Lighting Energy Savings worksheet

1. Money saved per year: $35.64

1. Find how many hours a year the lights are on: hours per day × days per year

   $2\text{\hspace{0.17em}h}\times 300$$=600\text{\hspace{0.17em}h}$

2. Find the old bulbs' yearly energy: bulbs × watts × hours, then ÷ 1,000 to turn watt-hours into the kilowatt-hours on your bill

   $\frac{9\times 70\text{\hspace{0.17em}W}\times 600\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=378\text{\hspace{0.17em}kWh}$

3. Find the new bulbs' yearly energy the same way

   $\frac{9\times 10\text{\hspace{0.17em}W}\times 600\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=54\text{\hspace{0.17em}kWh}$

4. Subtract to find the energy you save each year

   $378-54$$=324\text{\hspace{0.17em}kWh}$

5. Find the money saved each year: the energy saved × your electricity rate

   $324\text{\hspace{0.17em}kWh}\times \mathrm{\$0.11}\text{\hspace{0.17em}/kWh}$$=\mathrm{\$35.64}$

6. Find the payback time: what the new bulbs cost ÷ what they save each year, then × 12 to get months

   $\frac{\mathrm{\$27.00}}{\mathrm{\$35.64}}\times 12$$=9.0909090909\text{\hspace{0.17em}months}$

2. Money saved per year: $90.72

1. Find how many hours a year the lights are on: hours per day × days per year

   $2\text{\hspace{0.17em}h}\times 350$$=700\text{\hspace{0.17em}h}$

2. Find the old bulbs' yearly energy: bulbs × watts × hours, then ÷ 1,000 to turn watt-hours into the kilowatt-hours on your bill

   $\frac{12\times 52\text{\hspace{0.17em}W}\times 700\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=436.8\text{\hspace{0.17em}kWh}$

3. Find the new bulbs' yearly energy the same way

   $\frac{12\times 7\text{\hspace{0.17em}W}\times 700\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=58.8\text{\hspace{0.17em}kWh}$

4. Subtract to find the energy you save each year

   $436.8-58.8$$=378\text{\hspace{0.17em}kWh}$

5. Find the money saved each year: the energy saved × your electricity rate

   $378\text{\hspace{0.17em}kWh}\times \mathrm{\$0.24}\text{\hspace{0.17em}/kWh}$$=\mathrm{\$90.72}$

6. Find the payback time: what the new bulbs cost ÷ what they save each year, then × 12 to get months

   $\frac{\mathrm{\$48.00}}{\mathrm{\$90.72}}\times 12$$=6.3492063492\text{\hspace{0.17em}months}$

3. Money saved per year: $135.31

1. Find how many hours a year the lights are on: hours per day × days per year

   $3\text{\hspace{0.17em}h}\times 360$$=\mathrm{1,080}\text{\hspace{0.17em}h}$

2. Find the old bulbs' yearly energy: bulbs × watts × hours, then ÷ 1,000 to turn watt-hours into the kilowatt-hours on your bill

   $\frac{11\times 74\text{\hspace{0.17em}W}\times \mathrm{1,080}\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=879.12\text{\hspace{0.17em}kWh}$

3. Find the new bulbs' yearly energy the same way

   $\frac{11\times 7\text{\hspace{0.17em}W}\times \mathrm{1,080}\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=83.16\text{\hspace{0.17em}kWh}$

4. Subtract to find the energy you save each year

   $879.12-83.16$$=795.96\text{\hspace{0.17em}kWh}$

5. Find the money saved each year: the energy saved × your electricity rate

   $795.96\text{\hspace{0.17em}kWh}\times \mathrm{\$0.17}\text{\hspace{0.17em}/kWh}$$=\mathrm{\$135.31}$

6. Find the payback time: what the new bulbs cost ÷ what they save each year, then × 12 to get months

   $\frac{\mathrm{\$22.00}}{\mathrm{\$135.31}}\times 12$$=1.9510291679\text{\hspace{0.17em}months}$

4. Money saved per year: $112.15

1. Find how many hours a year the lights are on: hours per day × days per year

   $3\text{\hspace{0.17em}h}\times 320$$=960\text{\hspace{0.17em}h}$

2. Find the old bulbs' yearly energy: bulbs × watts × hours, then ÷ 1,000 to turn watt-hours into the kilowatt-hours on your bill

   $\frac{9\times 68\text{\hspace{0.17em}W}\times 960\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=587.52\text{\hspace{0.17em}kWh}$

