12/05/06

Definition:  A footcandle is the value of measurement given by the illumination of a light.  
Light output is measured in lumens and the distribution of light over a horizontal surface
is measured in footcandles.

Selecting the light bulbs:

Fluorescent:

15 Watt Fluorescent
15 watts
$1.89 each
Lifetime:  10,000 hours
900 lumens

40 Watt Fluorescent
40 watts
$9.98 each
Lifetime:  10,000 hours
2,600 lumens

85 Watt Fluorescent
85 watts
$22.22 each
Lifetime:  8,000 hours
4,200 lumens

Incandescent:

15 Watt Incandescent
15 watts
$1.12 each
Lifetime:  5,000 hours
90 lumens

40 Watt Incandescent
40 watts
$0.69 each
Lifetime:  5,000 hours
175 lumens

75 Watt Incandescent
75 watts
$1.20 each
Lifetime:  6,000 hours
855 lumens

First step:  Determining the lumens required in each room
By definition of measurement, 1 footcandle=1 lumen per square foot.  So, by taking the
number of footcandles required by each room and multiplying it by the square footage of
each room, you can determine the number of lumens required to light the entire room.

Results are as follows:  Living room (18*17 lumens/sq. ft)*20 footcandles=6,120 lumens
                                        Kitchen (9*10 lumens/sq. ft)*30 footcandles=2,700 lumens
                                        Stove (2.5*3 lumens/sq. ft)*70 foocandles=525 lumens
                                        Dining Room (9*10 lumens/sq. ft)*30 footcandles=2,700 lumens
                                        Bedroom one (13*19 lumens/sq. ft)*10 footcandles=2,470 lumens
                                        Bedroom two (14*19 lumens/sq. ft)*10 footcandles=2,660 lumens
                                        Hallway (18*4 lumens/sq.ft)*5 footcandles=360 lumens
                                        Sink (4*3 lumens/sq. ft)*70 footcandles=840 lumens
                                        Bathroom (9*7 lumens/sq. ft)*70 footcandles=4,410 lumens

Step 2:  Number of bulbs needed.

These figures were found by taking the required number of footcandles found in the first
step and dividing that number by the lumens of each particular light bulb.  This shows us
the light bulbs of each typed that each room requires in order to be sufficiently lit.

Results are as follows:

Incandescent:  Living room:  (6,120 lumens/855 lumens)=3 (75 watt bulbs)
                                                (6,120 lumens/additional 175 lumens)=3 (40 watt bulbs)
            
                       Kitchen:  (2,700 lumens/855 lumens)=4 (75 watt bulbs)
                                        (2,700 lumens/additional 175 lumens)=2 (40 watt bulbs)

                       Stove:  3 (40 watt bulbs)
                       
                       Dining Room:  3 (75 watt bulbs)
                                                   1 (40 watt bulb)

                       Bedroom 1:  3 (75 watt bulbs)

                       Bedroom 2:  3 (75 watt bulbs)
                                              1 (15 watt bulb)

                       Hallway:  2 (40 watt bulbs)
                                         
                       Sink:  5 (40 watt bulbs)

                       Bathroom:  5 (75 watt bulbs)

Fluorescent:  Living room:  2 (40 watt bulbs)
                                             1 (15 watt bulb)

                    Kitchen:  1 (40 watt bulb)

                    Stove:  1 (15 watt bulb)

                    Dining Room:  1 (40 watt bulb)

                    Bedroom 1:  1 (40 watt bulb)

                    Bedroom 2:  1 (40 watt bulb)

                    Hallway:  1 (15 watt bulb)

                    Sink:  1 (15 watt bulb)

                    Bathroom:  1 (40 watt bulb)

Step 3:  Determining the number of bulb changes required.  This is done by dividing the
lifetime of fluorescent bulbs (generally a longer lifetime) by the lifetime of an incandescent
bulb (generally a shorter lifetime).  For 15 watt and 40 watt bulbs, you get 10,000
hours/5,000 hours or the answer of 2.  This means that for every change of a fluorescent
15 or 40 watt bulb, you will have to change a similar incandescent bulb twice.  With an 85
watt fluorescent bulb of 8,000 hours/6,000 hours for a 75 watt incandescent we get a
1.333333 change, or for every 85 watt fluorescent bulb we need 1.333333 incandescent
bulbs.  These numbers can then be put into each room, multiplying the number of
changes by the incandescent bulbs needed.  The resulting number will give us the total
number of incandescent bulbs needed over the lifetime of the fluorescent bulbs.

