Daylight harvesting: code-required in window-zone spaces.
Daylight harvesting systems automatically dim or shut off artificial lighting when natural daylight provides sufficient illumination.
By Steven Lockhart · Reviewed by Alex Towery, C-10 #989290
Updated 2026-06-16
Daylight harvesting requirements: Title 24 requires daylight harvesting in commercial spaces with qualifying window exposure (specific criteria for window area, room depth, and orientation). Implementation via photosensors that measure ambient light and signal lighting controls to dim proportionally. Per-zone scope $200-$800 depending on sensor count and control sophistication. Energy savings 15-40% in daylight-qualifying spaces — meaningful in spaces with substantial daylight access.
01How daylight harvesting works.
Photosensors mounted near windows or in daylight-influenced zones measure ambient light levels. Control system receives sensor readings and adjusts connected lighting circuit dimming proportionally — full output when daylight is low (early morning, evening, overcast), reduced output as daylight contributes more. Properly tuned systems are imperceptible to occupants; lights smoothly adjust without distracting changes.
Implementation varies in sophistication. Simple daylight harvesting: one photosensor per zone, simple proportional dimming control. Advanced daylight harvesting: multiple sensors per zone with weighted averaging, closed-loop control accounting for occupant lighting preferences, integration with networked lighting management. More sophisticated systems deliver larger savings but cost more.
02Three implementation approaches.
Standalone daylight sensors
Per-zone photosensor with simple dimming control. Lowest cost approach ($200-$400 per zone). Works well for spaces with single window orientation and clear daylight zone boundaries. Most common retrofit approach.
Networked daylight harvesting
Integrated with networked lighting control system. Multiple sensors per zone, sophisticated control logic, integration with occupancy and schedule. Higher cost ($400-$800 per zone) but better performance and easier ongoing adjustment.
Manual override capability
Required by Title 24 — occupants must be able to override automatic dimming. Implementation via wall switches that temporarily override the automatic control. Important detail often missed in cheaper implementations.
03Common Marin daylight harvesting scenarios.
Office spaces with windows: typically 30-50% of office area qualifies as daylight zone (within 1.5x window head height from window wall). Daylight harvesting in these zones delivers 20-35% lighting energy savings. Standard scope for modern office TI in Marin.
Retail with significant glazing: storefront-facing display areas often have substantial daylight. Daylight harvesting balances natural and artificial light for consistent merchandise visibility. Application varies by retailer brand standards — some prioritize consistent artificial lighting regardless of daylight.
Common questions.
Do all spaces need daylight harvesting?
No — Title 24 requires daylight harvesting only in spaces with qualifying window exposure (specific criteria for window area, room geometry, orientation). Most enclosed spaces with windows qualify; interior spaces without daylight access don't need daylight harvesting controls.
Will I notice the dimming?
Properly tuned daylight harvesting is essentially imperceptible. Lights smoothly adjust as daylight changes without distracting jumps. Poorly tuned systems can produce noticeable dimming events; tuning during commissioning resolves.
How much does daylight harvesting cost?
Standalone implementation: $200-$400 per zone added to standard lighting control scope. Networked implementation: $400-$800 per zone. Cost varies with zone count and integration sophistication. Payback through energy savings typically 2-5 years for qualifying spaces.
How do you handle pricing — flat fee or hourly?
Both, depending on scope. Routine service calls and predictable scope (panel replacement, EV charger install, transfer switch install, fixture replacement) are flat-fee quoted up front. Diagnostic visits and emergency scope are hourly because we don't know what we'll find. Either way, you get a written quote before work starts on anything significant, and we don't proceed beyond the quote without your sign-off.
How quickly can you schedule?
Depends on scope and season. Emergency dispatch: same-day across Marin County (1-3 hours business hours, 1-4 hours after-hours). Same-day standard service: 3-6 hours from call when capacity allows; otherwise next business day. Scheduled service work: 1-3 weeks typical. Larger projects requiring permits and PG&E coordination: 4-12 weeks depending on scope. We're upfront about timeline at the quote stage.
What warranty do you offer on work?
Our standard residential warranty: 2 years on labor, manufacturer warranty on parts (varies by product — typically 1-10 years). Major installs (panels, generators, EV chargers) often have longer manufacturer warranties (5-10 years). If there's an issue with our work in the warranty period, we come back and fix it at no cost. We also stand behind work past warranty — repeat customers and referrals matter more than a transactional fix.
Are you licensed and insured?
Yes. California State License Board C-10 Electrical Contractor #989290, in good standing. Carry general liability insurance and workers' compensation insurance as required by California law. Bondable on projects requiring it. Happy to provide proof of insurance to clients or property managers on request. License lookup: cslb.ca.gov.
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Family-run, C-10 #989290, 20+ years in the trade. Honest scoping, fair pricing, work that lasts.