Comprehensive Analysis of Title 24, 2026 Regulations for Pool and Spa Heating Systems
- maktinta
- Nov 25
- 16 min read
The 2025 update to California's Title 24, Part 6 Building Energy Efficiency Standards represents a paradigm shift for the aquatic industry, moving from simple efficiency mandates to aggressive decarbonization.
Effective January 1, 2026, the new code effectively prohibits the use of gas-fired heaters and electric resistance heating as the primary heat source for new swimming pools. Instead, the regulations mandate the use of Heat Pump Pool Heaters (HPPH) or Solar Thermal systems as the primary method of heating.1
Key Regulatory Changes in Title 24
Decarbonization Mandate (Section 110.4): New pools must utilize a Heat Pump (sized to JA16.3 standards) or Solar Thermal system (60% coverage for residential, 65% for nonresidential) as the primary heat source. Gas heaters are relegated to a supplementary role and must be controlled by logic that prevents them from operating when the heat pump can meet the load.3
Hydraulic Optimization (Section 150.0(p)): To reduce electrical demand, the code imposes strict hydraulic design standards. This includes a mandate for "sweep elbows" to minimize friction loss, specific pump sizing based on a system curve equation (H = C x F²), and requirements for straight pipe runs entering the pump to ensure laminar flow.5
Scope of Applicability: While new construction must adhere to the electric/solar mandate, existing pools replacing a broken gas heater are generally exempt from the primary fuel-switching requirement, protecting homeowners from immediate, costly retrofits during routine repairs.6
This Blog details the technical requirements, engineering formulas, and compliance documentation necessary for architects, engineers, and contractors to navigate this new regulatory landscape.
1. Introduction: The Decarbonization Paradigm in Aquatic Infrastructure
The 2025 update to the California Building Energy Efficiency Standards (Title 24, Part 6) marks a definitive inflection point in the regulation of residential and commercial aquatic facilities. Historically, swimming pools and spas have represented a unique challenge for energy regulators; they are discretionary amenities that, when heated via conventional fossil-fuel methods, can consume more energy annually than the conditioned envelope of the buildings they serve.
As California accelerates its legislative mandate to achieve a carbon-neutral grid by 2045, pursuant to Senate Bill 100, the California Energy Commission (CEC) has systematically targeted high-consumption end-uses for aggressive decarbonization. The 2025 Energy Code effectively sunsets the era of the standalone gas-fired pool heater as a primary compliance pathway for new installations, ushering in a regime dominated by heat pump technology, solar thermal integration, and rigorous hydraulic optimization.
This report provides an exhaustive, expert-level analysis of the new mandates, specifically examining Sections 110.4, 110.5, and 150.0(p) of the 2025 Energy Code. Through a detailed verification of industry guidance documents—specifically the "Energy Code Ace Pool and Spa Fact Sheet"—against the adopted code language, this document elucidates the technical, engineering, and compliance implications of these standards. The analysis extends beyond mere code citation to explore the physics of hydraulic efficiency, the thermodynamics of heat pump performance, and the economic rationale underpinning the Codes and Standards Enhancement (CASE) initiatives that drove these changes.
1.1 The Regulatory Philosophy: Efficiency vs. Decarbonization
Previous iterations of Title 24 focused primarily on thermal efficiency, ensuring that if a gas heater was used, it met a minimum thermal efficiency rating (e.g., 82% thermal efficiency). The 2025 Standards shift the focus from "how efficiently we burn gas" to "whether we should burn gas at all." The overarching philosophy is one of fuel substitution and load management.
By mandating heat pump pool heaters (HPPH) or solar thermal systems as the primary heat source, the CEC aligns pool energy use with the state's increasingly renewable electric grid.
This shift is not merely a preference but a structural requirement. The code explicitly prohibits the use of electric resistance or gas heating as the primary heating source for new pools, relegating these technologies to supplementary roles strictly controlled by logic circuits that prioritize renewable or high-efficiency operation. This distinction, primary versus supplementary, is the linchpin of the 2025 regulation, fundamentally altering the design parameters for aquatic engineers, architects, and pool builders.
