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Energy Cost Savings Calculation


Analysis of Energy and Cost Savings

There is no doubt that changing to energy saving light bulbs will save you a large amount in electricity but here we set out exactly how much you could save. The amount of the saving will differ dependent on whether you move to Halogen, compact fluorescent lamps (CFLs) or at best LEDs. Initially we will look at a comparison of these 3 types of bulb against the standard filament light bulb. The table below looks at a typical 60w filament incandescent light bulb and shows the percentage saving when contrasted to the Halogen, CFL and LED bulbs.
Lamp Technology Power Consumed in Watts Light Output in Lumens % saving over Incandescent
Incandescent/ Halogen 60 watts 750 lm 0
Halogen Energy Saving 50watts 750 lm 17%
CFL 14 watts 750 lm 76%
LED 7 watts 750 lm 88%

Now clearly there is a massive saving from moving say from standard incandescent light bulbs to LEDs but the saving will be less if you are just moving from CFL or fluorescent lamps to LEDs which is around 55%.
The electricity savings are very significant but there are addition benefits in terms of environmental sustainability through reducing your carbon footprint. On average the generation of 1kWh of electricity creates 0.47kg of CO2 so the positive impact is high.

Electricity Usage Costs

You might be saving 88% by using LEDs but it is important to know exactly how much that will mean in pounds sterling. In order to work out the costs we will look at a household that has lights on for 6 hours each day and pays 13p/KWhr for electricity. The table below shows the costs for a single 50w and 100w bulb together with the calculated costs for 20 bulbs.

Number of Lamps Wattage of Lamps Annual cost of Electricity
1 50 £14.24
1 100 £28.47
20 50 £284.70
20 100 £569..40

I am sure you will agree that these costs are very high so we now need to look at how much you can actually save

Electricity Cost Saving Calculation

Here we look at the same 50 and 100 watt bulbs which are on for 6 hours a day but now compute the electricity cost savings from moving to Halogen, CFL and LED bulbs.

Number of Lamps Wattage of Lamps Halogen Saving CFL Saving LED Saving
1 50 £14.24 £11.10 £12.53
1 100 £28.47 £22.21 £25.05
20 50 £284.70 £222.07 £250.54
20 100 £569.40 £444.13 £501.07

The above table shows the true magnitude of the savings so for example if you have twenty GU10 50w halogen spots in your kitchen you stand to save a massive £250.54 per year in electricity!!!
However this is still not the total story because we need to take into account the cost of the LEDs because they are quite expensive but also accommodate for the fact that they last around 30 times longer than standard halogen or filament bulbs.

LED Investment Analysis

In order to get a full picture of the savings it is generally best to compute the savings over the lifetime of the LEDs but take into account the costs of the bulbs over that lifetime. The table below now adds in the total lifetime saving you will make from moving to LEDs, the payback time for your investment and the subsequent amount you will save annually.

Number of Lamps Wattage of Lamps Lifetime Saving Payback Time in Years Subsequent Savings per Year
1 50 £228.60 0.4 years £16.69
1 100 £407.20 0.5 years £29.73
20 50 £4572 0.4 years £333.76
20 100 £8144 0.5 years £594.51

This really puts it into perspective with the analysis showing that by changing the twenty 50w GU10 spots you can potentially save a massive £4572 over the LED life in this case of 13.7 years and you will get payback for your investment in as little as 5 months.

Free Energy Survey

If you would like an actual calculation to be made for your specific project or home then please get in touch for the SLB Free Energy Survey

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