How the Numbers Are Calculated
All calculations in the Outdoorlink Efficiency Calculator are derived from the NOAA Solar Position Algorithm combined with your specific timer, inventory, and rate inputs. No external API calls are made — everything runs locally in your browser.
Sunrise & Sunset
Uses the NOAA Solar Position Algorithm. For each month's mid-point day, the model computes: fractional year, equation of time, solar declination, hour angle, solar noon, sunrise, and sunset. The zenith angle of 90.833° accounts for atmospheric refraction and the sun's apparent diameter. DST-aware: applies the Summer UTC offset for March–October and the Winter UTC offset for November–February, matching local clock time year-round.
Timer Waste
If Timer ON is before sunset: (Sunset − Timer ON) × 24 = wasted hours per day. If Timer ON is after sunset, waste is zero. Multiply by days in month × timer faces for inventory hours, then × kW × rate for cost.
Photocell Excess
Photocell-controlled faces stay lit from sunset to sunrise. Excess hours measure the time from Timer OFF to next sunrise: ((1 − Timer OFF fraction) + Sunrise fraction) × 24. This captures hours photocell faces burn that timer faces do not.
Unsold Face Burn
Unsold faces are split proportionally by inventory mix (timer % vs. photocell %). Timer burn = Timer ON→OFF daily hours. Photocell burn = average sunset→sunrise hours across 12 months. Adjusted by Unsold Face Efficiency % to reflect real-world management practices.
Energy Conversion
kWh = Hours × (Wattage ÷ 1000)
Cost = kWh × Utility Rate
All wattage is the total per-face value entered in inputs.
Total Annual Savings
Sum of Solar Waste savings (timer + photocell illumination waste eliminated) plus Unsold Burn savings (energy saved by properly managing unsold inventory illumination). Reflects the total efficiency opportunity across the entire fleet.
CO₂ Emissions Avoided
Wasted energy is converted to carbon using a grid factor of 0.386 kg CO₂ / kWh. Metric tons: kWh × 0.386 ÷ 1000. Pounds: kWh × 0.386 × 2.205. The same factor is used across both calculators.