How the bill offset calculator works
Offset ≠ bill elimination
Every utility bill has a floor: fixed connection charges, meter fees, and (in many markets) non-bypassable charges that ride on every kWh regardless of your exports. A perfectly-sized system can zero the energy line and still leave $10–30/month. Quotes promising "$0 bills" are selling the energy line and hoping you do not read the others.
Export credit is the swing variable
Under full net metering, exported kWh credit at retail — offset math is clean. Post-net-metering tariffs (California NEM 3.0 and peers) credit exports far below retail, sometimes by time of day. The same system can be a great investment under one tariff and mediocre under the next; the export-credit input exists to test both worlds.
Sizing to the honest offset
Where exports credit poorly, self-consumption is king: production that displaces on-site usage is worth retail; exports are worth the credit rate. That shifts optimal sizing toward usage-matched systems (and batteries, in some cases) rather than maximum roof coverage. Run this calculator at several production levels before choosing a quote.