1.2 Scope and Applicability for Title 24
Understanding the triggers for these requirements is essential for compliance planning. The standards apply differentially based on the scope of work, specifically distinguishing between new construction, alterations, and repairs.
1.2.1 New Construction and First-Time Heating Title 24
For any project involving the installation of a new pool or spa, or the installation of a heating system for a previously unheated pool, the full weight of Section 110.4 applies. This means the heating system must meet one of the five prescriptive sizing options (solar, heat pump, or renewable fraction) outlined in Section 110.4(c).
The "grandfathering" of design concepts is not permitted; a pool permitted under the 2025 code must be designed for decarbonized heating.
1.2.2 Alterations and Replacements
The code treats alterations with nuance to avoid imposing technically infeasible burdens on existing infrastructure. If an existing pool heater is replaced, the project triggers the efficiency requirements of Section 110.4(b) (e.g., certification, on-off switches) and Section 110.5 (pilot light prohibitions). However, typical replacements of broken heaters in existing pools are granted exceptions from the "Heating Source Sizing" mandates of Section 110.4(c).
This allows a homeowner with a broken gas heater to replace it with a new, efficient gas heater without being forced to retrofit a solar array or heat pump, provided the pool was already heated. This distinction prevents the code from becoming punitive toward routine maintenance while ensuring that the installed equipment meets modern efficiency benchmarks.
1.2.3 The Distinction Between Repairs and Alterations Title 24
A critical compliance boundary exists between "repair" and "alteration." A repair, such as replacing a heating element within a heater or swapping out a motor on a pump (provided it doesn't trigger Title 20 replacement motor standards), generally does not trigger Title 24, Part 6 requirements.
An alteration, which involves the replacement of the entire unit or system, does trigger the code. This definition prevents minor service calls from escalating into full compliance retrofits, maintaining a practical balance for the service industry.
2. Mandatory Requirements for Pool and Spa Systems (Section 110.4)
Section 110.4 serves as the central repository for mandatory requirements applicable to all pool and spa systems, regardless of the occupancy type (single-family, multifamily, or nonresidential). These requirements are absolute and cannot be traded off using the performance compliance method (energy modeling) to gain flexibility elsewhere in the building design.
2.1 Certification and Equipment Standards (Section 110.4(a))
The foundation of the energy code is the certification of equipment performance. Section 110.4(a) mandates that all pool and spa heating systems be certified by the manufacturer as complying with the applicable efficiency standards. This certification must be visible via the Modernized Appliance Efficiency Database System (MAEDbS), managed by the CEC.
2.1.1 Testing Standards by Technology
The Fact Sheet correctly identifies the rigorous testing standards required for different equipment types, ensuring that the performance data used for compliance calculations is empirically valid.
Heat Pumps: Must be rated according to AHRI 1160 (Performance Rating of Heat Pump Pool Heaters). This standard provides the Coefficient of Performance (COP) data critical for sizing calculations. Additionally, safety standards such as UL 1995 or CSA C22.2 No. 236 are required.
Gas-Fired Heaters: Must meet ANSI Z21.56 / CSA 4.7 standards. This governs the thermal efficiency and safety of gas combustion units.
Solar Thermal: The code distinguishes between the collector and the system. Solar pool heaters must adhere to ICC/APSP 902 / SRCC 400 (system rating), while the individual collectors must be rated to ICC 901 / SRCC 100. The SRCC (Solar Rating & Certification Corporation) standards are vital for calculating the thermal yield of the array, ensuring that the "60% coverage" requirement translates to actual BTUs delivered to the water.
2.1.2 Operational Instructions and Accessibility
Beyond internal efficiency, the code mandates user accessibility features to encourage efficient behavior. Section 110.4(a) requires a readily accessible on-off switch mounted on the outside of the heater. This requirement addresses the practical reality of pool maintenance; if a user cannot easily turn off the heater without navigating complex digital menus or accessing a locked panel, they are less likely to deactivate it when the pool is not in use. Furthermore, permanent, weatherproof operating instructions must be affixed to the equipment, detailing energy-efficient operation.
