Boulder Pool Heater Rules: Heat Pumps and Gas

Boulder pool and spa heating rules

Boulder County and the City of Boulder set related but different rules for heated pools and spas. Strata is taking consultation requests for pool and spa heat pumps now. We quote after a site visit. We install and service pool heat pumps, including cold-climate inverter models and standard models.

Boulder County building code section B26 states, "Heated pools of 200 sq ft or more must use solar thermal or non-fossil heating, or offset their energy with on-site renewables." A pool heat pump uses electricity to move heat rather than burn fuel. That places it within the county's non-fossil heating path.

B26 also states, "Spas must be offset unless they are CEC Title 20 listed and under 64 sq ft." This spa exception differs from the county pool rule. We review the pool or spa size, equipment plan, and site details before recommending a hot tub heat pump or pool heat pump.

The City of Boulder uses a separate renewable energy offset form. Its rule applies to both pools and spas, while B26 gives distinct language for pools and spas. The first step is identifying which local rule applies to the property and equipment plan.

Where Boulder County rule B26 applies

The Boulder County rule comes from Boulder County, Swimming Pools, Spas and Hot Tubs, building code section B26. It applies the stated pool requirement at 200 sq ft or more. A heat pump avoids fossil fuel combustion, while a gas pool heater must use solar thermal or a renewable offset to meet that county requirement.

For spas, the county rule is framed around an offset. The stated exception is limited to spas that are CEC Title 20 listed and under 64 sq ft. A hot tub heater based on a heat pump still needs a site review, because the B26 spa wording is about the offset and exception.

Boulder County has 142,809 homes, Census figures show. Its 69.9% gas heat share is higher than Denver County's 61.5%. That difference matters for pool equipment decisions because many properties already have gas equipment, yet county B26 sets a different path for a heated pool or spa project.

Boulder County's median year built is 1986, close to El Paso County's 1988. Each property still needs its own electrical check. A pool heat pump needs dedicated equipment capacity, regardless of the age of the home or its existing gas equipment.

The City of Boulder offset form

Inside the City of Boulder, the City of Boulder Renewable Energy Offset Requirements Form says, "Pool and spa energy must be offset with on-site renewables." The city form also says heat pumps count on the city offset worksheet for seasonal pools. The city requirement is an energy-offset requirement, rather than the county's separate pool and spa wording.

We confirm with the city how the worksheet credits your heat pump before you apply. That step matters because the city worksheet recognizes a heat pump for seasonal pools. We do not assume the city credit without confirming the worksheet treatment for the planned equipment.

A gas pool heater does not get the heat-pump treatment on the city worksheet. To comply, it needs a renewable offset. Boulder rules accept solar thermal or a renewable offset. A pool heat pump changes the compliance approach because it moves heat with electricity instead of relying on gas combustion.

This distinction changes the planning conversation before pool heater installation. A heat pump has a city worksheet role for a seasonal pool. A gas heater follows the renewable offset path instead. We confirm that path with the city before the application.

How a pool heat pump fits Boulder rules

A heat pump fits Boulder County B26 as non-fossil heating for a heated pool of 200 sq ft or more. In the City of Boulder, heat pumps count on the offset worksheet for seasonal pools. We check which jurisdiction governs the address, then confirm the city worksheet treatment before the application moves forward.

Gas capacity drops roughly 4% per 1,000 ft, about 20% at Front Range altitude. A heat pump has no combustion derate. That makes equipment output at local elevation an important difference between an electric pool heater and a gas unit, even before code compliance is reviewed.

Standard models have limits in cooler weather. Many standard pool heat pumps stop at 40F and lose output below 50F. Cold-climate inverter models with reverse-cycle defrost are rated to run down to 23F, 5F or, for some models, -4F. A cold-climate unit stretches the swim season to roughly April through October and can heat a spa year-round.

Equipment output also changes with dry air. Pool heat pump ratings assume 80F air at 80% humidity. Front Range summer afternoons often run 15 to 25% humidity, so real output is lower. We size the pool heat pump for dry air rather than relying on rating conditions alone.

