Sample Savings Calculation
A small commercial store was remodeled in the early 1980s. The lighting in the store has not changed much since the store was remodeled. A Business Energy Services Team representative visited the store and performed a facility assessment to identify cost-effective energy savings opportunities. The proposed retrofits are summarized in the table below:
|
Qty |
Existing
Fixture Description |
Wattage
per fixture |
Replacement
Fixture Description |
Wattage
per fixture |
Cost |
Savings
(kW) |
Savings
per year (kWh)* |
|
15 |
65 W Incandescent |
65 |
13 W Screw-in CFL |
13 |
$105.00 |
0.78 |
2,340 |
|
10 |
2 lamp -4 34W T12 with std
ballast |
84 |
2 lamp -4 32W T8 with low power
ballast |
58 |
$375.60 |
0.26 |
780 |
|
2 |
4 lamp -4 34W T12 with 2 std
ballasts |
168 |
4 lamp -4 32W T8 with low power
ballast |
98 |
$97.14 |
0.14 |
420 |
|
TOTAL: |
$577.74 |
1.18 |
3,540 |
||||
*Assumes
the store hours (and the lighting operating hours) are 3,000 hours per
year.
The following table summarizes the outcome of the project above. The total rebates are $436, which is 75% of the project cost. The payback period is 0.27 years. In other words, it would take a little over 3 months to payback the cost of the project after taking into account the dollar savings (on energy bills) and rebate amount.
|
Total Peak kW Reduced |
1.18 |
Total Project Cost |
$577.74 |
|
Total Annual kWh Savings |
3,540 |
Total Rebates |
$436 |
|
Total Annual Therm Savings |
0 |
Total Customer Payment |
$141.74 |
|
Total Annual Dollar Savings* |
$531 |
Payback Period (in years) |
0.27 |
*Assumes that the electricity rate is
$0.15/kWh.
Where,
Total
Peak kW Reduced = Percent on peak X kW Savings per line item (Percent on peak is 100% in
this example lights are on during business hours)
kW
Savings = # of fixtures X (Existing wattage Retrofitted wattage)
Total
Annual kWh Savings (for lighting only) = kW Savings * operating hours
Total
Annual Dollar Savings = kWh savings per year X electricity rate
Total
Customer Payment = Total Project Cost Total Rebates
Payback Period = (Project Cost Rebate Amount) / Total kWh cost savings, # of years it will take to payback the cost of the project
The Total Annual Dollar Savings are based
on electricity/gas rates. These rates can vary based on the business
electricity/gas rate plan. In the following table, we indicate the rates for
the various rate plans available to eligible customers.