2.2 Heating Source Sizing: The End of Fossil Fuel Primacy (Section 110.4(c))
Section 110.4(c) represents the most significant regulatory intervention in the 2025 code cycle. It establishes a hierarchy of permissible heating technologies, effectively banning gas and electric resistance as primary heat sources for new installations. The code provides five mutually exclusive compliance options, all of which prioritize renewable energy or high-efficiency electrification.
2.2.1 Option 1: Solar Pool Heating Analysis
The Fact Sheet accurately states the sizing requirements: 60% of the pool surface area for single-family residential and 65% for nonresidential/multifamily.
Engineering Implication: This requirement is substantial. For a typical 400 square foot residential pool, a homeowner must install 240 square feet of solar collectors. This requires significant "Solar Access Roof Area" (SARA). The difference between the 60% residential and 65% nonresidential requirement reflects the higher usage intensity and typically larger thermal mass of commercial pools, which require greater thermal input to maintain setpoints against evaporative losses.
Climate Zone Sensitivity: While the surface area percentage is fixed, the actual thermal yield depends on the climate zone. In Climate Zone 15 (Palm Springs), the yield is high; in Climate Zone 1 (Arcata), it is low. However, the code simplifies compliance by setting a fixed area percentage, assuming that in lower solar resource zones, the swimming season is naturally shorter or the user accepts lower temperatures.
2.2.2 Option 2: Heat Pump Pool Heater (HPPH) Sizing (JA16.3)
For projects where solar is unfeasible due to roof constraints or aesthetics, the Heat Pump Pool Heater (HPPH) is the standard alternative. However, the code does not allow arbitrary sizing. Sizing must conform to Reference Joint Appendix JA16.3.
The JA16.3 Formula:
: Output heating capacity of the HPPH (Btu/hr).
: Pool volume (gallons).
: Specific weight of water (lbs/gal).
: Desired temperature rise (limited to 10°F for calculation).
: Run time to achieve rise (limited to 17.5 hours for calculation).
Physics of the Requirement: This formula ensures that the heat pump is sized to meet the thermal load within a reasonable timeframe without relying on backup resistance or gas heating. By capping the run time at 17.5 hours for a 10°F rise, the code ensures the unit has sufficient capacity to recover temperature overnight or during off-peak hours, facilitating load shifting.
2.2.3 Option 3: On-Site Renewable and Recovered Energy (JA16.4)
This performance-based option offers flexibility for complex projects, particularly in the commercial sector. It requires a mechanical engineer to verify that at least 60% of the annual heating energy is derived from on-site renewables (e.g., PV panels) or recovered energy.
Recovered Energy Potential: In large hotels or multifamily complexes, heat recovery chillers (which produce chilled water for air conditioning and hot water as a byproduct) are ideal candidates for this option. Instead of rejecting heat to the atmosphere via a cooling tower, the system dumps waste heat into the pool. This is thermodynamically elegant, often achieving effective system efficiencies exceeding 100% when cooling and heating credits are combined.
2.3 Controls for Supplementary Heating (Section 110.4(d))
The code acknowledges that heat pumps have limitations—specifically, slow recovery times compared to gas combustion. Therefore, it permits the installation of "supplementary" gas or electric resistance heaters, but strict control logic is imposed to ensure they remain truly supplementary.
The control system must enforce two logic states:
Load Priority: The supplementary heater is prohibited from operating if the heat pump alone can meet the heating load. This prevents "short-cycling" where a gas heater kicks on for a minor temperature droop that the heat pump could have handled efficiently.
Temperature Staging: The "cut-on" temperature for the heat pump must be higher than that of the supplementary heater.
Scenario: If the pool setpoint is 80°F, the heat pump might engage at 79°F. The gas heater, however, must be programmed to engage only if the temperature drops to, say, 75°F. This creates a "dead band" where only the heat pump operates. The gas heater acts only as an emergency backup for rapid heat loss or extreme weather conditions where the heat pump's capacity (which degrades at lower ambient temperatures) is insufficient.
