid battery. Texas had 4 hours of good sun on the 15th and 16th, the 17th was bad, and then the 18th was about 2 hours worth. A Tesla solar + powerwall customer or solar off-grider would have been well taken care of.
I used my actual usages during those four days and the actual average daily cost per kWH (3 days were $9/kWH). I then integrated the days solar wattages from the weather data (grosso-modo for sure!) and made some assumptions about efficiencies. A sweet spot for me would be a 9-10kW array with a V2X enabled Leaf plus - that would be sitting in the garage anyway - as roads were impassable. If we had lost power, then we would have had enough battery energy to keep the gas furnace and fridges going the entire time and saved around $800 of charges for the entire event. Since we did not ever lose power, and we were not at home the entire time, the result would have been making a little money by selling back overall and saving over $650 in energy costs for the 4 days. This would require the proper "smarts" for energy management and/or internet based controls with a small UPS backup for the router.