3. Find the new bulbs' yearly energy the same way

   $\frac{9\times 9\text{\hspace{0.17em}W}\times 960\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=77.76\text{\hspace{0.17em}kWh}$

4. Subtract to find the energy you save each year

   $587.52-77.76$$=509.76\text{\hspace{0.17em}kWh}$

5. Find the money saved each year: the energy saved × your electricity rate

   $509.76\text{\hspace{0.17em}kWh}\times \mathrm{\$0.22}\text{\hspace{0.17em}/kWh}$$=\mathrm{\$112.15}$

6. Find the payback time: what the new bulbs cost ÷ what they save each year, then × 12 to get months

   $\frac{\mathrm{\$27.00}}{\mathrm{\$112.15}}\times 12$$=2.8890600924\text{\hspace{0.17em}months}$

5. Money saved per year: $53.82

1. Find how many hours a year the lights are on: hours per day × days per year

   $3\text{\hspace{0.17em}h}\times 300$$=900\text{\hspace{0.17em}h}$

2. Find the old bulbs' yearly energy: bulbs × watts × hours, then ÷ 1,000 to turn watt-hours into the kilowatt-hours on your bill

   $\frac{10\times 54\text{\hspace{0.17em}W}\times 900\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=486\text{\hspace{0.17em}kWh}$

3. Find the new bulbs' yearly energy the same way

   $\frac{10\times 8\text{\hspace{0.17em}W}\times 900\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=72\text{\hspace{0.17em}kWh}$

4. Subtract to find the energy you save each year

   $486-72$$=414\text{\hspace{0.17em}kWh}$

5. Find the money saved each year: the energy saved × your electricity rate

   $414\text{\hspace{0.17em}kWh}\times \mathrm{\$0.13}\text{\hspace{0.17em}/kWh}$$=\mathrm{\$53.82}$

6. Find the payback time: what the new bulbs cost ÷ what they save each year, then × 12 to get months

   $\frac{\mathrm{\$30.00}}{\mathrm{\$53.82}}\times 12$$=6.6889632107\text{\hspace{0.17em}months}$

6. Money saved per year: $45.36

1. Find how many hours a year the lights are on: hours per day × days per year

   $2\text{\hspace{0.17em}h}\times 350$$=700\text{\hspace{0.17em}h}$

2. Find the old bulbs' yearly energy: bulbs × watts × hours, then ÷ 1,000 to turn watt-hours into the kilowatt-hours on your bill

   $\frac{8\times 55\text{\hspace{0.17em}W}\times 700\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=308\text{\hspace{0.17em}kWh}$

3. Find the new bulbs' yearly energy the same way

   $\frac{8\times 10\text{\hspace{0.17em}W}\times 700\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=56\text{\hspace{0.17em}kWh}$

4. Subtract to find the energy you save each year

   $308-56$$=252\text{\hspace{0.17em}kWh}$

5. Find the money saved each year: the energy saved × your electricity rate

   $252\text{\hspace{0.17em}kWh}\times \mathrm{\$0.18}\text{\hspace{0.17em}/kWh}$$=\mathrm{\$45.36}$

6. Find the payback time: what the new bulbs cost ÷ what they save each year, then × 12 to get months

   $\frac{\mathrm{\$24.00}}{\mathrm{\$45.36}}\times 12$$=6.3492063492\text{\hspace{0.17em}months}$

7. Money saved per year: $36.54

1. Find how many hours a year the lights are on: hours per day × days per year

   $3\text{\hspace{0.17em}h}\times 350$$=\mathrm{1,050}\text{\hspace{0.17em}h}$

2. Find the old bulbs' yearly energy: bulbs × watts × hours, then ÷ 1,000 to turn watt-hours into the kilowatt-hours on your bill

   $\frac{10\times 40\text{\hspace{0.17em}W}\times \mathrm{1,050}\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=420\text{\hspace{0.17em}kWh}$

3. Find the new bulbs' yearly energy the same way

   $\frac{10\times 11\text{\hspace{0.17em}W}\times \mathrm{1,050}\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=115.5\text{\hspace{0.17em}kWh}$

4. Subtract to find the energy you save each year

   $420-115.5$$=304.5\text{\hspace{0.17em}kWh}$

5. Find the money saved each year: the energy saved × your electricity rate

   $304.5\text{\hspace{0.17em}kWh}\times \mathrm{\$0.12}\text{\hspace{0.17em}/kWh}$$=\mathrm{\$36.54}$

