Brighten rooms while trimming daytime lighting energy use. Model HVAC effects, costs, and incentives easily. See payback, ROI, and charts in seconds right here.
| Scenario | Skylights | Watts | Reduction | Rate | Upfront | Net Savings | Payback |
|---|---|---|---|---|---|---|---|
| Baseline | 2 × 0.80 m² | 300 | 35% | $0.18 | $1,450 | $210 / yr | 6.90 yrs |
| High daylight | 3 × 0.90 m² | 420 | 40% | $0.20 | $2,100 | $420 / yr | 5.00 yrs |
| Low cost retrofit | 1 × 0.70 m² | 180 | 30% | $0.16 | $650 | $120 / yr | 5.42 yrs |
Upgraded skylights increase usable natural light, letting fixtures stay dimmed or off during peak daytime hours. This calculator converts your baseline daytime wattage and daylight hours into annual kilowatt-hours, then applies an expected reduction percentage and an optional controls gain to reflect dimming sensors and schedules.
Glazing can change both heat loss and solar gain. For heating, the tool estimates conduction savings from the difference between old and new U-values, scaled by skylight area and heating degree days. For cooling, it estimates reduced solar load from the change in SHGC and a site solar factor, then divides by the cooling COP to convert thermal load to electric use.
Energy savings are only part of project value. Enter equipment and installation costs separately so you can compare product choices and labor scenarios. Rebates reduce cost directly, while tax credits are calculated as a percentage of eligible costs with an optional cap. Annual maintenance is subtracted from savings to keep the net figure realistic.
Simple payback divides net upfront cost by annual net savings and is useful for quick screening, but it ignores time value. NPV discounts each year’s net savings using your selected discount rate across the analysis period. A positive NPV indicates the upgrade returns more value than your assumed alternative use of funds.
Use the component breakdown to sanity-check assumptions: lighting, heating, and cooling should align with your building and climate. If you have measured HVAC impacts, switch to manual kWh entries for more reliable totals. Compare scenarios by adjusting daylight hours, tariffs, and incentive levels, then export CSV or PDF for stakeholders. Consider running a conservative case with smaller reductions and higher maintenance, and an optimistic case with stronger controls. The gap between those cases shows risk. When payback is long, focus on NPV, comfort, and quality benefits that are not captured in bills.
Start with a walkthrough of daytime spaces. Compare current fixture usage to expected daylight coverage after the upgrade. Many projects begin with 20–40% reduction, then refine using light meters or sensor trend data.
That can happen if solar gain drops more than heat-loss improvements. Enter negative heating savings in manual mode or adjust U-value and SHGC inputs to match the selected glazing and shading strategy.
Use estimate for early planning when you only know glazing performance and climate data. Use manual when you have audit results, utility analysis, or measured HVAC kWh impacts from similar installations.
Rebates reduce the upfront cost directly. Tax credits are calculated as a percentage of eligible equipment and installation costs, limited by the cap you enter, then subtracted from the remaining cost.
NPV includes the time value of money and counts all savings across the full analysis period. A project can recover slowly but still generate strong discounted value over 10–20 years.
It estimates emissions avoided from the electricity portion of savings using your emission factor. If heating uses gas or another fuel, those emissions are not included unless you convert them into kWh-equivalent separately.
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.