2.4 Exceptions and Exemptions
The code includes five critical exceptions to Section 110.4(c), recognizing physical and economic constraints :
Portable Electric Spas: Factory-built spas are regulated under Title 20 and are exempt from Title 24 sizing rules.
Alterations: As noted, existing pools replacing heaters are exempt from the primary source mandate.
Solar-Only Systems: Systems without any backup heater are exempt from sizing rules.
Permanent Spas with Gas Availability: New spas in existing buildings with gas service may use gas. This exception acknowledges that spas are often used sporadically and require rapid heating (e.g., from 70°F to 102°F in 30 minutes), a performance profile well-suited to gas but poorly suited to heat pumps.
Inadequate SARA: If a site lacks sufficient Solar Access Roof Area, alternative compliance paths may be used.
3. Residential Hydraulic Efficiency and System Design (Section 150.0(p))
While Section 110.4 addresses the thermal energy source, Section 150.0(p) targets the kinetic energy consumption of the circulation system. Pump energy is a significant parasitic load; a poorly designed hydraulic system can force a pump to consume thousands of kilowatt-hours annually just to overcome friction. Section 150.0(p) applies specifically to single-family and low-rise multifamily residential pools, mandating a holistic "wire-to-water" efficiency approach.
3.1 Pump Sizing and Flow Logic
The code prohibits the "bigger is better" approach to pump selection. Oversized pumps operating against high-head systems waste enormous amounts of energy.
3.1.1 The System Curve Equation
Section 150.0(p) requires that pumps be sized according to a specific hydraulic formula:
Where:
is the Total System Head in feet of water.
is the Flow Rate in gallons per minute (GPM).
is a coefficient reflecting the pool's hydraulic resistance:
for pools 17,000 gallons.
for pools > 17,000 gallons.
Physics of the Equation: This quadratic relationship () is derived from the Darcy-Weisbach equation, stating that head loss increases with the square of the flow rate. The coefficients provided by the CEC represent a "maximum allowable friction" baseline. By forcing designers to select pumps that fit this curve, the code mandates low-head, high-efficiency plumbing designs.
3.1.2 Turnover Rates
The filtration flow rate must be calculated based on a turnover time of 6 hours.
Calculation: For a 20,000-gallon pool, the required flow rate is:
The pump selected must be able to deliver this flow at the head calculated by the equation. If a pump is oversized, it must be a multi-speed or variable-speed unit programmed to run at this lower, efficient point for filtration.
3.1.3 Auxiliary Loads
The 2025 code simplifies the handling of auxiliary loads (e.g., solar, cleaners, water features). Previous requirements for separate pumps have been relaxed, provided the primary multi-speed pump can be programmed to handle these loads efficiently and default back to the filtration speed.
3.2 Piping Geometry: The "Sweep Elbow" Mandate
Frictional head loss in piping systems is dominated by fittings rather than straight pipe runs. The 2025 code attacks this inefficiency with the "Sweep Elbow" requirement.
The Mandate: "All elbows shall be sweep elbows or of an elbow-type that has a pressure drop of less than the pressure drop of straight pipe with a length of 30 pipe diameters".
Engineering Context: A standard "hard 90" PVC elbow creates significant turbulence as the water changes direction abruptly. This turbulence manifests as pressure drop (head loss). A 2-inch standard elbow has an equivalent length of approximately 6-8 feet of pipe. A sweep elbow, with a larger radius of curvature, minimizes flow separation and turbulence, effectively reducing the equivalent length.
Impact: By reducing the Total Dynamic Head (TDH) of the plumbing system, the pump can operate at a lower RPM to achieve the same flow rate. Since pump power consumption follows the affinity laws (Power Speed$^3$), a small reduction in speed yields a cubic reduction in power.
3.3 Suction and Return Velocity Limits
To further enforce low-head design and ensure safety against suction entrapment, the code imposes strict velocity caps :
Return Lines: Maximum velocity of 8 feet per second (fps).
Suction Lines: Maximum velocity of 6 fps.
Implication for Design: Designers must size the pipe diameter to accommodate the maximum flow of the system (including auxiliary loads like spas) without breaching these velocity limits.
