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Lighting Costs Comparision Calculator

Energy efficient LED lamps for lighting are very popular. They certainly cost less to run than conventional lamps. But how much do you really save, and how long does it take to pay off the purchase price of the lamps?

This calculator shows how much your existing lamps cost to run, how much you can save each year with energy saving lamps, how long it will take to pay off the purchase price from the saving you make as well as showing the approximate reduction of CO2 emissions .

You need to input 7 figures:small calculator

1. Cost of one kilowatt hour (kWh) of electricity. This should be on your power bill.

Eg: your electricity costs 25 cents/kWh – enter 0.25 in the calculator

While the results are shown in $’s, they will be correct for whatever currency you use here.

2. How many hours the lamps are on each day. This is an estimate of the average hours used.

3. Number of lamps you are thinking of upgrading, or the number of lamps in one room.

4. Wattage of the existing lamps. Halogen down lights are typically 50 watts each. Most lamps have their wattage written on them.

5. Wattage of the proposed new lamps. Energy efficient lamps may only draw 4 watts, 7 watts or some other low value. Enter the wattage value of the lamps you propose to use.

6. Cost of new lamps. Enter the cost for one of the new lamps. The calculator will multiply this cost by the number of lamps entered earlier.

7. Total cost of installation labor. Enter the estimated cost for an electrician to change over all the lights. If you are doing this yourself, or a friend is doing it for free, enter 0.

Optional: Generator Type. This is used to determine the CO emissions. Select the type of electricity generator your supplier mostly uses. If you don’t know, don’t worry, the energy savings will still be calculated, but the emissions savings may not be correct.

For those who need to know, the calculations are based on the following formulas:

\large Yearly\ cost = {\left(\frac{cost \, per \, kWh \times hours \, of \, use \times lamp \,wattage \times No.\, of \, Lamps}{1000}\right) \times 365}

Savings =  existing costs – proposed costs

\large\ Days\ to\  recover\ price = {\left(\frac{No.\,of\,lamps\times lamp\,cost\,+\,installation\,costs}{yearly\,savings}\right)\times365}

The carbon dioxide emissions calculator is based on:

Natural Gas490
Solar PV (rooftop)41
Hydro Electric24

These values are taken from the 2014 Intergovernmental Panel on Climate Change Life Cycle CO2 Equivalent from selected electricity supply technologies as listed on Wikipedia.

Further reading

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Please Note: Due to other commitments I'm currently unable to spare the time required to answer further questions in the way I'd like. Hopefully this is a temporary situation. I'm sorry for this inconvenience.