What Is a Title 24 Lighting Power Allowance?
It is the maximum installed lighting power a space is permitted, calculated per primary function area rather than for the building as a whole. Exceed the total and the design does not comply on the prescriptive route.
How the total is built
The Area Category Method assigns a lighting power density to each primary function area in the project — office, lobby, corridor, sales floor, warehouse and so on — and the permitted total is the sum across those areas. It is usable for any permit situation including tenant improvements, which is why most commercial projects are assessed on it.
Because the allowance follows function, the mix of spaces decides the budget. Two fit-outs of identical area can have very different allowances if one is mostly open office and the other is mostly storage and circulation.
Why the room schedule matters as much as the fittings
A plan that labels rooms by number rather than by use has to be interpreted before it can be calculated, and an area read as storage when it is really a sales floor carries a different density. Naming the use of each space on the drawing is the cheapest accuracy improvement available on a commercial lighting submittal.
Power Adjustment Factors
Specific measures earn credit against the allowance. The recognised set includes daylight continuous dimming plus off, occupant sensors in offices at one sensor per under 125 square feet, occupant sensors at one per 126 to 250 square feet, institutional tuning for daylit and non-daylit areas, demand response, clerestory fenestration, horizontal slats and light shelves.
These are earned by installing and documenting the measure, not by claiming it. Where a daylighting feature is credited it has to appear in the construction documents and be verified in the field by acceptance test, so a credit taken in the calculation and value engineered out of the build becomes a compliance failure.
What to do when a design is over
Three levers, in rough order of cost: more efficient fittings, fewer fittings, or reallocating power between general and accent lighting. The performance path is the fourth option, which lets a lighting overage be offset elsewhere in the building — but it has to be modelled rather than asserted.