How the numbers work
Lot and canopy size
Clicking the map pulls the parking area that contains that point from OpenStreetMap; drag the corners if it's off. Canopies go over the parking rows, not the drive aisles, so we cover 50% of the lot by default, with modern panels at about 200 W per square meter. Stall counts assume about 325 ft² of lot per space, aisles included.
Build cost and upkeep
Canopies cost more than rooftop solar because the steel and foundations are most of the job. Massachusetts' 228 canopy projects averaged $4.01 per watt, which is our default; the table above shows others from $2.78 to $5.14. Upkeep, insurance and repairs use the US Department of Energy's 2025 commercial benchmark of $40 per kW a year, rising 2.5% a year. Platform and financing fees aren't included.
Sunlight
Yearly output comes from NREL's PVWatts model for the lot's location, assuming a low-tilt canopy facing south with 14% system losses, and panels losing 0.5% a year. Real canopies in California, New York and Maryland make 1,500 to 1,800 kWh per kW a year, in line with PVWatts. If PVWatts is unreachable, we estimate from latitude and say so.
What the store pays
The store signs a long-term power purchase agreement: it pays a fixed discount off what its utility charges, rising 2% a year. We start from the average price businesses pay in the lot's state (EIA, 2024) and take 30% off by default, which puts California near the 16¢/kWh real school canopies signed. Where power is cheap, like Texas, the numbers don't work yet, and the page will show that.
Your returns
Owners fund the whole build with no debt and split each year's power sales, after upkeep, in proportion to what they put in. The yearly return is the internal rate of return on your money over 25 years, the life of a panel warranty, with nothing left at the end. Returns are before tax and are not guaranteed. For comparison, retail solar offerings like Energea target about 11 to 12% a year and have paid around 5% cash yields.
Federal tax credit
Under the 2025 tax law, a solar project that didn't start construction by July 4, 2026 gets the 30% investment credit only if it's running by December 31, 2027, and supply-chain rules apply. Individual owners usually can't use the credit, so the project sells it, at about 92¢ on the dollar. It's off by default because a new project may miss the deadline.
Carbon
Every kilowatt-hour from the canopy displaces one from the local grid. We use the lot's state emissions rate and generation mix from EPA eGRID 2023. A typical car emits 4.6 t of CO₂ a year (EPA).
Cooler pavement
We take the lot's typical-year weather from NREL and average the sunny June to August afternoons. Sunlit asphalt runs about 0.032 °C above the air for every watt per square meter of sunlight; shaded pavement stays within a few degrees of the air. The difference is how much cooler the parking spaces under the canopy get.
These are illustrative estimates to show how a canopy could pay its owners. They are not an offer to sell, or a solicitation to buy, any security. Any investment would be offered only through official offering documents, and returns are not guaranteed. Store names mark example locations only; Sun Lots isn't affiliated with any retailer.