The Results are as follows:  Living Room: 4 (75 watt bulbs), 6 (40 watt bulbs)
                                                Kitchen: 4, (75 watt bulbs), 2 (40 watt bulbs)
                                                Stove: 6 (40 watt bulbs)
                                                Dining Room: 4 (75 watt bulbs), 2 (40 watt bulbs)
                                                Bedroom 1: 4 (75 watt bulbs)
                                                Hallway:  4 (40 watt bulbs)
                                                Sink:  10 (40 watt bulbs)
                                                Bedroom 2:  4 (75 watt bulbs), 2 (15 watt bulbs)
                                                Bath:  7 (75 watt bulbs)

Step 4:  Determining the cost of the bulbs.  This is done by multiplying the number of
bulbs required over the lifetime by the cost per each individual bulb.

Results are as follows:

Incandescent:  Living Room:  4 (75 watt bulbs)*$1.20=4.8+ 6 (40 watt bulbs)*$0.69=$4.14
                                           $4.80+$4.14=$8.94
                        Kitchen:  4*$1.20 + 2*$0.69= $6.18
                        Stove:  6*$0.69= $4.14
                        Dining Room:  4*$1.20 + 2*$0.69 = $6.18
                        Bedroom 1:  4*$1.20= $4.80
                        Hallway:  4*$0.69= $2.76
                        Sink:  10*$0.69=  $6.90
                        Bedroom 2:  4*$1.20 + 2*$1.12=  $7.04
                        Bathroom:  7*$1.20=  $8.40
Total:  (All rooms combined)  $55.34

Fluorescent:  Living Room:  2*$9.98 + 1*$1.89 = $21.85
                      Kitchen:  1*$9.98 = $9.98
                      Stove:  1*$1.89= $1.89
                      Dinning Room:  1*$9.98= $9.98
                      Bedroom 1:  1*$9.98= $9.98
                      Hallway:  1*$1.89= $1.89
                      Sink:  1*$1.89= $1.89
                      Bedroom 2:  1*$9.98= $9.98
                     Bathroom:  1*$22.22= $22.22
Total:  (All rooms combined)  $89.66

Step 5:  Power Requirements.  This step shows how much each bulb in the apartment
uses.  When totaled, it shows the total energy that all of the bulbs combined use.  It is
figured out by multiplying the number of bulbs by the watts per each bulb.

Results are as follows:

Incandescent:  Living Room=  4*75watts=300watts
                                                   6*40 watts=240watts
                                                   Total=540 watts
                        Kitchen=  4*75 watts=300watts
                                         2*40 watts=80watts
                        Stove=240 watts
                        Dinning Room=380 watts
                        Bedroom 1=300 watts
                        Hallway=160 watts
                        Sink=400 watts
                        Bedroom 2=330 watts
                        Bathroom=525 watts

Fluorescent:  Living Room=  2*40 watts=80 watts
                                                 1*15 watts=15 watts
                                                 Total=95 watts
                        Kitchen=  1*40 watts=40 watts
                        Stove=15 watts
                        Dining Room=40 watts
                        Bedroom 1=40 watts
                        Hallway=15 watts
                        Sink=15 watts
                        Bedroom 2=40 watts
                        Bathroom=85 watts

Step 6:  Determining Total Energy used.  This is done by multiplying the power
requirements from step 5 by the lifetime of the typical fluorescent bulb (assumed to be
10,000 hours) and then divided by 1,000 to get kWh.  This shows how much each light
bulb uses over its entire lifetime.

