Time-of-use + batteries: a $1,800 / yr arbitrage
A Stockton family cut their PG&E bill from $420 to $90 per month with TOU scheduling and a 2× Powerwall.
A Stockton family cut their PG&E bill from $420 / monthly to $90 / monthly — a $1,800 / year savings — with TOU rate scheduling and a 2× Powerwall. Here is the math, the schedule, and the lessons.
The setup
2.4 kW south-facing solar array, 2× Tesla Powerwall 3 (27 kWh total), E-TOU-C rate plan. Their original bill averaged $420/mo with a flat E-1 rate. We re-papered them onto E-TOU-C in week one.
The schedule
Solar charges the batteries from 9 AM to 3 PM. From 4 PM to 9 PM — PG&E peak window — the house runs on battery. Off-peak (12 AM to 3 PM next day) the grid charges batteries to 100% if solar was insufficient.
The numbers
Annual production: 11,200 kWh. Annual consumption: 14,800 kWh. Annual grid import: 3,600 kWh (off-peak only). Annual grid export: 0 (we use everything). Annual cost: $1,080 ($90/mo average).
What we learned
The first PSPS event ran the house for 34 hours without the grid. The family did not notice until we told them. That is the whole point.