Understanding quick solar sizing from your bill
What size system a typical monthly bill implies
A $450 monthly bill at a $0.13/kWh rate implies about 3,461.5 kWh of monthly usage, or roughly 41,538 kWh a year. At 4.8 peak sun hours and an 80% system derate, that points to a solar system of about 29.6 kW to offset the full bill. Once you have this ballpark, the commercial solar payback calculator can turn it into a rough financial picture, and the SBA's 504 loan program is worth a look if you'll need financing, since it offers fixed-rate terms specifically for equipment purchases like a solar array.
How accurate a bill-only estimate really is
It's a good starting ballpark but not a final design figure, since it doesn't account for usage patterns across the day, seasonal variation, or your roof's actual available space and orientation. It's useful for an early gut check before getting quotes, not for finalizing a purchase, similar to how the EV fleet charging solar sizing tool gives an annual-offset estimate rather than a real-time match. For the system sizing side of this decision, see solar panel calculator. Building type is a rough guide at best. The solar panel calculator in our System Sizing section can help you confirm the size from your actual electricity use.
Why use the bill instead of square footage for a first pass
The electric bill reflects actual energy consumption, which is what the solar system needs to offset, while square footage only indicates how much roof space might be available. For a very quick first estimate before a site visit, the bill is often the simplest number a business owner already has on hand. Once you're ready for more detail, the system size by square footage tool brings the roof-space side of the equation into the picture, and the Department of Energy's guide to going solar covers the broader cost and savings factors that feed into a decision like this one. Before you budget, check what you can claim back. The rebate stacking tool in our Rebates & Incentives section estimates the federal credit and state rebates for a system like this one.
What to do after getting this quick estimate
Getting an on-site assessment or a detailed proposal from a licensed installer is the natural next step, since they'll confirm actual usage patterns, roof condition, and available space. This quick estimate is meant to help decide whether it's worth pursuing that next step, not to replace it, and the roof mount vs. ground mount cost tool is a natural follow-up once mounting options come into play, alongside the 25-year lifetime savings calculator for a longer-horizon view once you're past this quick first pass, and the solar panel calculator in our system sizing section to translate your ballpark size into an actual panel count.