Lighting Control Calculator

This calculator looks up the ASHRAE 90.1 Table 9.5.1 lighting power density (LPD) limit for your building type -- ten preset values ranging from 0.19 W/sq ft for a parking garage up to 1.06 W/sq ft for retail -- and compares it against your installed or budgeted wattage. Code LPD limit (W/sq ft) depends entirely on Building type (1-10) and never on Floor area (sq ft), Lighting zones, or Daylight zones, all three of which have zero effect on the limit itself. If you leave Installed lighting (W) at its 0 default, the calculator assumes you're designing to exactly the code maximum, so Actual LPD (W/sq ft) equals Code LPD limit (W/sq ft) and Code Compliant reads true by construction; entering a real installed wattage is what makes the compliance check meaningful.

Floor area (sq ft) has a direct, always-positive effect on Max allowed watts (a larger floor area allows proportionally more total watts at the same LPD limit), but again, no effect on the LPD limit or ratio itself. Lighting zones drives Occupancy sensors and Control relays one-for-one (each zone gets one sensor and one relay), while Daylight zones drives Daylight sensors one-for-one -- these are simple per-zone device counts, not a lighting layout or fixture-level design. Estimated annual savings blends a fixed 25% assumption for occupancy-sensor savings with a 35% assumption for daylight-dimming savings, weighted by what fraction of zones have daylight access (capped at 100% of zones, since Daylight zones and Lighting zones are entered independently and Daylight zones could otherwise be entered larger than Lighting zones itself), and assumes 3,000 operating hours per year and $0.12/kWh -- both fixed constants, not inputs you can adjust here.