You're probably expecting the usual fluffy "how to" article - the sort that opens with a few insipid generalisations before meandering into a less than thunderously convincing argument vaguely related to the title. If so, prepare to be disappointed/pleasantly surprised (delete as appropriate); I have neither the time nor inclination and frankly the data speaks for itself. So let's pitch in and start doing some math.
A typical mains powered halogen lamp (as commonly found recessed into ceilings) consumes 50 watts, can be purchased for about 2, lasts up to 2,000 hours, and will cost 12 to run for those 2,000 hours. The running cost is worked out using the standard rate of 0.12 per kWh and assumes modest average use of 3 hours per day which equates to roughly 1,000 hours per year.
A GU10 LED replacement (i.e. an LED with near identical performance characteristics, such as the Sharp Zenigata) consumes 4 watts, costs at present 24 to buy, has an effective lifespan of over 40,000 hours and will cost 0.96 to run over the same time period.
Initially then it seems that the LED is the more expensive option thanks to its greater purchase price. But this picture requires a bit more "real world" context to reveal the truth.
For a start, the longevity of the LED is such that the halogen lamp will need to be replaced 20 times - that's 20 x 2 which means that the purchase costs (plural) for the halogen are in fact 40 against 24 for the LED.
Additionally, if instead of comparing the two over the rather unimpressive lifespan of the halogen we use that of the LED (40,000 hours) then the LED costs 19.20 to run whereas the halogen lamp is a whopping 240.
Finally, let's add back in the "real" purchase price differential and over 40,000 hours it looks like using halogen lighting costs us 280 whereas the equivalent LED instead costs 43.20. We're way beyond projected savings of 10%, 20% or even 50% - the running costs of halogen lighting are over 1000% more than comparable LED lighting.
Even with the initial investment figures added back in, halogen lighting is easily 700% more expensive. Interestingly also, in this example the LED actually costs less to run than to buy. The halogen lamp is superficially cheap to buy (but as we saw ends up costing nearly twice as much as the LED due to constant replacement costs) yet hugely expensive to run. It's a totally different ball game.
Of course, this is a very scaled down example applied to one little-used light bulb. I have just walked from my North facing kitchen where 10 down lights are almost permanently on from 7:00 A.M. to midnight, thru a hall with little natural light and 4 more halogen lamps, into my office where a further 6 glow maybe 6 hours a day.
Adding up the total for just these 3 rooms produces an alarming annual figure of 100,000 hours in total. That's worked out as: 10 * 17 hours plus 4 * 17 hours plus 6 * 6 hours all times 365 days. In financial terms it comes out as: 100,000 hours * 50 watts * 0.12 all divided by 1000 (we want kilowatt hours) which is 600. Or at least it does for halogen lamps; the LEDs come in at a more modest 48 per year.
If we look at real life examples such as shops, offices, hospitals, hotels, airports and so on, where it is commonplace to use artificial light almost all the time then things get really interesting. Economics is little more than mathematics with currency symbols, and if we extrapolate our simple calculations above the numbers start to resemble seriously big bucks.
We have demonstrated that, despite initial appearances, the purchase price of an LED is about half that of an equivalent halogen lamp when you account for the repeat-purchases as it wears out. We have also calculated that overall electric lighting using halogen lamps is 12 times more costly than replacing them with LEDs. So the one question remaining then is this: why would anyone stick with halogen lamps?
A typical mains powered halogen lamp (as commonly found recessed into ceilings) consumes 50 watts, can be purchased for about 2, lasts up to 2,000 hours, and will cost 12 to run for those 2,000 hours. The running cost is worked out using the standard rate of 0.12 per kWh and assumes modest average use of 3 hours per day which equates to roughly 1,000 hours per year.
A GU10 LED replacement (i.e. an LED with near identical performance characteristics, such as the Sharp Zenigata) consumes 4 watts, costs at present 24 to buy, has an effective lifespan of over 40,000 hours and will cost 0.96 to run over the same time period.
Initially then it seems that the LED is the more expensive option thanks to its greater purchase price. But this picture requires a bit more "real world" context to reveal the truth.
For a start, the longevity of the LED is such that the halogen lamp will need to be replaced 20 times - that's 20 x 2 which means that the purchase costs (plural) for the halogen are in fact 40 against 24 for the LED.
Additionally, if instead of comparing the two over the rather unimpressive lifespan of the halogen we use that of the LED (40,000 hours) then the LED costs 19.20 to run whereas the halogen lamp is a whopping 240.
Finally, let's add back in the "real" purchase price differential and over 40,000 hours it looks like using halogen lighting costs us 280 whereas the equivalent LED instead costs 43.20. We're way beyond projected savings of 10%, 20% or even 50% - the running costs of halogen lighting are over 1000% more than comparable LED lighting.
Even with the initial investment figures added back in, halogen lighting is easily 700% more expensive. Interestingly also, in this example the LED actually costs less to run than to buy. The halogen lamp is superficially cheap to buy (but as we saw ends up costing nearly twice as much as the LED due to constant replacement costs) yet hugely expensive to run. It's a totally different ball game.
Of course, this is a very scaled down example applied to one little-used light bulb. I have just walked from my North facing kitchen where 10 down lights are almost permanently on from 7:00 A.M. to midnight, thru a hall with little natural light and 4 more halogen lamps, into my office where a further 6 glow maybe 6 hours a day.
Adding up the total for just these 3 rooms produces an alarming annual figure of 100,000 hours in total. That's worked out as: 10 * 17 hours plus 4 * 17 hours plus 6 * 6 hours all times 365 days. In financial terms it comes out as: 100,000 hours * 50 watts * 0.12 all divided by 1000 (we want kilowatt hours) which is 600. Or at least it does for halogen lamps; the LEDs come in at a more modest 48 per year.
If we look at real life examples such as shops, offices, hospitals, hotels, airports and so on, where it is commonplace to use artificial light almost all the time then things get really interesting. Economics is little more than mathematics with currency symbols, and if we extrapolate our simple calculations above the numbers start to resemble seriously big bucks.
We have demonstrated that, despite initial appearances, the purchase price of an LED is about half that of an equivalent halogen lamp when you account for the repeat-purchases as it wears out. We have also calculated that overall electric lighting using halogen lamps is 12 times more costly than replacing them with LEDs. So the one question remaining then is this: why would anyone stick with halogen lamps?
About the Author:
Louisa Kennicot highly recommends these additional articles about both GU10 and MR16 LED applications specifically and also 12v LED spotlights in general.
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