Own or lease a building in Denver between 5,000 and 24,999 sq ft? The City updated how small buildings can comply with Energize Denver on September 1, and some deadlines fall on December 31, 2026. Watch the 6-minute walkthrough, then use the summary below to find your deadline and your options.
Who is affected
Energize Denver sets energy-efficiency requirements by building size. Per the City's September 30, 2026 presentation, buildings of 5,000 to 24,999 sq ft (about 7,500 buildings) must upgrade their lighting to LED, use on-site or off-site renewable energy to meet 20% of annual site energy use, or comply through an Alternate Compliance Option (ACO). Buildings of 25,000 sq ft and larger (about 3,000 buildings) have separate energy-performance requirements based on building type; owners should confirm their building’s assigned timeline rather than assume a universal 2032 deadline.
Your due date depends on your size
The City extended the small building deadlines. Find your size band:
| Building size | Due date |
|---|---|
| 20,000–24,999 sq ft | December 31, 2026 |
| 15,000–19,999 sq ft | December 31, 2027 |
| 10,000–14,999 sq ft | December 31, 2028 |
| 5,000–9,999 sq ft | December 31, 2029 |
The pressure is on the first group. As of September 29, 2026, 644 buildings in the 20,000–24,999 sq ft group were still not in compliance, with the deadline about three months away. This is a dated compliance-status snapshot, not a count of buildings that had already missed that deadline. All small buildings were sent letters and emails with their new due dates.
Three ways to comply
A building of 5,000 to 24,999 sq ft must meet one of these by its deadline:
- Lighting: 90% of lighting load, or 97% of fixtures, are LED.
- Renewables: 20% of annual site energy use.
- An Alternate Compliance Option (ACO).
What changed in the ACOs on September 1
- Simplified: no more pre-applications.
- Residential Condominium ACO: the renewable energy requirement is removed.
- 15% Energy Use Reduction ACO: an energy audit is no longer required.
- New: Electrification ACO.
- New: Restaurant ACO.
Residential Condominium ACO
Condos can meet the lighting and occupancy-sensor requirements in shared common spaces only, rather than the whole building. You need a third-party lighting professional, verified 100% LED lighting in common spaces, and occupancy sensors where the Denver Building and Fire Code allows. No pre-application or approval is required: complete the work first, then submit your documentation.
15% Energy Use Reduction ACO
Work with a contractor who has examined your annual utility bills and implemented upgrades estimated to cut annual energy use by 15%. Measures that count include insulation, air sealing and windows, a building automation system, and cold-climate heat pumps. Setpoint and schedule changes, new fossil fuel equipment, and routine maintenance and repairs do not count. Work completed after November 22, 2021 could count. You submit the contractor's proposal showing the estimated reduction, the original invoice, and the final permit inspection document with "permit finaled" status.
Electrification ACO (new)
Replace one piece of central heating equipment that is currently fossil fueled and nearing the end of its system life. The heat pump must meet the current Denver Energy Code at the time of permitting, and one rooftop unit or air handling unit is enough. Projects since November 22, 2021 count. Submit the quote or spec sheet, the original invoice, a signed confirmation of completed work, and the final permit inspection document.
Restaurant ACO (new)
Choose one route. Option 1 is to complete all seven kitchen efficiency measures: set the water heater to 140°F, install faucet aerators, install low-flow pre-rinse spray valves, install smart thermostats with off-hour setback, complete a refrigeration tune-up in the past 12 months, train staff to turn off equipment during off hours, and retrofit one EC motor. Option 2 is to electrify one major piece of fossil-fueled kitchen equipment: a fryer, griddle, combination oven, convection oven, steam cooker, or the kitchen's domestic water heater. The replacement must be ENERGY STAR rated where applicable. Equipment not on the list needs pre-approval.
Strip malls and multi-tenant buildings
Commercial multi-tenant buildings have flexibility to complete multiple pathways and consolidate them into one submission. Different tenants can complete different options, but there is one option per tenant space, every tenant space must be accounted for, and there is one submission per building. The Help Desk can help you consolidate the submission.
If you need more time
The City lists possible reasons for a timeline extension, including delays in budget approval for capital upgrades, a planned major renovation, Landmark Preservation Commission review, financial distress, high vacancy rates, a change of building ownership, lease restrictions, and Xcel Energy interconnection delays. An application needs the reason, the pathway or ACO you intend to use, when you intend to implement it, and supporting documentation.
Next steps
- Claim your building.
- Confirm your deadline.
- Determine your status.
- Choose your pathway.
These are the four steps on the City’s small building page, part of the Energize Denver Navigation Center launched in September.
Help is available. The Energize Denver Help Desk is open Monday to Friday, 8am to 5pm, as currently listed in the City’s Navigation Center, at (844) 536-4528. For buildings of 5,000 to 24,999 sq ft, email [email protected]. An in-person help session runs Wednesday, October 7, 2026, 1:00–5:00 pm at Hadley Branch Library, 1890 S Grove St, Denver, CO 80219. No need to register.
Why this matters beyond Denver
Denver's approach, with size-based deadlines, prescriptive pathways and flexible alternate options, is one of the more detailed building performance standards in the US. The separate requirements for larger buildings are also worth following if you work on performance standards in other cities.
By Chris Mbori. This is an independent explainer based on the City of Denver's Energize Denver presentation (Sept 30, 2026). It is not an official City publication and not legal advice. Slide images are from the City's presentation and credited to the City and County of Denver. Always verify requirements and deadlines with the Energize Denver Help Desk.
Official sources and useful links
- Energize Denver: small-building deadlines and next steps.
- Small-building compliance pathways.
- Alternate Compliance Options.
- Small-building technical guidance, version 4.0, September 1, 2026. Consult this for complete specifications and documentation requirements.
- October 7, 2026: Hadley Branch Library help session.
Official web resources checked October 1, 2026. The slide statistics retain their September 29, 2026 snapshot date.