6. Find the payback time: what the new bulbs cost ÷ what they save each year, then × 12 to get months

   $\frac{\mathrm{\$20.00}}{\mathrm{\$36.54}}\times 12$$=6.5681444992\text{\hspace{0.17em}months}$

8. Money saved per year: $114.91

1. Find how many hours a year the lights are on: hours per day × days per year

   $4\text{\hspace{0.17em}h}\times 350$$=\mathrm{1,400}\text{\hspace{0.17em}h}$

2. Find the old bulbs' yearly energy: bulbs × watts × hours, then ÷ 1,000 to turn watt-hours into the kilowatt-hours on your bill

   $\frac{9\times 66\text{\hspace{0.17em}W}\times \mathrm{1,400}\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=831.6\text{\hspace{0.17em}kWh}$

3. Find the new bulbs' yearly energy the same way

   $\frac{9\times 9\text{\hspace{0.17em}W}\times \mathrm{1,400}\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=113.4\text{\hspace{0.17em}kWh}$

4. Subtract to find the energy you save each year

   $831.6-113.4$$=718.2\text{\hspace{0.17em}kWh}$

5. Find the money saved each year: the energy saved × your electricity rate

   $718.2\text{\hspace{0.17em}kWh}\times \mathrm{\$0.16}\text{\hspace{0.17em}/kWh}$$=\mathrm{\$114.91}$

6. Find the payback time: what the new bulbs cost ÷ what they save each year, then × 12 to get months

   $\frac{\mathrm{\$36.00}}{\mathrm{\$114.91}}\times 12$$=3.7593984962\text{\hspace{0.17em}months}$

9. Money saved per year: $87.52

1. Find how many hours a year the lights are on: hours per day × days per year

   $3\text{\hspace{0.17em}h}\times 325$$=975\text{\hspace{0.17em}h}$

2. Find the old bulbs' yearly energy: bulbs × watts × hours, then ÷ 1,000 to turn watt-hours into the kilowatt-hours on your bill

   $\frac{11\times 60\text{\hspace{0.17em}W}\times 975\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=643.5\text{\hspace{0.17em}kWh}$

3. Find the new bulbs' yearly energy the same way

   $\frac{11\times 12\text{\hspace{0.17em}W}\times 975\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=128.7\text{\hspace{0.17em}kWh}$

4. Subtract to find the energy you save each year

   $643.5-128.7$$=514.8\text{\hspace{0.17em}kWh}$

5. Find the money saved each year: the energy saved × your electricity rate

   $514.8\text{\hspace{0.17em}kWh}\times \mathrm{\$0.17}\text{\hspace{0.17em}/kWh}$$=\mathrm{\$87.52}$

6. Find the payback time: what the new bulbs cost ÷ what they save each year, then × 12 to get months

   $\frac{\mathrm{\$33.00}}{\mathrm{\$87.52}}\times 12$$=4.5248868778\text{\hspace{0.17em}months}$

10. Money saved per year: $145.60

1. Find how many hours a year the lights are on: hours per day × days per year

   $4\text{\hspace{0.17em}h}\times 350$$=\mathrm{1,400}\text{\hspace{0.17em}h}$

2. Find the old bulbs' yearly energy: bulbs × watts × hours, then ÷ 1,000 to turn watt-hours into the kilowatt-hours on your bill

   $\frac{10\times 60\text{\hspace{0.17em}W}\times \mathrm{1,400}\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=840\text{\hspace{0.17em}kWh}$

3. Find the new bulbs' yearly energy the same way

   $\frac{10\times 8\text{\hspace{0.17em}W}\times \mathrm{1,400}\text{\hspace{0.17em}h}}{\mathrm{1,000}}$$=112\text{\hspace{0.17em}kWh}$

4. Subtract to find the energy you save each year

   $840-112$$=728\text{\hspace{0.17em}kWh}$

5. Find the money saved each year: the energy saved × your electricity rate

   $728\text{\hspace{0.17em}kWh}\times \mathrm{\$0.20}\text{\hspace{0.17em}/kWh}$$=\mathrm{\$145.60}$

6. Find the payback time: what the new bulbs cost ÷ what they save each year, then × 12 to get months

   $\frac{\mathrm{\$20.00}}{\mathrm{\$145.60}}\times 12$$=1.6483516484\text{\hspace{0.17em}months}$