Simulated battery: 13.5 kWh, 5 kW, 90% round-trip efficiency, 10% reserve · retail 15.5¢/kWh · delivery adder 11¢/kWh
| Day's net bill (negative = credit) | Net metering | PJM wholesale |
|---|---|---|
| Bill without battery | ||
| Bill with battery | ||
| Saved, realistic controller | ||
| Best possible, with hindsight | ||
| Share of best captured |
How it works. The simulated battery replays your logged 5-minute solar, home-load and price data. It charges only from surplus solar, carries over the charge left from the previous day, and energy still stored at the end is credited at what it will be worth when used. Realistic controller: stores midday surplus and powers the home with it later; under wholesale pricing it also sells to the grid during price spikes, judged only from prices seen so far. Best possible: the mathematically optimal schedule for the same day, computed with hindsight, as a benchmark. Net metering (Dominion's current 1:1 annual netting) credits exports at the retail rate, so a battery can't earn on timing; it only loses a little to charging losses. PJM wholesale sells exports at the live price and charges imports the price plus the delivery adder.