Boiler repair in Denver: costs, safety checks and when to replace

How much does boiler repair cost?

The figures below come from HomeAdvisor's boiler repair cost guide, updated in June 2026. They include parts and labor; emergency, after-hours, weekend and holiday visits cost more.

HomeAdvisor lists standard boiler labor at a flat $150 to $300 or $75 to $130 per hour. It also notes that annual service contracts often lower the per-visit cost.

What are the common signs of boiler trouble?

• Some rooms or zones cold, others warm. Often a stuck zone valve, a failing circulator pump or air in the system.
• Banging, gurgling or kettling noises. Can indicate trapped air, low water or scale buildup on the heat exchanger.
• Pressure gauge reading far above or below normal, or water dripping from the pressure relief valve. A waterlogged expansion tank is a frequent cause.
• Boiler cycling on and off quickly or failing to light, which can point to an ignitor, sensor or control fault.
• Visible water under the boiler or around radiators and baseboard.
• Soot, a yellow flame or a carbon monoxide alarm. Treat any of these as a safety issue, not a comfort issue.

If the boiler stops working in freezing weather, pipes in the heating loop and the rest of the house can freeze. Our emergency checklist covers what to do first.

What carbon monoxide precautions apply?

A fuel-burning boiler that is poorly vented or poorly maintained can produce carbon monoxide. The U.S. Consumer Product Safety Commission says more than 200 people in the United States die each year from accidental non-fire carbon monoxide poisoning tied to consumer products. It recommends battery-operated or battery-backup CO alarms on every level of the home and outside sleeping areas, ideally interconnected so that when one sounds they all sound. Symptoms include headache, dizziness, weakness, nausea, vomiting, sleepiness and confusion; if you suspect CO, get outside and call 911.

Colorado also has a CO alarm law. According to the National Conference of State Legislatures, Colorado Revised Statutes 38-45-101 to 106 require an operational CO alarm near each sleeping room in homes with a fuel-burning heater or appliance, a fireplace or an attached garage when they are sold or transferred, with a similar requirement for new construction.

Repair or replace: how efficient is your boiler?

Boiler efficiency is rated as AFUE, annual fuel utilization efficiency. ENERGY STAR certifies gas boilers at 90 percent AFUE or higher and oil boilers at 87 percent or higher, which it says is about 6 percent and 1 percent more efficient than the federal standard, respectively. ENERGY STAR estimates a certified gas boiler can save about $780 over its lifetime. The current ENERGY STAR boiler specification took effect in January 2024.

If you replace an older non-condensing boiler, check utility incentives. Xcel Energy's 2024 Colorado residential rebate summary listed $250 for a boiler of 95 percent AFUE or higher replacing a non-condensing boiler, and $350 for the same upgrade paired with a side-arm water heater. Programs change yearly, so confirm current offers on Xcel's rebates page. A side-arm (indirect) tank heats domestic water from the boiler; our water heater guide compares other options.

Does boiler work need a permit in Denver?

Denver handles boilers under its own Boiler and A/C permit type. For single-family homes and duplexes, the city's quick permit page lists boilers, radiant heating and potable hot water systems over 200,000 BTU as eligible work. The company you hire normally pulls the permit and schedules the inspection.

Who should you hire for boiler repair?

Boilers sit at the overlap of plumbing and heating, so ask each company which licenses its technicians hold and which Denver contractor license covers the job. You can check a Colorado plumbing license in the DORA lookup and contact Denver Contractor Licensing at (720) 865-2770 to confirm a company's city license. Ask whether the visit includes a combustion and venting check, a CO test and an expansion tank check, and get the price for any parts in writing before work starts. Our boiler maintenance guide explains what an annual service should include.

We are an independent guide, not a heating or plumbing company. You can email a request to dispatch@denverplumberpros.com through the contact page.