Lighting Energy Savings Form
Existing fixture watts = old lamp watts + old ballast or driver watts.
New fixture watts = new lamp watts + new ballast or driver watts.
Connected load saved = fixture count × watts saved per fixture ÷ 1000.
Annual kWh saved = connected load saved × hours per day × days per year × cooling adjustment multiplier.
Annual energy savings = annual kWh saved × electricity rate.
Annual demand savings = connected load saved × peak factor × demand charge × 12.
Simple payback = net project cost ÷ total annual savings.
Net present value = present value of yearly savings − net project cost.
How to Use This Calculator
- Enter the number of lighting fixtures in the project.
- Add the old lamp watts and old ballast or driver watts.
- Add the proposed lamp watts and new driver watts.
- Enter daily hours, yearly operating days, and utility charges.
- Add fixture cost, labor cost, rebates, and maintenance savings.
- Use cooling adjustment when lower lamp heat affects cooling load.
- Click Calculate Savings to view savings, payback, and carbon reduction.
- Download the result as CSV or PDF for records.
Example Data Table
| Project |
Fixtures |
Old W |
New W |
Hours/Year |
Rate |
Estimated kWh Saved |
Estimated Annual Savings |
| Office troffer upgrade |
100 |
72 |
27 |
2600 |
$0.14 |
11,700 |
$2,424.00 |
| Parking area retrofit |
40 |
440 |
165 |
4380 |
$0.16 |
48,180 |
$10,372.00 |
| Classroom lamp change |
60 |
37 |
16 |
1600 |
$0.12 |
2,016 |
$482.40 |
Lighting Energy Planning
Lighting upgrades save power by reducing watts at each fixture. The calculator compares the existing load with a proposed replacement load. It then connects the watt difference with annual operating hours. This gives yearly kilowatt hours saved. The tool also estimates demand savings, carbon reduction, project payback, and net value.
Why watts matter
A lamp may look small, yet many fixtures run for long periods. A ten watt cut across one hundred fixtures removes one kilowatt from the connected load. When those lights run ten hours daily, savings build quickly. Driver or ballast watts also matter. Older systems may use hidden power above the lamp rating. Entering those watts improves the estimate.
Operating hours and rates
Hours drive the result. A warehouse, clinic, school, or parking area may use lights differently. The calculator uses hours per day and days per year. It multiplies them to find annual runtime. The electricity rate converts energy into money. A demand charge can add savings when lower lighting load reduces billed peak power. Use the coincidence factor to estimate how much of the lighting load appears during utility peak periods.
Project cost view
A good retrofit decision needs more than energy savings. Fixture price, labor, and rebates affect payback. The tool subtracts rebates from the installed cost. It then divides net cost by yearly savings. This shows simple payback. It also calculates lifetime savings and discounted value. These numbers help compare projects with different prices and lifetimes.
Physics behind savings
Electrical power is measured in watts. Energy is power used over time. One kilowatt running for one hour equals one kilowatt hour. Lighting efficiency improves when the same task uses fewer watts. Some projects also lower cooling demand, because efficient lamps release less heat indoors. The cooling adjustment lets you add that interaction when it applies.
Using the results
Treat the output as a planning estimate. Use measured wattage when available. Confirm fixture counts with a site walk. Check utility bills for the correct rate. Include maintenance savings only when lamp life, lift rental, or service time will truly change. A careful input set creates a stronger business case and better upgrade plan. Decide before spending capital or scheduling crews safely.
FAQs
1. What does this lighting calculator estimate?
It estimates connected load reduction, annual kWh savings, utility cost savings, demand savings, project cost, payback, lifetime savings, net present value, and carbon reduction.
2. Should ballast watts be included?
Yes. Ballasts and drivers can use extra power. Add them to the lamp watts for a more realistic connected load and energy savings estimate.
3. What is the peak coincidence factor?
It shows how much lighting load is active during the utility peak. Use 1 for full coincidence. Use a lower value when lights are partly off during peak billing periods.
4. How is annual kWh savings calculated?
The calculator subtracts new lighting load from old lighting load. It then multiplies the saved kilowatts by yearly operating hours and cooling adjustment.
5. What does cooling adjustment mean?
Efficient lights release less heat. In cooled spaces, this may reduce cooling energy. Enter a positive percent when you want to include that extra savings effect.
6. Can this calculator show negative savings?
Yes. If the proposed lighting uses more power or costs more to operate, the result can be negative. That helps identify poor retrofit choices.
7. Is simple payback the same as net present value?
No. Simple payback shows years to recover cost. Net present value discounts future savings and compares them against today’s project cost.
8. Can I use local currency?
Yes. Enter your preferred currency symbol in the first field. The calculator uses that symbol in cost, savings, rebate, and payback results.