Replacing lightbulbs with CFLs

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Replacing lightbulbs with CFLs

Postby Mogul on Fri Mar 06, 2009 12:47 pm

This past fall, I replaced almost all of the incandescent light bulbs in my two rentals with CFLs (Compact Fluorescent Lights - the swirly ones). My thinking is that since most renters seem to leave the lights on throughout their entire stay, then saving a few dollars each month would be nice. I was wondering what my ROI (return on investment) would be on this change, but I found some really good deals at Home Depot and Lowes when they had specials on CFLs and probably spent a total of about $100 to make the change. I was hoping to save $10 to $20 per month per house, not much but every little bit helps.

WELL, I got the electric bill last for January (I have a ski house) and both were about $100 less than last year's bill. I thought to myself that this must be a fluke thing. When I opened up this month's electric bill (for the month of February, another packed month of renters), both bills were again about $100 less then the previous year! I am still having a hard time believing that I am actually saving this much. :shock:

If you really think about it, if you replace a 60, 65, or 90 Watt bulb with a 13 or 14 watt bulb and leave it on for a few days, you'll save a little - do that with 50 bulbs, it begins to add up.

Here is how to do the math: :ugeek:
1) Find and write down the wattage of the bulb (or multiply the wattage by the number of bulbs in a light fixture)
ex. Four 60 Watt bulbs in a bedroom light fixture = 4*60=240 Watts
2) Divide this number by 1,000 to convert watts to kilowatts (1,000 Watts = 1 kW)
ex. 240 Watts divided by 1,000 = 0.24 kW
3) Multiply the kilowatts by the number of hours this light fixture will be used each month
ex. 8hr/day for a 3-day weekend rental, 4 weekend rental per month = 0.24kW x [4*(3*8)] = 0.24 kW x [4*(24)] = 0.24*96 = 23.04 kW-hours per month
4) Multiply the total number of kWh (kilowatt hours) used each month by the current cost of electricity per kWh
ex. 23.04 kWh * 14.9¢ = $3.43 PER MONTH for that one single light fixture

So I will do an example with one of my rentals for you, I am going to use rough estimates to get the point across.
Original bulbs:
- 50 bulbs are replaced, the average wattage of all 50 bulbs is 65W --> (50*65)/1,000 = 3.25 kW
- The average time these lights are on are 8hr/day for a 3-day weekend rental, 4 weekend rental per month --> 96 hours/month of usage --> 3.25kW * 96h = 312 kWh
- The cost of electricity is 14.9¢ per kWh --> 312 * .149 = $46.49/month

CFL replacements:
- 50 bulbs are replaced, the average wattage of all 50 CFLs are 13 --> (50*13)/1,000 = 0.65kW
- The average time these lights are on are 8hr/day for a 3-day weekend rental, 4 weekend rental per month --> 96 hours/month of usage --> 0.65kW * 96h = 62.4kWh
- The cost of electricity is 14.9¢ per kWh --> 62.4* .149 = $9.30/month

So the savings in this example is $37.19 each month! 8-)


*** How I am getting about $100 savings is still a little baffling, but the bills don't lie!
www.SundayRiverHouse.com
Beautiful 4 Season Vacation Home Near th Sunday River Ski Mountain in Maine
Mogul
 
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Joined: Fri Nov 28, 2008 1:20 am
Location: Maine

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