Turn daylight into measurable energy and cost savings. Model controls, tariffs, incentives, and investment costs. Download reports, compare scenarios, and justify upgrades easily today.
| Scenario | Baseline (kWh/yr) | Saved (kWh/yr) | Annual savings | Payback (yrs) |
|---|---|---|---|---|
| Office, basic controls | 17,550 | 3,159 | $673.85 | 17.81 |
| Retail, strong daylight | 51,840 | 16,252 | $3,125.33 | 6.88 |
| School, moderate schedule | 24,480 | 3,277 | $658.82 | 25.80 |
Useful daylight is rarely constant across a workday. Perimeter zones can see strong morning peaks, mid‑day stability, and late afternoon declines. A realistic daylit fraction should reflect occupied hours, blind use, and sky conditions. For many offices, 0.30–0.55 is common, while retail with skylights may exceed 0.60 during open hours.
Effectiveness captures how much electric lighting is reduced when daylight is present. Dimming systems that are commissioned well often deliver 40–70% reduction in the controlled fixtures. Performance falls when sensors are mislocated, setpoints drift, or occupants override scenes. Pairing daylight response with occupancy sensing can further improve realized savings.
Annual energy saved equals baseline lighting energy multiplied by the daylit fraction, control effectiveness, and occupancy factor. Multiply saved kilowatt‑hours by the electricity rate to estimate bill reduction. If your rate is time‑varying, use an effective blended price, or run separate scenarios for peak and off‑peak hours to bracket outcomes. Many commercial sites use 0.12–0.25 per kWh, so identical kWh savings can produce different paybacks.
Simple payback divides net initial cost by annual savings, making it easy to screen projects. Net present value discounts future savings and is better for comparing alternatives with different lifetimes. Internal rate of return summarizes project yield; many organizations target double‑digit IRR for controls upgrades, especially when incentives reduce upfront cost. When escalation is assumed, document the annual percentage and align it with budgeting guidance.
Small changes in inputs can shift results. Test daylight fraction ±0.10, electricity rate ±20%, and effectiveness ±15% to see the range. Document assumptions, confirm fixture wattage during audits, and plan commissioning. Ongoing verification, such as monthly trend reviews, helps sustain savings and protect business cases. A staged rollout helps: pilot one zone, collect meter data for four weeks, then scale settings building‑wide while training staff on overrides and dashboards monthly.
Perimeter zones, atriums, and areas under skylights usually benefit most because daylight reaches work surfaces consistently. Spaces with predictable schedules and limited manual overrides typically produce higher, more stable savings.
Start with operating hours, then estimate the portion when daylight is adequate for tasks. Use site observations, lighting studies, or daylight simulation. Adjust for blinds, overhangs, and local weather patterns.
Occupancy factor accounts for real-world usage. Meeting rooms, classrooms, and shared areas are often empty for long periods. Combining daylight response with occupancy assumptions avoids overstating savings.
Include sensors, control hardware, wiring, programming, commissioning, and any ceiling or electrical rework. If calibration is required, include it as an annual cost or reduced savings.
Apply incentives as a direct reduction to the upfront investment, which improves payback, NPV, and IRR. Confirm eligibility rules and payment timing, since delays can affect cashflow.
No. Reduced lighting can lower cooling loads and sometimes increase heating needs. For larger projects, model HVAC interactions separately or add a savings line item when estimates are reliable.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.