What a net metering cap actually limits
The typical cap range
For 10,800 kWh a year at a typical 125% cap, the maximum allowed system is about 10.0 kW, around 25 panels. At a more generous 200% cap, that rises to about 16.4 kW, nearly 65% more capacity for the exact same household usage, a real range official state program documentation confirms directly, with states like the District of Columbia phasing caps up to 200% specifically to accommodate future load growth.
Why caps vary so much between states and utilities
Caps are set by state regulators, not a single national standard. Some states hold systems to 100% of usage to limit excess export onto the grid, while others allow up to 200% specifically to leave room for future load growth like an EV or a heat pump conversion. Rhode Island and several other states cap new systems at 125%, while Maryland's regulations permit up to 200% of a customer's annual baseline usage. There is no substitute for checking your specific utility's actual net metering agreement, and the DSIRE database entry for net metering lists the cap that applies where you live.
When a flat kW limit overrides the percentage
A 30,000 kWh a year home at a 200% cap would otherwise qualify for about 45.6 kW, but a state with a flat 20 kW residential limit caps it there instead, regardless of usage. High-usage households are the ones most likely to actually hit a flat kW ceiling before the percentage cap would stop them.
What happens if you exceed the cap
Your utility may deny interconnection approval, require the system to be resized before approval, or shift the excess capacity to a less favorable compensation structure, sometimes an avoided-cost rate well below retail, a distinction the net billing vs net metering comparison explains directly. Sizing at or just under your confirmed cap avoids this entirely rather than finding out during the approval process. If your usage is set to grow, the gas-to-electric conversion tool can help estimate that future load now.
What to do with this number next
Once you know your maximum, compare it against what the full solar panel calculator says you'd actually need, and check the federal ITC calculator for state-specific net metering rules.