By Marcelle Dibrell

For decades, the gas heater has been the unquestioned choice for attached spas. Turn it on, walk away, come back in about an hour, and the water is hot. That reliability — and speed — has defined homeowner expectations.

So when California contractors, service techs, and homeowners hear that their state is moving away from gas in favor of electricity, it’s reasonable to ask: Is electric heating technology truly ready to replace gas for on-demand spa applications?

Let’s begin with what’s happening in California: Beginning January 1, 2026, under California’s updated Title 24 energy code, gas pool and spa heaters may no longer serve as the primary heat source in many newly constructed pools and first-time heater installations. For permits filed on or after that date, the primary heat source must be electric (such as a heat pump) or solar-based. Gas heaters may still be installed, but only as secondary or supplemental systems paired with a compliant primary heat source.

Meanwhile:

• Some California municipalities have limited installation of new

Stephen Staples of Chlor-Free Company in Simi Valley, California takes home the Grand Prize of $20K at the 48th Annual Western Pool & Spa Show show held Feb. 12-14, 2026 in Long Beach, California. See story page 6. natural gas infrastructure in certain new construction projects.

•The California Energy Commission (CEC) continues tightening appliance efficiency standards.

• The California Air Resources Board (CARB) regulates low-NOx emissions, influencing gas heater design and compliance requirements.

It’s important to clarify that there is no statewide ban on residential gas pool or spa heaters. Existing heaters remain legal, and replacements are generally permitted in retrofit situations.

Still, the directional shift toward electrification in new construction is clear.

Policy preference, however, does not automatically equal performance equivalence.

That’s where math matters. Electrification policy is largely motivated by the goal of reducing emissions. The simplified climate argument is that as the electric grid becomes cleaner, shifting from on-site combustion to electricity will lower the overall carbon impact .

Contractors and frequent spa users tend to focus on something different:

• Heat-up speed.

• Reliability.

• Real operating cost.

• Suitability for repeated, ondemand use. So let’s set rhetoric aside and look strictly at physics, performance, and cost.

How Much Heat Does a Typical Spa Need?

Consider a realistic attached spa located in a Sunbelt state:

• Roughly 7 feet across

• About 3 feet deep

• Built-in bench seating After seating displacement, a working volume of approximately 640 gallons is reasonable.

Assume a conservative winter scenario:

• Starting temperature: 60°F

• Target temperature: 104°F

• Temperature rise: 44°F Water requires 8.34 BTU per gallon per degree Fahrenheit.

640 × 44 × 8.34 ≈ 234,000 BTU That is the base energy required to raise the spa to soaking temperature — not including shell absorption, plumbing losses, or wind effects.

Gas Heater Performance

A typical residential gas heater:

• 400,000 BTU/hour input

• ~84% thermal efficiency Output: 400,000 × 0.84 ≈ 336,000 BTU/hour Theoretical heat-up: 234,000 ÷ 336,000 ≈ 0.70 hours ≈ 42 minutes But real-world performance — accounting for shell mass, piping losses, and exposure — typically lands gas heaters at: 60–75 minutes.

That matches the lived experience of spa owners who heat on demand several nights per week.

Gas heaters were engineered specifically for high-output, rapid temperature rise applications.

Heat Pump Performance in Sunbelt Climates

Modern inverter-driven heat pumps from manufacturers such as Pentair, Raypak, Hayward, and Fluidra are often rated at 120,000–140,000 BTU/ hour — but those ratings are achieved at 80°F air temperature.

At 60°F air — more typical of winter evenings in California or Arizona — output commonly drops to 100,000–115,000 BTU/hour.

Using 110,000 BTU/hour: 234,000 ÷ 110,000 ≈ 2.13 hours But real-world performance — accounting for shell mass, piping losses, and exposure — typically lands heat pumps at: 2 to 2 ½ hours.

That is meaningfully slower than gas.

And this is where design intent matters.

Swimming pool heat pumps were engineered primarily for steady, longduration heating, where efficiency over time is the goal. They excel at achieving temperature gradually and maintaining it economically in mild climates.

They were not originally designed for rapid, high-output, repeated ondemand spa heating cycles.

That does not mean they cannot perform the task.

It means they perform it differently. Operating Cost Comparison (California Rates) Assumptions:

• 2.5 hours of heat-up (heat pump scenario).

• 1 hour soak time.

• Electricity: $0.40/kWh.

• Natural gas: $2.20 per therm.

Heat Pump

Total heat required: 234,000 BTU Assume COP = 4.0 at 60°F air. COP (Coefficient of Performance) measures efficiency. A COP of 4 means the heat pump moves four units of heat into the water for every one unit of electrical energy consumed.

Energy required: 234,000 ÷ 4 = 58,500 BTU Convert to kWh: 58,500 ÷ 3,412 ≈ 17.1 kWh 1 BTU = 3,412 kWh Cost: 17.1 × $0.40 ≈ $6.84 Including soak time, we estimate that a heat pump costs approximately $7.50 per session

Gas

Required input: 234,000 ÷ 0.84 ≈ 279,000 BTU Convert to therms: 2.79 therms Cost: 2.79 × $2.20 ≈ $6.14 Including soak time, we estimate that a gas heater costs approximately $6.75 per session Cost Per Use (CA Rates) Gas: ≈ $6.75 Heat Pump: ≈ $7.50 At current California utility averages, gas is slightly cheaper per spontaneous use.

But in lower-electric-rate regions — or when offset by rooftop solar — the math can shift.

Note that operating cost depends heavily on local rates and usage patterns.

Installation Costs

Typical installed ranges:

• 400K gas heater: $4,500–$7,000.

• High-end heat pump: $4,000– $6,500.

Gas line extensions or meter upgrades can add cost in electrificationfocused neighborhoods.

But on a unit-for-unit basis, the equipment pricing is comparable.

Cold Climate Reality

Most pool heat pumps operate down to about 40°F air temperature. Below that:

• Output drops.

• Defrost cycles increase.

• Efficiency declines.

• Some units shut off.

At 35°F, output may fall to roughly half rated capacity. And below freezing, practicality declines rapidly.

In cold climates, gas remains the only realistic solution for rapid winter spa heating; that is a function of thermodynamics.

The Practical Comparison

In mild Sunbelt climates:

Gas

• ~1 hour heat-up.

• ~$6–7 per session.

• Consistent performance.

Heat Pump

• ~2–2.5-hour heat-up.

• ~$7–8 per session (CA averages).

• Performance tied to ai r temperature.

Heat pumps are not instant. They are not universally cheaper. They are not optimized for repeated, lastminute heating cycles.

However, they are effective in mild climates when:

• Heating is planned in advance.

• Solar offsets electricity.

• Emissions reduction is prioritized.

• Gas infrastructure is limited. For a homeowner who heats their spa three or four nights a week — often deciding an hour before use — speed and responsiveness matter.

For a homeowner comfortable scheduling heat-up earlier in the evening, the trade-offs may be acceptable.

This is not a debate about whether heat pumps “work,” because they do.

It is a question of application fit. Gas heaters remain unmatched for rapid, high-output, on-demand heating.

Heat pumps offer high efficiency and lower emissions in appropriate climates — but with slower temperature rise.

The honest decision comes down to one question: How quickly does the homeowner want heat — and how often?

Answer that clearly, and the correct equipment choice should become obvious.