Results are as follows:

Incandescent:  Living Room:  (540watts*10,000hours)/1,000=5,400 kWh
                        Kitchen:  (380 watts*10,000 hours)/1,000=3,800 kWh
                        Stove:  2,400 kWh
                        Dining Room:  3,800 kWh
                        Bedroom 1:  3,000 kWh
                        Hallway:  1,600 kWh
                        Sink:  4,000 kWh
                        Bedroom 2:  3,300 kWh
                        Bathroom:  5,250 kWh

Fluorescent:  Living Room:  (95 watts*10,000 hours)/1,000=950 kWh
                      Kitchen:  (40 watts*10,000 hours)/1,000=400 kWh
                        Stove:  150 kWh
                        Dining Room:  400 kWh
                        Bedroom 1:  400 kWh
                        Hallway:  150 kWh
                        Sink:  150 kWh
                        Bedroom 2:  400 kWh
                        Bathroom:  850 kWh

Step 7:  Cost of Energy.  The results of this step show exactly how much energy costs for
each individual light.  The total of this shows the amount of money you would pay on the
amount of bulbs in the apartment at the end of the 10,000 hour lifetime.  Answer are
arrived at by multiplying the cost of energy (assumed to be $0.08/kWh) by the amount of
kWh arrived at in step 6.

Results are as follows:

Incandescent:  Living Room:  (5,400 kWh)*$0.08/kWh=$432
                        Kitchen:  (3,800 kWh)*$0.08/kWh=$304
                        Stove:  $192
                        Dining Room:  $304
                        Bedroom 1:  $240
                        Hallway:  $128
                        Sink:  $320
                        Bedroom 2:  $264
                        Bathroom:  $420
Total:  $2,604

Fluorescent:  Living Room:  (950 kWh)*$0.08/kWh=$76
                      Kitchen:  (400 kWh)*$0.08/kWh=$32
                      Stove:  $12
                      Dining Room:  $32
                      Bedroom 1:  $32
                      Hallway:  $12
                      Sink:  $12
                      Bedroom 2:  $32
                      Bathroom:  $68
Total:  $308

Step 8:  Cost Comparison.  Through the first seven steps, we found the lighting options
we could put into this hypothetical apartment.  From these results, we are now ready to
compare the incandescent bulbs to the fluorescent bulbs to determine which of the two
types is more economical.  To do this, we will add the purchase cost of each type to the
cost of energy (step 7) of each type.

Results are as follows:

Incandescent:  Purchase cost:  $55.34
                         Cost of Energy:  $2,609.00
     Total:  $2,664.34

Fluorescent:  Purchase cost:  $89.60
                      Cost of Energy:  $308.00
     Total:  $397.60

Step 9:  Drawing conclusions.  Now that we know the total cost of both incandescent and
fluorescent light, it is time to see exactly how much money we would have saved if we
invested in fluorescent lights for this hypothetical apartment.  We find this by subtracting
the total cost of incandescent lights by the total cost of fluorescent lights.

Results are as follows:

$2,609.00
- $   397.60
___________
$2,266.74

Questions:

1.  Which lighting scheme is more economical?

Answer:  Fluorescent.  If we used fluorescent lighting in this example over incandescent
lighting, we would save $2,266.74 over a period of 10,000 hours.

2.  What is the total energy saved by fluorescent lighting?

Answer:  Incandescent lights would use 32,550 kWh of energy.  Fluorescent would use
3,850 kWh of power.  When subtracted, we see that we would save 28,700 kWh worth of
power given fluorescent lighting.

3.  How much money will be saved over the lifetime, while using fluorescent lighting?

Answer:  As shown in the answer to question 1, $2,266.74.

4.  What are the environmental consequences of choosing energy efficient fluorescent
lighting?

Answer:  When plugging the figures into the environmental calculator at
http://www.cleanerandgreener.org/resources/emission_reductions.htm, it is shown that
given this situation, we would send 57 pounds of CO2 (a greenhouse gas) into the
atmosphere along with a milligram of Mercury (Hg).



Conclusion:  From this analysis of lighting, we can see that the benefits of fluorescent
lighting are very great when considering the alternative option of incandescent lighting.  It
is clearly the more economically sound conclusion.



This concludes the research portion of the project.  If you have any questions, please go
to the "Contact" bar on the top left of this page where you will find my e-mail address.  
Thank you for your time.

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This site was last updated 12/05/06