Outdoor Lighting Zones Explained

California assigns every location a lighting zone from LZ0 to LZ4, based on how much light the surroundings already have. The zone sets your outdoor lighting power allowance — and no area in California is currently LZ4.

Five zones, by surrounding ambient light

LZ0 — zero ambient. Undeveloped areas with essentially no artificial lighting.
LZ1 — low ambient. Developed portions of government designated parks, recreation areas and wildlife preserves.
LZ2 — moderate ambient. Rural areas.
LZ3 — moderately high ambient. Urban areas.
LZ4 — high ambient. Maximum artificial lighting.

The zones are based on U.S. Census Bureau data rather than assigned building by building, which is why the zone is a property of the location and not a choice.

No area in California is LZ4

LZ4 describes the most intensely lit environments — a Times Square sort of place. Currently no areas within California fall under LZ4.

That is worth knowing before anyone reaches for it. The zone exists in the table, and in practice a Californian project is working in LZ0 through LZ3. If a calculation has been built on LZ4 allowances, it is built on allowances the project cannot have.

The allowance follows the zone

Lighting zone determines the outdoor lighting power allowance, lowest in LZ0 and highest in LZ4. The reasoning is about contrast rather than about generosity: in a genuinely dark area the eye adapts and very little light is needed to see well, while in a brightly lit urban setting the same fitting reads as dim against its surroundings.

So the same car park needs materially more power to be usable in LZ3 than in LZ1 — and would be over-lit and intrusive in LZ1 at LZ3 levels.

Why LZ1 is the one to watch

LZ1 covers developed parts of parks, recreation areas and wildlife preserves. A project next to or inside one of those can find itself in a much tighter zone than the nearest town, with an allowance that will not support a conventional lighting scheme.

This is not only an energy matter — dark-sky and habitat considerations are the reason those areas are classified low — but the effect on the compliance calculation is the same. It has to be established from the location rather than assumed from the character of the development.

Establish the zone before designing the scheme

Because the allowance is layered — general hardscape, plus outdoor sales lot and frontage allowances where they apply — the zone sets the base every other allowance builds on. A design laid out first and checked afterwards can be a long way over on a site that turns out to be LZ1 or LZ2.