I set out to see if an LED bulb would save money compared to a CFL bulb and, if so, when would it start saving me money.
Care must be taken when buying LED bulbs since some of these bulbs use just as much or even more electricity than the same equivalent CFL bulb. In this case, with the higher cost to purchase and the equal or higher cost to operate, the LED bulb will never pay for itself compared to the CFL bulb.
These calculations were for 40W-equivalent LED (6W) and CFL (10W) bulbs.
NOTE: In all the equations that follow, I will be using the standard computer math symbols:
+ is the plus sign, add
– is the minus sign, subtract
* is the multiplication sign, multiply
/ is the divide sign, divide
I am also using a $0.10 per KWhr cost for this calculation. If your electricity costs are higher the payback time will be shorter. I have a spreadsheet that can be used to calculate the payback for any LED, CFL bulbs. I also included the old standard incandescent bulb for comparison. This spreadsheet will be on my KE3FL web site and may also be hosted here at solidsignal.com.
The spreadsheet: [ATTACH]789[/ATTACH]
The ecosmart LED bulb uses 6W and claims a 22.8 year life and gives a 5-yr warranty. This is less than 20% of the “expected” life of the bulb. Using this bulb for only three hrs a day for five years is a total of 5475 hrs, for a cost of [5475hrs * 6W == 32.85 KWhr * 0.10 $/KWhr = $3.29] for the electricity for the 5 years.
The electricity used by the CFL is 10W/6W ~ 1.67 times more, or 1.67 * 3.29 = $5.48 for the five years.
The LED bulb costs $10, the CFL costs $1.67 (assuming $10 for a pack of 6 bulbs; I bought a pack recently for under $9 including 6% sales tax), so if both fail just after five years of operation, we’ve spent $13.29 for operating the LED bulb and we’ve spent only $7.17 for the CFL, for a savings of $6.12 for the CFL bulb.
So, where’s the break-even point? Let’s try to calculate this:
Cost of operating for one year,
assume 3 hrs/day * 365 = 1095 hrs/yr
assume 1 KW = $0.10
assume 1 bulb lasts the entire time (for now)
Initial Cost(LED) + (CostToUse(LED)/yr) * Yrs = Initial Cost(CFL) + (CostToUse(CFL)/yr) * Yrs
The Cost To Use the bulbs (using 1 KWhr = $0.10) is:
LED: 1095*6W*0.10/1000 = $.66/yr
CFL: 1095*10W*0.10/1000 = $1.10/yr
$10 + Yrs*(.66/yr) = $1.67 + Yrs*($1.10/yr)
10 – 1.67 = Yrs * (1.10 – .66)/yr
8.33 = Yrs * (0.44)
Yrs = 8.33/.44 ~ 18.9 years.
This is about nine years longer than CFL bulbs state as their expected life, so adjusting the cost for using two CFL bulbs, this reduces the break-even point to about 15.2 years.
At the present cost of the less expensive LED bulbs and expecting the bulbs to last almost the complete exaggerated life expectancy of the LEDs means that the LED bulbs will probably never pay for themselves when compared to the CFL bulbs if the bulbs all die in under 15.2 years. This is 3 – 7 times the warranty periods I’ve seen for LED bulbs. It simply isn’t likely to happen.