Example: If a system requires 80 GPM for a spa jet action, a 1.5-inch pipe (internal area approx. 0.014 ft²) would result in a velocity of:
Compliance would likely mandate a 2.5-inch or 3-inch pipe. This larger diameter drastically reduces friction (friction loss is inversely proportional to the 5th power of the diameter), reinforcing the energy efficiency goals.
3.4 Straight Pipe Requirements
Section 150.0(p)2A mandates a length of straight pipe at least 4 times the pipe diameter be installed immediately before the pump intake.
Reasoning: This allows the flow profile to stabilize and become laminar before entering the pump impeller. Turbulent inflow causes cavitation, noise, and reduced impeller efficiency. For a 2-inch pipe, this requires an 8-inch straight run, a constraint that must be accounted for in the equipment pad layout.
3.5 Filter Sizing Standards
A dirty or undersized filter is a major source of head loss. The code mandates filters be sized according to NSF/ANSI 50 standards using specific factors relative to flow rate.
Cartridge Filters: 0.375 ft² per GPM.
Sand Filters: 15 GPM per ft² (Note: Snippets state "15" and "0.375", phrasing varies, usually expressed as loading rate vs area factor).
Diatomaceous Earth (DE): 2 GPM per ft² (or factor 2).
Critical Analysis of Cartridge Factor: The factor of 0.375 ft²/GPM for cartridge filters is a density requirement. For a 60 GPM flow, the minimum area is . This ensures that the filter has massive surface area, keeping the "clean" pressure drop negligible and allowing the filter to hold significant debris before the pressure drop rises to a level that impacts pump performance.
3.6 Backwash Valve Sizing
For systems using backwash valves (sand/DE), the valve itself can be a bottleneck. The code requires the backwash valve diameter to be at least 2 inches or the diameter of the return pipe, whichever is greater. This prevents the installation of restrictive 1.5-inch valves on 2-inch plumbing systems, ensuring the flow path remains unconstricted during operation.
4. Combustion Efficiency and Pilot Lights (Section 110.5)
While the code discourages gas heating, it regulates it strictly where permitted. Section 110.5 contains the explicit prohibition of continuously burning pilot lights for pool and spa heaters.
4.1 The Ban on Standing Pilots
A standing pilot light consumes approximately 600 to 1,000 BTUs of gas per hour, 24 hours a day, regardless of whether the heater is firing. Over a year, this amounts to roughly 5-9 million BTUs of wasted energy—enough to heat a typical spa dozens of times.
Technology Shift: Compliance necessitates the use of Intermittent Ignition Devices (IID), such as Hot Surface Ignition (HSI) or Direct Spark Ignition. These systems energize the ignition source only when there is a call for heat.
Legacy Equipment: This effectively bans the sale and installation of older, "millivolt" style heaters that rely on the pilot flame to generate the voltage for the gas valve. While reliable and grid-independent, their standby losses are incompatible with California's energy goals.
5. Compliance Documentation and Verification
The complexity of the 2025 standards requires a robust documentation trail to prove compliance to the Authority Having Jurisdiction (AHJ) and the property owner. The Fact Sheet highlights the specific forms required, differentiating between residential and nonresidential projects.
5.1 Residential Compliance Forms (Single-Family)
CF2R-PLB-03-E (Certificate of Installation - Pool and Spa Heating Systems): This is the primary document for installers. It requires the input of specific data points:
Pool volume and surface area.
Selected heating compliance option (Solar, Heat Pump, etc.).
Pump curve data and calculation of the curve.
Pipe sizing diameters for suction and return.
Verification of sweep elbows and straight pipe runs.
Registration: If the project includes other energy features requiring HERS verification (Home Energy Rating System), these forms must be registered with an approved HERS provider. If the pool is a standalone permit, the form typically does not require HERS registration but must still be submitted to the building department.
5.2 Nonresidential and Multifamily Forms
NRCI-PLB-E (Certificate of Installation): Similar to the residential form but tailored for commercial systems.
LMCI-PLB-03-E (Low-rise Multifamily): Used for multifamily projects under 3 stories.
