Why the roof size isn’t the right target
Colorado’s net-metering statute caps systems at 200% of a customer’s expected annual consumption, and some utilities apply their own, tighter limits in practice — Xcel’s installer materials refer to 120% of prior usage. Beyond what you consume, surplus credits pile up and can only be cashed out at year-end at the utility’s average hourly incremental cost, which is well below what you pay.
So a self-storage facility with a small lighting and office load might only justify a fraction of its roof. That smaller array can still pay back well because the per-watt cost of a large, simple flat-roof install is favorable.
Adding load can change the math
If you’re planning EV charging for a fleet or customers, electric heat, or climate-controlled units, your future load may justify a larger array. We size for the load you’ll realistically have, not the load you hope for.
What about the rest of the roof?
Some owners lease roof space to community solar garden developers, whose arrays serve subscribers elsewhere on the grid. Whether that’s available depends on your utility, the developer market and interconnection capacity on your local grid. We don’t broker roof leases, but we can tell you how much roof your own system would leave.
What to do next
- 1Gather 12 months of usage (kWh) and any planned load additions.
- 2Confirm your utility’s size cap and export credit rules.
- 3Have us size an array to your consumption and check the roof structure and membrane age.
- 4Model the investment with the commercial ROI calculator, including your CPA’s view on depreciation.
FAQ
Questions we hear
Can I sell all the extra power to the utility?
Not at retail. Under net metering, excess credits carry forward, and year-end surpluses are cashed out at the utility’s average hourly incremental cost (co-ops use their own avoided-cost rules), which is much lower. Selling wholesale power is a different, much more complex arrangement.
Is the 120% or 200% cap the one that applies to us?
State law allows up to 200% of expected consumption, but some utilities’ materials cite 120% of prior usage. Confirm with your utility’s current tariff before we design.
Does a big flat roof make installation cheaper per watt?
Often, yes — easy access and simple layouts help. Ballast weight and membrane condition can offset some of that.
Is there still a federal credit for commercial solar?
Yes, §48E for solar placed in service by December 31, 2027 (as of September 2026). Talk with your tax advisor about credit rate and eligibility.