CORE’s 10 kW line and what it means for sizing
CORE offers net metering to residential members whose systems are 10 kW AC or smaller and whose expected production doesn’t exceed 200% of annual use. A member with a larger system can still interconnect, but every kilowatt-hour exported is credited monthly at CORE’s avoided cost — $0.04616 per kWh from May 2026, recalculated annually.
Many Douglas County homes are large and use enough power to justify more than 10 kW of panels. For those, the choice is between staying at or below 10 kW AC for net metering, or going larger and pairing the system with a battery so more of the solar is used at home instead of exported for a fraction of its retail value.
Xcel in Highlands Ranch and Lone Tree
Highlands Ranch, an unincorporated community, and most of Lone Tree are on Xcel Energy. Xcel customers face a 5–9 pm weekday on-peak window with prices about 2.7 times off-peak. Territory lines near Lone Tree and Castle Pines are irregular, so check your bill.
Mountain View Electric also serves a small area of southeastern Douglas County.
Permits: county, towns and CORE paperwork
Castle Rock and Parker have their own building divisions. Highlands Ranch and the rest of unincorporated Douglas County go through the Douglas County Building Division, which since January 10, 2022 has required a signed CORE application form in every PV permit packet where CORE is the utility.
The county requires structural engineering for PV roof framing — dead, snow and wind loads plus attachment hardware — and a building permit when roof trusses need reinforcement. Where no reinforcement is needed, the permit proceeds with electrical inspections only.
HOAs across the county
A large share of Douglas County homes are in master-planned communities with HOAs. Colorado law (C.R.S. 38-30-168) voids covenants that prohibit solar and caps what an HOA can require: its restrictions can’t add more than 10% to cost or reduce performance by more than 10%, and an application not acted on within 60 days is deemed approved.
We prepare the architectural submittal with the plans the HOA needs, which usually makes approval routine.
Wildfire, hail and the Palmer Divide
The western county borders Pike National Forest, and the 2002 Hayman Fire burned into southwestern Douglas County. Homes in Sedalia, Perry Park and along the foothills are in wildland-urban interface where outage resilience matters.
Castle Rock and Parker get Front Range hail, and the county’s southern edge rises onto the Palmer Divide, where snow is heavier. Racking and module choices account for both.
FAQ
Questions we hear
Why do Douglas County installers keep mentioning 10 kW?
Because CORE net-meters home systems only up to 10 kW AC. Larger systems still work, but their exports are credited at CORE’s avoided cost — about 4.6 cents per kWh as of May 2026.
Is Highlands Ranch on CORE or Xcel?
Mostly Xcel Energy. Most of the rest of the county, including Castle Rock and Parker, is CORE.
What extra paperwork does Douglas County require for CORE customers?
Since January 10, 2022, PV permit packets for CORE-served properties must include a signed CORE application form.
Can my HOA in Castle Pines stop me from installing solar?
No. Colorado law voids covenants that prohibit solar. An HOA can impose reasonable restrictions, but they can’t add more than 10% to cost or reduce performance by more than 10%, and it must act on your application within 60 days.
Who issues solar permits in Castle Rock?
The Town of Castle Rock’s building division. The county handles unincorporated areas like Highlands Ranch.
What happens to my excess solar in CORE territory at year end?
For net-metered systems, CORE credits excess generation monthly and settles the annual excess at its avoided cost. For systems over 10 kW AC, exports are credited monthly at avoided cost.