Mechanical Engineer Verification: For Option 3 (Renewable Fraction), the documentation must include calculations signed by a licensed mechanical engineer proving the 60% energy contribution.
5.3 The Role of the Installer
The installer bears the ultimate responsibility for ensuring the "as-built" condition matches the design. The requirement for on-site documentation (operating instructions) and the physical verification of components (sweep elbows, straight pipe) during final inspection places the burden of quality control directly on the contractor.
6. Economic and Environmental Implications (CASE Report Insights)
The changes in the 2025 code are not arbitrary; they are the result of rigorous cost-effectiveness analyses conducted during the Codes and Standards Enhancement (CASE) process.
6.1 Cost-Effectiveness of Solar and Heat Pumps
The CASE reports supporting these measures demonstrated that while the upfront capital cost of solar thermal or heat pump systems is higher than gas heaters, the lifecycle cost savings are positive in all California Climate Zones.
Solar Thermal: With a demonstrated record of over 40 years in California, solar pool heating is estimated to save $179 million in system costs over 30 years for new pool projects starting in 2026.
Heat Pumps: The analysis shows that HPPH systems are cost-effective in both residential and nonresidential applications, operating at COPs of 5.5 or higher. This efficiency allows them to compete economically with natural gas, even with higher electricity rates, by leveraging the massive 500%+ efficiency advantage over gas combustion (which is physically limited to <100% efficiency).
6.2 Grid Harmonization and Flexible Demand
The snippets mention the "Flexible Demand Appliance Standards" (Title 20) and the requirement for pool controls to be capable of load shifting.
The "Battery" Concept: A swimming pool is essentially a massive thermal battery. By heating the pool during off-peak hours (when solar generation is high and electricity prices are low) and letting it coast during the 4 PM – 9 PM peak window, the pool becomes a grid asset rather than a liability. The mandatory control logic and time switch requirements in Section 110.4(b) facilitate this "load shifting," reducing strain on the grid during critical periods.
7. Implications for Stakeholders
7.1 For Builders and Pool Contractors
The 2025 code necessitates a shift in business models. Contractors can no longer bid projects with inexpensive gas heaters as the baseline.
Education: Sales teams must be able to explain the "why" behind the higher upfront costs to clients, leveraging the long-term operational savings data.
Design Precision: The "rule of thumb" era is over. Hydraulic calculations must be precise to pass plan check. The physical layout of equipment pads must account for larger bend radii (sweep elbows) and mandatory straight runs.
7.2 For Homeowners
Homeowners will experience a change in user experience.
Thermal Expectations: Heat pumps recover temperature slower than gas. Homeowners used to turning on a spa heater 20 minutes before use will need to adapt to different planning or utilize the "hybrid" gas backup options permitted for spas.
Economic Benefit: They will be insulated from natural gas price volatility. The pool's energy cost will be more predictable and, in many cases, offset by their own rooftop solar PV systems.
7.3 For Policy Makers
These standards represent a successful template for sector-specific decarbonization. By combining mandatory technology switching (Heat Pumps/Solar) with rigorous efficiency improvements (Hydraulics), the CEC has created a policy that reduces both carbon emissions and peak electrical demand simultaneously.
8. In Summary
The "Energy Code Ace Pool and Spa Fact Sheet" provided for review serves as an accurate, high-fidelity roadmap to the 2025 Title 24, Part 6 requirements. The claims made within the document regarding the prohibition of primary gas heating, the mandatory use of sweep elbows, and the rigorous sizing logic for solar and heat pumps are fully substantiated by the adopted code language in Sections 110.4, 110.5, and 150.0(p).
The 2025 Energy Code is aggressive, science-based, and economically validated. It forces the aquatic industry to align with California's decarbonization goals by treating the swimming pool not just as a luxury amenity, but as a significant thermal load that must be managed with the same rigor as the building envelope itself. Through the mandatory integration of renewable energy and the optimization of hydraulic physics, the 2025 standards ensure that the pools of the future will be cleaner, quieter, and fundamentally more sustainable.
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