Size your solar system from your annual electricity usage, not a single month. Find your yearly kWh on your utility bill, then design for that total. Under NEM 3.0 the ideal system is often paired with a battery and sized to cover what you use rather than to export power.
The right solar system starts with one number: how much electricity your home actually uses. This guide shows you how to read your bill, why annual usage matters more than any single month, and how NEM 3.0 changes the ideal system size.
Find Your Annual Usage
Your bill shows kilowatt-hours used. Because usage swings with the seasons, the figure that matters is your total over a full year. Most utilities show a 12-month history online, and that history is what a good design is built on.
Understand Time-of-Use Rates
Most California homes are on time-of-use rates, where power costs the most in the evening. That timing is why a battery is valuable: it lets you cover those expensive hours with stored solar rather than grid power. Reading the rate plan on your bill tells you when your most expensive hours are.
Why Bigger Is Not Always Better
Under NEM 3.0, oversizing a system to export extra power no longer pays well, because exports earn little. The smarter target is to cover your usage and self-consume as much as possible, usually with storage. A system sized to your real needs costs less and returns more.
- Use your full 12-month kilowatt-hour total, not one month.
- Note your time-of-use plan and your most expensive hours.
- Size to cover usage and self-consume, not to maximize exports.
- Plan for changes like an EV or electric heating if they are coming.