If you’ve read how a California bill works, the battery question follows immediately. Here’s the mechanical answer, without the part where someone tells you it pays for itself.
Most people arrive thinking a battery stores extra production to sell later. That isn’t what it’s for.
Under the Net Billing Tariff, the kilowatt-hours your system makes at midday are worth very little exported, and the ones you buy in the evening cost the most. A battery takes production from the cheap hours and hands it back during the expensive ones — moving energy from an hour where it’s worth little to one where it’s worth a lot.
That’s the whole mechanism. Everything else about batteries is a consequence of it.
The energy is not saved for later in any general sense. It is moved out of the hours where it is worth least and into the hours where it costs most.
Schematic. Shapes vary by roof, season, rate schedule and how you live.
These get sold as one thing and they aren’t. Decide which you’re buying before anyone quotes you.
The number that matters is how much electricity you use between roughly four and nine in the evening — not your annual total, and not the size of your roof. Anyone sizing a battery without asking about your evenings is sizing it from a catalog.
The arithmetic changes. Where exports are still credited at or near retail there’s far less spread to shift into, and a battery becomes mostly a resilience decision rather than an economic one. That’s a legitimate reason to buy one — it just needs to be priced and justified as that.
Send us the quote. We will tell you which parts are for the bill, which are for the outage, and whether the sizing matches how you actually use the evenings. No obligation either way.