Rooftop unit replacement planning guide for Denver commercial buildings

When an RTU is due for replacement

Energize Denver's service life chart, built from ASHRAE data, lists rooftop air conditioners at 20 years and gas furnace sections at 20 years. Plenty of units run longer and some fail sooner, depending on maintenance, hail exposure and how hard they are cycled. Age alone is a planning signal, not a verdict. These are the conditions that usually push a unit from repair to replacement:

• A failed compressor or cracked heat exchanger on a unit past the middle of its life.
• Repeated repairs that add up to a meaningful share of a new unit within a year or two.
• A refrigerant circuit that keeps leaking, especially on older R-22 equipment where refrigerant is scarce and costly.
• Controls that cannot be integrated, an economizer that no longer works, or capacity that no longer matches the tenant.
• An Energize Denver target that the existing equipment cannot help the building reach.

Start with a unit-by-unit survey

Most surprises on lift day come from skipping the survey. For each unit we record:

• Nameplate data: model, serial, age, tonnage, heat type and input, voltage and phase.
• Curb dimensions and condition, and the roof membrane and flashing around it.
• Gas connection size and routing, electrical disconnect and circuit, condensate path.
• Economizer type and condition, controls and thermostat or building automation points.
• Ductwork connections, return and supply openings, and space served.
• Crane access: where the crane can set up, lift radius and obstacles such as power lines and trees.

The survey becomes the bid scope. It also tells the owner which units can wait, which should go now, and whether grouping several units into one crane day makes sense.

Choosing the replacement equipment

Like-for-like is the default, but it is not always the best answer. The main choices for a Denver building:

Altitude

At about 5,280 ft, air in Denver is roughly 15% less dense than at sea level. That lowers delivered airflow mass and gas combustion air, so equipment must be selected and set up with the manufacturer's high-altitude data. Gas-fired sections typically need high-altitude orifices or derating per the installation instructions. A unit sized from a sea-level catalog can come up short.

Refrigerant transition

Under the EPA Technology Transitions rule, new air conditioning and heat pump equipment has moved to lower global warming potential refrigerants, mostly A2L refrigerants such as R-454B and R-32. Deadlines have been amended more than once, most recently in a May 2026 final rule affecting residential and light commercial equipment built before 2025. For owners, the practical effect is that replacement units will usually run a different refrigerant from the old one, so line sets, service tools and technician training must match. Confirm the refrigerant and the applicable compliance date for the specific unit at bid.

Hail and controls

Hail guards are worth pricing on exposed roofs along the Front Range. A changeout is also the cheapest time to add a working economizer and networked controls, which often save more energy than the efficiency difference between unit models.

Curbs, structure and the roof

If the new unit matches the old curb, the swap is simplest. If not, a curb adapter avoids cutting the roof. Heavier units, especially heat pumps with larger coils or units with added accessories, can exceed the original structural design, so we flag weight changes for review by the owner's engineer. When the curb or flashing is in poor condition, we coordinate with the roofing contractor so the roof warranty is protected and the new unit is not set on a failing curb.

Crane, street use and lift day

When the crane or its outriggers sit in a Denver street, sidewalk or parking lane, the lift needs a Street Occupancy permit from the Department of Transportation and Infrastructure. The city's FAQ says the normal minimum review time is 5 days, a traffic control plan is required for every closure, and sidewalk closures are required for cranes and boom trucks. Lifts from a private parking lot avoid the street permit but still need a lift plan and a clear set-up area. Suburban cities have their own right-of-way rules.

Lift day usually starts early or on a weekend. The old unit is disconnected and picked, the curb or adapter is prepared, the new unit is set and connected, and startup follows. Grouping several units into one crane day spreads crane and mobilization cost and keeps tenant disruption to a single event.

Permits and code

Replacing an RTU requires a mechanical permit, and the electrical and gas work must be inspected. Denver's energy code page for existing commercial buildings lists replacement gas-fired warm-air furnaces and unitary air conditioners serving a heated space among the equipment subject to partial electrification provisions. A gas-heat packaged unit can fall into that group. The city's guidance on how and when that applies has changed over time, and our guide on Energize Denver HVAC upgrades walks through what each source says. Confirm the current requirement with the city before ordering gas-heat equipment, and price a heat pump alternative so you are not choosing under deadline.

Budget and schedule

Typical range, exact pricing after plan review or site walk. Per-unit pricing depends on tonnage, heat type, curb, structure, controls and crane requirements.

Schedule planning tips: replace in spring or fall when a unit being down for a day carries the least comfort risk; order equipment once the survey and options are approved, because lead times vary by manufacturer and season; and book the crane and street permit only once delivery is confirmed.

Rebates

Xcel Energy's business HVAC-R program has historically offered prescriptive rebates for rooftop units, dual fuel rooftop units, heat pumps and VRF, plus custom rebates that require preapproval before purchase. The most recent public Colorado listing sheet we could find is dated 2023, so amounts may have changed. As of October 14, 2026, treat any rebate figure as subject to change and confirm the current amounts and requirements with Xcel before buying equipment. Denver's building decarbonization rebates can stack with Xcel programs for eligible electric equipment.

Planning checklist

1. Survey every unit. Nameplate, condition, curb, utilities, controls and crane access.
2. Decide unit by unit. Repair, replace now, or plan for a later crane day.
3. Select equipment. Gas, heat pump or dual fuel, sized with altitude data.
4. Check structure and roof. Weight changes, curb fit, roofer coordination.
5. Confirm code and incentives. Mechanical permit, energy code status, Xcel and city rebates before purchase.
6. Plan the lift. Crane, street occupancy permit if needed, tenant notices.
7. Start up and document. Commissioning, controls and records for maintenance and benchmarking.

See our rooftop unit replacement service, maintenance agreements that keep new units in warranty shape, and 24/7 emergency response when a unit fails before its planned date.