The percentage that should drive the design
A solar system produces its highest value when the electricity it generates is consumed by your own household as it is generated, because that kilowatt hour offsets one you would have bought at the full retail rate.
The next best outcome is a kilowatt hour exported and credited under net metering, which Xcel credits at the retail rate and rolls into a Solar Bank. The worst outcome is a kilowatt hour that survives to year end, where the payout is the average hourly incremental cost of electricity from the previous 12 months rather than retail.
So a design should start from your last twelve months of bills, not from the square footage of south-facing roof you happen to have. Ask what percentage of your annual usage the proposed system covers, and ask to see the twelve months of consumption the design was built from.
A genuine reason to go beyond that percentage exists when your load is about to change, for an electric vehicle, a heat pump or an addition. Sizing for a concrete plan is sound engineering. Sizing for a hypothetical is a way of selling more panels.
What ending the federal credit changed
The 30 percent federal Residential Clean Energy Credit under Section 25D expired for property placed in service after December 31, 2025. For a cash or loan purchase, roughly a third of the historical support for a residential system is simply gone.
That does not merely make solar more expensive. It changes which design decisions matter, because oversizing used to be partly subsidised and now is not. Every extra panel is now paid for entirely by you and returns its surplus at year-end payout rates.
It also means older material is actively misleading rather than just dated. Calculators, guides and sales decks built before 2026 carry the credit as an assumption, and a projection that includes it is overstating your return by close to the size of the credit.
Ask any installer directly whether their savings model applies a federal residential credit. If it does, ask for the version without it before you compare quotes, because otherwise you are comparing two different worlds.
What is left, and it is not nothing
Full retail net metering remains. Xcel credits exported solar at the retail electricity rate, with the surplus rolling month to month and year to year into a Solar Bank subject to your election between continuous rollover and a year-end payout.
The property tax exemption remains. Under Section 39-3-102 C.R.S., independently owned residential solar of no more than 100 kW AC on residential real property, producing primarily for residential use, is exempt from Colorado property taxation. It arrives as an absence rather than a payment, which is why it is so often left out of a homeowner calculation.
The residential energy sales and use tax exemption remains, and Solar*Rewards remains available to Xcel customers as a payment in exchange for your Renewable Energy Credits, with an upfront incentive for those meeting income requirements or living in a qualifying community.
And the largest item was never an incentive at all. It is the electricity you stop buying, every month, for the life of the system. A quote that leads with incentives and treats avoided cost as an afterthought has the emphasis backwards.
The parts that survive without qualification
Take any Thornton quote and strike the federal residential credit if it appears, because Section 25D expired for property placed in service after December 31, 2025 and a cash or loan purchase does not receive it.
Section 48E, the commercial credit, survives at 30 percent for third-party owners under leases and power purchase agreements. If a lease or power purchase agreement is on the table, ask what the provider claims and what portion reaches you through the rate, and confirm with a tax advisor.
Then rebuild from full retail net metering, the property tax exemption under Section 39-3-102 C.R.S., the residential energy sales and use tax exemption, Solar*Rewards if you enrol, and the electricity you stop buying.
Ask for that version in writing. An installer working Colorado seriously in 2026 will already have it, and reluctance to produce it is informative in itself.