Title 24 is California's building standards code, and Part 6 - the Energy Code - is the part that dictates hardware. For pools it means a variable-speed pump, a heater without a continuously burning pilot, a 36-inch length of straight pipe between filter and heater for future solar, and time-switch controls. For a newly built detached ADU it means solar photovoltaics, a heat pump baseline for space and water heating, and HERS verification. The 2025 edition took effect on 1 January 2026. Budget $400 to $900 for the energy calculations and $600 to $1,200 for HERS testing on an ADU.
What Title 24 actually is, and the two compliance paths
Title 24 of the California Code of Regulations is the whole set of building standards. Part 6 is the Energy Code, updated on a three-year cycle - the 2025 edition took effect 1 January 2026. Part 11 is CALGreen, which covers water efficiency, construction waste diversion and indoor air quality.
Compliance runs one of two ways. **Prescriptive** means you meet every listed requirement item by item; simple, but inflexible. **Performance** means an energy consultant models the building in approved software and shows it uses no more energy than a reference design; this is how most ADUs get built, because it lets you trade a better envelope against a bigger window wall.
The paperwork is a set of registered certificates: the CF1R produced at design and submitted with plans, the CF2R signed by the installing contractor, and the CF3R signed by an independent HERS rater. No final inspection without them.
Pro Tip
Get the CF1R done before plan check submittal - it is a plan-check correction that stops everything if it is missing.
Pool and spa equipment: what the code demands
Section 110.4 of the Energy Code, together with the Title 20 appliance efficiency regulations, sets the pool rules.
**Pumps.** Replacement and new residential filtration pumps above roughly 0.7 total horsepower must be variable speed. Budget $1,200 to $2,400 installed. This is a genuine operating saving, not a paper one - running a variable-speed pump at low RPM for longer cycles typically cuts pool pumping electricity by half or better.
**Heaters.** No continuously burning pilot light. An on-off switch mounted outside the heater. Operating instructions posted.
**Piping.** At least 36 inches of straight pipe between the filter and the heater, or dedicated suction and return lines, so solar heating can be added later without cutting into the equipment pad.
**Controls.** Time-switch or automation control on the circulation pump.
A gas heater runs $4,000 to $7,000 installed; a heat pump heater $6,500 to $12,000 and far cheaper to run in coastal climates.
Pro Tip
If you are already replacing the pump, run the solar stub while the pad is open - it costs almost nothing now and thousands later.
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ADUs: which ones must carry solar
This is where money changes hands. A newly constructed detached ADU is a new dwelling, so it falls under the Energy Code's photovoltaic requirement for new low-rise residential buildings. System size is calculated from conditioned floor area and dwelling count, so a 400 to 800 square foot ADU typically lands somewhere around 1 to 2.5 kW - roughly $5,000 to $12,000 installed. Exceptions exist where the roof has genuinely limited solar access, and community solar can substitute in some utility territories.
An ADU created inside existing space - a garage conversion, a basement, part of the house - is treated as an alteration, not new construction, and does not carry the PV mandate. That is one of several reasons a garage conversion at $80,000 to $180,000 undercuts a detached build at $150,000 to $400,000 or more.
Attached ADUs sit in between and depend on how the jurisdiction classifies the work. Confirm classification before you budget.
Pro Tip
If solar is a deal-breaker on budget, price the conversion route before assuming a detached unit is the only option.
Envelope, equipment and what gets tested
For a new ADU the prescriptive package is demanding. Expect high-performance windows in the range of U-0.30 and a solar heat gain coefficient near 0.23, attic or roof deck insulation at R-38 or better in inland climate zones, wall insulation with continuous exterior layers in colder zones, and duct systems inside conditioned space wherever possible.
The 2025 code pushes heat pumps hard. The prescriptive baseline assumes heat pump space heating and heat pump water heating for new single-family construction, with electric-ready provisions where gas equipment is installed instead. A ducted or ductless heat pump for a small ADU runs $6,000 to $14,000; a heat pump water heater $3,500 to $7,000 installed with the required electrical circuit.
A HERS rater then verifies the items the code says must be field-tested: duct leakage, refrigerant charge or fault indication, quality insulation installation and ventilation airflow. That testing is $600 to $1,200.
Pro Tip
Budget the electrical panel upgrade early - a heat pump, a heat pump water heater and an EV circuit often push an older 100-amp service past its limit.
Where projects get caught
Five recurring problems, all avoidable.
**Like-for-like heater swaps.** Replacing a pool heater is permitted work. A unit with a continuously burning pilot will not pass, and neither will an installation with no external on-off switch.
**Undersized panel.** Adding a 400,000 BTU heater, a variable-speed pump and outdoor kitchen circuits to a 100-amp service usually means a service upgrade at $3,500 to $8,000.
**No solar stub.** Missing 36 inches of straight pipe between filter and heater is a correction that means cutting apart a finished equipment pad.
**ADU classified wrong.** Assuming a detached unit is exempt from PV, then finding the requirement at plan check with the budget already fixed.
**Missing certificates.** No registered CF2R or CF3R and there is no final inspection, regardless of how good the work is.
None of these are engineering problems. They are sequencing problems.
Pro Tip
Ask your contractor to name the energy consultant and the HERS rater at contract signing - unassigned, those roles get forgotten.
Who does what, and what the compliance costs
The compliance chain has four named parties, and each has to do their part or the file stalls.
The **energy consultant** runs the model and registers the CF1R. On a small ADU that is $400 to $900; on a whole-house remodel with a large glazing package, $900 to $1,800.
The **designer or architect** carries the assumptions from the CF1R onto the drawings, so window schedules and insulation notes match the model.
The **contractor** installs to those numbers and signs the CF2R. Substituting a window with a different U-factor invalidates the model and forces a re-run.
The **HERS rater** tests and signs the CF3R for $600 to $1,200.
On a pool, the chain is lighter - the equipment schedule on the plans plus field verification at inspection - but the same principle applies: what is installed must match what was submitted.
Pro Tip
Keep the registered certificates with the closing documents; buyers' inspectors ask for them years later.
Final Thoughts
Title 24 is not the obstacle homeowners expect. On a pool it is four hardware decisions, and the variable-speed pump pays for itself in electricity. On an ADU it is a real cost - solar, heat pumps and HERS testing can add $12,000 to $25,000 to a detached unit - which is exactly why it belongs in the budget on day one rather than showing up as a change order at plan check.
Frequently Asked Questions
Yes, for new installations and replacements above roughly 0.7 total horsepower, which covers nearly every residential filtration pump. Budget $1,200 to $2,400 installed. The requirement comes from the Title 20 appliance efficiency regulations working alongside Title 24. Running one at low RPM over longer cycles typically halves pool pumping electricity, so the payback is real rather than theoretical.
No. A newly constructed detached ADU is treated as a new dwelling and carries the photovoltaic requirement, usually landing around 1 to 2.5 kW for a 400 to 800 square foot unit, or $5,000 to $12,000 installed. An ADU created inside existing space, such as a garage conversion, is an alteration and does not trigger the mandate.
The Energy Code requires at least 36 inches of straight pipe between the pool filter and the heater, or dedicated suction and return lines, so a solar heating system can be added later without rebuilding the equipment pad. It costs almost nothing during construction. Retrofitting it into a finished pad means cutting and re-plumbing at $800 to $2,000.
They are the three registered Title 24 compliance documents. The CF1R is the design certificate produced by an energy consultant and submitted with plans. The CF2R is signed by the installing contractor confirming what was actually built. The CF3R is signed by an independent HERS rater after field testing. Missing any of the three blocks final inspection.
