Calculator Inputs
Example Data Table
Sample scenarios to show typical outcomes. Replace these values with your own for accurate results.
| Scenario | Bulbs | Halogen (W) | LED (W) | Hours/day | Rate/kWh | Annual kWh saved | Annual energy saved |
|---|---|---|---|---|---|---|---|
| Living room | 6 | 50 | 7 | 3 | 0.20 | 282.3 | 56.46 |
| Kitchen | 10 | 35 | 5 | 4 | 0.18 | 626.6 | 112.79 |
| Outdoor fixtures | 8 | 60 | 9 | 8 | 0.22 | 1210.3 | 266.26 |
Formula Used
- Days per year = 365 × (days per week ÷ 7)
- Annual hours = hours per day × days per year
- Annual energy (kWh) = (watts ÷ 1000) × annual hours × number of bulbs
- Annual energy cost = annual kWh × electricity rate
- Energy savings = halogen kWh − LED kWh
- Cost savings (energy) = halogen energy cost − LED energy cost
- Bulb sets needed = ceil(total hours ÷ lifetime hours)
- Total ownership = energy cost + optional bulb purchases + optional labor
- Simple payback = extra upfront ÷ annual energy cost savings
How to Use This Calculator
- Enter how many bulbs you want to compare.
- Type the wattage for halogen and the LED alternative.
- Set typical hours per day and days per week used.
- Add your electricity rate from the latest bill.
- Optionally include bulb prices, lifetimes, and labor.
- Click Calculate Savings to view results above.
- Download a CSV or PDF report for sharing.
Professional Guide
1) Why lighting upgrades matter
Lighting is a small device with a big footprint. A single high‑use fixture can run thousands of hours each year, so wattage differences translate into measurable energy and bill changes. Homewide upgrades can reduce evening demand when many lamps run.
2) Understanding wattage and brightness
Wattage is power draw, not brightness. When comparing halogen to LED, match light output in lumens or an equivalent package rating, then compare watts for a fair savings estimate. Color temperature and beam angle also affect perceived brightness, especially in task areas and spotlights.
3) How usage patterns drive cost
Daily hours and weekly days set your operating time. Long runtime spaces such as kitchens, hallways, and outdoor security lights usually produce the fastest savings because electricity costs scale directly with hours. If your schedule varies, use an average across weekdays and weekends.
4) Annual energy math in practice
Annual kWh equals watts divided by 1,000, multiplied by yearly hours, multiplied by the number of bulbs. The calculator applies this to both technologies, then subtracts to show energy reduction. This makes it easy to see how a small watt difference becomes a large annual total.
5) Total ownership beyond electricity
Energy is only one piece. Purchase price, lamp lifetime, and replacement labor can shift the economics. Halogen lamps typically need more changeouts, adding cost and inconvenience over multi‑year periods. LEDs often last longer, reduce ladder trips, and can lower downtime for businesses and rentals.
6) Payback and decision thresholds
Simple payback compares extra upfront LED cost to yearly energy savings. Short payback supports rapid retrofit plans, while longer payback may still make sense if you value fewer replacements and steadier performance. Consider bulk pricing, rebates, and installation access, because they can move payback.
7) Carbon impact estimation
If you enter an emissions factor, the calculator converts saved kWh into avoided CO₂. This helps quantify environmental benefit alongside monetary savings, which is useful for reporting and household targets. When the grid becomes cleaner over time, real CO₂ savings may be lower than a constant factor suggests.
8) Tips for accurate inputs
Use the electricity rate from your bill, include taxes only if they are part of your per‑kWh charge, and choose realistic lifetimes. For mixed use rooms, average hours across seasons to reduce overestimation. If you are unsure, run a best‑case and worst‑case scenario to bracket your likely savings.
FAQs
How do I choose an LED equivalent for my halogen?
Match lumens and beam angle first. Then check wattage, color temperature, and base type. If the LED is dimmable, confirm compatibility with your dimmer to avoid flicker.
What if my electricity bill shows multiple rates?
Use the average price per kWh for your usage tier, or run two scenarios. For time‑of‑use plans, model peak hours with the higher rate to estimate worst‑case costs.
Does the calculator include bulb replacements automatically?
Yes. It estimates how many bulb sets are needed from lifetime hours and total operating hours. Enable purchase costs and optional labor to include replacement expenses in total ownership.
Why is my payback shown as N/A?
Payback becomes N/A when LEDs do not save energy annually, when extra upfront cost is zero or negative, or when usage hours are too low to offset the purchase difference.
How accurate is the CO₂ savings number?
It depends on the emissions factor you enter. Use a factor that matches your grid or supplier. Treat the result as an estimate because grid intensity can change over time.
Should I include taxes and fees in the electricity rate?
Include them only if they are charged per kWh. If your bill has fixed monthly fees, keep them out of the rate because the lighting change will not alter those charges.
Can this tool compare different numbers of bulbs in each type?
This version assumes the same bulb count for both technologies to compare like‑for‑like. If you are changing fixture quantity, adjust the bulb count and rerun separate scenarios.