Incandescent lighting was the brain child of Thomas Edison back in the late 1800's. It served most electrical lighting needs for more than a century but has now taking a back seat to halogen, compact fluorescent and LED (light emitting diode) lighting which are all more efficient. But how much more?
We'll walk you through an example that shows how to evaluate lighting cost over an extended period of time by looking at both energy savings and bulb life.
65 Watt Incandescent Floodlight
In our example, we will use a 150 square foot home office that has four 65 watt incandescent bulbs in recessed lighting fixtures as the baseline. Let's assume the bulbs are used for 8 hours each working day or about 2000 hours per year. To keep the math simple we will use an electricity rate of 10 cents per kilowatt-hour.
To make this scenario fit your home, simply plug in your own numbers to get a realistic picture of how changes to your incandescent lighting will affect your electric bill. Be sure to include the actual hours the lights are on in each room. This will have a big impact on the real energy savings.
Another factor to consider is the actual wattage the bulb draws. If a 65 watt bulb is rated at 130 volts and is used on a 120 volt line it will only draw 60 watts. Bulb life will be extended but illumination will be slightly dimmer.
The best way to measure incandescent lighting power consumption accurately is to use a sample of similar sized bulbs and average the results. Simply use a lamp connected to a plug-in meter and record the readings as each bulb is swapped out.
Now, let's get into the comparison between incandescent lighting, halogens, compact fluorescents and LED's...
1. Upgrade to 50 Watt Halogen Floodlight
Select a halogen bulb that has a comparable illumination rating to the incandescent lighting. In this case the original bulb is rated at 600 lumens and the 50 watt halogen is rated at 575 lumens.
First, determine how many kilowatt-hours will be saved each year:
= 30 KWh per year
At 10 cents per KWh, four 50 watt halogen bulbs will save $12.00 per year.
Bulb life must also be considered. The incandescent bulb is rated at 2000 hours and the halogen at 5000 hours. If we extend our home office example over a ten year period the incandescent bulb replacement cost would be:
Experience has shown that not all bulbs last their full rated life. To compensate for this we will add an additional bulb change every five years for a total of twelve bulb changes over the ten year period. This amounts to $108 which we will use as our incandescent bulb cost baseline.
The halogen bulb we chose is rated at 5000 hours and sells for about $6.20 each in a twin pack. Over ten years, four replacement sets will occur for a total cost of $99.84. Again, experience has shown that not all bulbs last their rated life. To compensate, we'll add a fifth replacement set which brings the total halogen bulb cost to $124.64.
Here's the net savings calculation with halogen bulbs.
Bulb Replacement Savings = $108.00 - $124.64 =-$16.64
Total Savings over 10 Years = $103.36
2. Upgrade to 16 watt Compact Fluorescent (CFL)
The original incandescent bulb which is rated at 600 lumens will be replaced with a 16 watt CFL which has an initial rating of 750 lumens. This rating will fade slightly over time as the bulb ages.
CFL's offer significant energy savings but may take a little time to come up to full illumination, especially in lower temperatures. They also carry a trace of mercury which, over time, may become a landfill issue.
Determine annual kilowatt-hour savings:
= 98 KWh per year
At 10 cents per KWh, four 15 watt CFL bulbs will save $39.20 per year.
Considering the bulb life of the CFL is rated 10,000 hours, it would only need to be replaced twice in a ten year period. However, as with halogens, some CFL's will fail prematurely so we will plan on a total of three bulb replacements.
The CFL we chose sells for $9.97 each. Over ten years, three replacements of four bulbs each would cost a total of $119.64.
Here's the net savings calculations with CFL floodlights:
Bulb Replacement Savings = $108.00 - $119.64 = -$11.64
Total Savings over 10 Years = $380.36
|3. Upgrade to a 9 Watt LED Light
The original 65 watt incandescent lighting with 600 lumens will be replaced with 7 watt LED lighting rated at 560 lumens. Although this may decrease overall the lighting level slightly, LED's are quite bright in the area served by their narrower beam patterns. As long as the distance between recessed lighting fixtures is not too great, illumination differences should be negligible.
Determine the annual kilowatt-hour savings:
At 10 cents per KWh, four 7 watt LED lamps will save $46.40 per year.
The bulb life of the LED is rated at 25,000 hours so only the initial purchase price of $14.99 per bulb needs to be considered. There would be no replacement cost within ten years and some bulb life would still remain after that time. Four bulbs would cost a total of $59.96.
Here are the net savings calculations with the LED lighting:
Bulb Replacement Cost = $108.00 - $59.96 = $48.04
Total Savings over 10 Years = $512.04
Even though LED lamp cost is high when compared to CFL's, halogens or incandescents, their extremely long bulb life delivers total cost savings that is competitive with other options, especially in areas of high usage. LED costs are dropping to where many offer the most energy efficient, cost effective and environmentally friendly option available for incandescent lighting replacement.