Hallway Calculations
Room Size: 18 x 4 ft or 72ft2
Above Sink: 3 x 4 ft or 12ft2
General Area = 72ft2 x 5fc = 360 lumens
Above Sink: 12ft2 x 70 fc = 840 lumens
Incandescent Light Bulbs:
60 watt gives off 855 lumens so:
Hallway: 360 lumens/ 855 lumens = 0.42 bulbs or approximately 1-60 watt incandescent bulb is needed to light the hallway.
Above Sink: 840 lumens/ 855 lumens = 0.98 bulbs or approximately 1- 60 watt incandescent bulb is needed to light above the sink.
100 watt gives off 1690 lumens so:
Hallway: 360 lumens/ 1690 lumens = 0.21 bulbs or approximately 1 - 100 watt incandescent bulb is needed to light the hallway.
Above Sink: 840 lumens/ 1690 lumens = 0.49 bulbs or approximately 1-100 watt incandescent bulb is needed to light above the sink.
CFL's
15 watt gives off 900 lumens so:
Hallway: 360 lumens/ 900 lumens = 0.4 bulbs or approximately 1-15 watt CFL is needed to light the hallway.
Above Sink: 840 lumens/ 900 lumens = 0.93 bulbs or approximately 1- 15 watt CFL is needed to light above the sink.
26 watt gives off 1750 lumens so:
Hallway: 360 lumens/ 1750 lumens = 0.20 bulbs or approximately 1- 26 watt CFL is needed to light the hallway.
Above Sink: 840 lumens/ 1750 lumens = 0.48 bulbs or approximately 1- 26 watt CFL is needed to light above the sink.
Prices-
Incandescent:
Each 60 watt incandescent bulb costs approximately $0.50 and has a lifetime of 750 hours while each 100 watt incandescent bulb cost approximately $0.80 and has a lifetime of 750 hours.
60 watt bulbs would cost: 2 bulbs x $0.50 = $1.00
100 watt bulbs would cost: 2 bulbs x $0.80 = $1.60
CFL's:
Each 15 watt CFL costs approximately $2.50 and has a lifetime of 8000 hours while each 26 watt CFL costs approximately $3.75 and has a lifetime of 8000 hours.
15 watt bulbs would cost: 2 bulbs x $ 2.50 = $5.00
26 watt bulbs would cost: 2 bulbs x $3.75 = $7.50
Which is more efficient and be less costly?
8000 hours/750 hours = 10.66 or approximately 11 changes which means:
Incandescent: $1.00 + $1.60 = $2.60 x 11 = $28.60
CFL's: $5.00 + $7.50 = $12.50- LESS COSTLY
Efficiency:
Incandescent: 2 bulbs at 60 watts= 120 watts x 8000 hrs = 960,000 kh or 960 kwh
Incandescent: 2 bulbs at 100 watts = 200 watts x 8000 hrs = 1,600,000 kh or 1600 kwh
Incandescent: 960 kwh + 1600 kwh = 2560 kwh x $0.10 = $256.00
Total Cost: $256.00 + $28.60 = $284.60
CFL's: 2 bulbs at 15 watts = 30 watts x 8000 hrs = 240,000 kh or 240 kwh
CFL's: 2 bulbs at 26 watts = 52 watts x 8000 hrs = 416,000 kh or 416 kwh
CFL's: 240 kwh + 416 kwh = 656 kwh x $0.10 = $65.60
Total Cost: $65.60 + $12.50 = $78.10
These calculations again show that CFL's are generally more efficient and less costly in the long run.