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Calculating savings from replaced products

You can manually calculate energy cost of any product using the following formula

$$$ = W * H * T * 365 / 1000, where

W = appliance or product wattage.

H = average hours of usage per day

T = current electrical tariff (from your electricity bill)

365 = to calculate cost per year (use any period required)

1000 = divide by 1000 to convert result to kWh.

**Globes, downlights **

To calculate savings from replacing 100W incandescent globe with 20W equivalent CFL, used approximately 2 hours/day on a 25c per kWh tariff,

Saving = (100W-20W) * 2 * $0.25 * 365 / 1000 = $14.60 per year

Repeat the formula for all other incandescent lights to calculate total savings of light replacement. For downlights, use 50W for existing halogen lights and 6W for LED replacement.

**SPC's**

To calculate savings from installing standby power controllers you must know your appliances' standby energy usage in Watts. If you don;t have this information, you can use the average values to approximate the saving:

TV (large) = 20W

TV(other) = 10W

VCR = 9W

DVD = 5W

gaming = 15W

Set top box = 7W

For example, to calculate savings from standby power controller installed with TV, set top box and a dvd player, used approximately 3 hours/day (21hr standby), and 25c per kWh tariff, using the same formula,

Saving = (20W+7W+5W) * 21 * $0.25 * 365 / 1000 = $61.32 / year

**Shower heads**

The savings from low-flow showerheads are measured by the amount of saved hot water, for which the energy used to heat up the extra water can be calculated. A shower head with flow rating of 9L per minute or less is considered low-flow. By comparison, old shower heads can use as much as 30L per minute.

Assuming 4 min shower is taken every day, with hot and cold water mixed 1:1, the amount of hot water saved by using low-flow shower head is

Saving = (30L-9L) * 4min / 2 = 42L per shower.

With an average 135L hot water tank this means saving of approx 1/3rd of the tank. To calculate $ saving, we use pre-calculated costs of heating 1L of water at 1$/kWh tariff. These values are

c = $0.05305 for average electric HWS, and

c = $0.02685 for average gas HWS

Thus, the saving in our example

$$$ = 0.05305 * 42L * $0.25 = $0.28 per shower, or $102.20 per year