Running cost and controls for Boulder pools

The cost case depends on operation, code, and season length. Gas at $1.00 per therm in an 83% efficient pool heater costs $1.20 per useful therm. At a COP of 5 in a warm afternoon, a heat pump costs $0.46 at the off-peak base rate, or $0.64 with riders, per useful therm.

At a COP of 4 in typical conditions, the figures are $0.58 and $0.81. At a COP of 3 in cool or very dry air, they are $0.77 and $1.07. At a COP of 2.5 on a 35F shoulder night, the figures are $0.80 and about $1.00. These figures use off-peak base rates and add about 3 cents per kWh of riders.

Colorado Public Utilities Commission Time of Use Rates list Xcel Energy's residential peak from 5 to 9 pm on weekdays, at 21.3 cents per kWh in summer. Every other hour, weekends included, is off-peak at 7.9 cents per kWh in summer and 6.8 cents October through May. Scheduled to stay off during peak, a heat pump runs about 10 to 60% cheaper than gas.

These are base rates, not an all-in bill. We check the numbers against your own Xcel bill before we quote. The pool heat pump cost case relies on time-of-use scheduling, dry-air sizing, the local rule, and the desired swim season.

Sizing pool and spa equipment on the Front Range

We heat mostly between 9 am and 5 pm, when air is warmest and the heat pump is most efficient. The pool coasts through the 5 to 9 pm peak, losing well under 1F with a cover. It tops up overnight only when needed. Without time-of-use scheduling, most savings disappear, so controls are part of pool heater installation.

A 140,000 BTU pool heat pump needs a 50 A, 240 V circuit. We check panel capacity at the site visit and plan load management where the panel is tight. A pool over 20,000 gallons may need two units and two circuits. These checks set the equipment plan before we quote.

Raising a 20,000 gallon pool 10F takes about 6 hours on a 400,000 BTU gas heater and about 15 hours on a heat pump. A heat pump holds temperature rather than heats on demand. That makes it a strong fit for a scheduled pool temperature plan rather than a fast recovery request.

People use spas in the evening, inside the 5 to 9 pm peak. We preheat the spa by 5 pm and it coasts on an insulated cover. Elsewhere on the Front Range, we check the local rule at the site visit along with dry-air sizing, panel capacity, and the required circuits. Request a consultation. We visit, size the unit for dry air, and quote.

Pool heat pumps by location

Questions we hear

What does Boulder County B26 require for heated pools?

Boulder County B26 says, "Heated pools of 200 sq ft or more must use solar thermal or non-fossil heating, or offset their energy with on-site renewables." A pool heat pump moves heat with electricity rather than burning fuel, so it fits the non-fossil heating path. A gas pool heater needs solar thermal or a renewable offset.

What does Boulder County require for spas?

The county rule says, "Spas must be offset unless they are CEC Title 20 listed and under 64 sq ft." The spa wording differs from the pool requirement. We review the spa size, the equipment plan, and the stated exception at the site visit before planning a hot tub heat pump installation.

How is the City of Boulder rule different from Boulder County B26?

The City of Boulder form says pool and spa energy must be offset with on-site renewables. It also says heat pumps count on the city offset worksheet for seasonal pools. County B26 instead states a non-fossil heating option for heated pools of 200 sq ft or more, plus separate spa language. We confirm the city worksheet credit first.

Will a pool heat pump work in Front Range weather?

Cold-climate inverter models with reverse-cycle defrost are rated to run down to 23F, 5F or, for some models, -4F. They stretch the swim season to roughly April through October and can heat a spa year-round. Standard models often stop at 40F and lose output below 50F, so equipment selection matters.

Why do you schedule pool heating outside peak hours?

Xcel Energy's residential peak is 5 to 9 pm on weekdays, at 21.3 cents per kWh in summer. Off-peak summer power is 7.9 cents per kWh. We heat mostly between 9 am and 5 pm, then let a covered pool coast through peak. For spas, we preheat by 5 pm and use an insulated cover.

Boulder County and City of Boulder rules for pool and spa heaters