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May. 23rd, 2008 @ 10:35 am Return on Investment
Current Mood: pensivepensive
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So, two halogen lamps of the type we use in the extension cost EUR 7.00 -- EUR 3.50 per piece. They have roughly 1000 hours of operation (it says on the package that they will last a year, if you burn them three hours per day). That comes to EUR 3.50 per lamp per year.
A single warm white LED lamp (with 38 LEDs, so that should give enough light) costs EUR 21. But LEDs have a longer life. If you go by EUR 3.50 of deprecation per year, the lamp will be fully deprecated in 6 years. After that, you're 'earning' money.

So, simply looking at the cost of the lamps, the Return on Investment is at six years.

But wait! The halogens draw 50W, while the LEDs draw 2.1W! Let's do some calculations with that...
We have fourteen spots in the extension. Suppose we do run the lights for three hours every night for a year. And suppose we pay EUR 0.20 per kW/h.

14 * 50 W = 700 W. 700 W / 1000 = 0.7 kW. 0.7kW * 3h =2.1 kW/h. 2.1 * 20 = EUR 0.42 per night. For a year, that makes 0.42 * 365 = EUR 153.30.
So, using the halogens costs us EUR 153.30 per year (if all of the assumptions are correct, of course. But these being assumptions, we assume them to be correct anyway. ;) ).

For the LEDs:
14 * 2.1 W = 29.4 W. 29.4W / 1000 = 0.0294 kW. 0.0294 kW * 3h = 0.0882 kW/h. 0.0882 * 20 = EUR 0.01764 per night. For a year, that makes 0.01764 * 365 = EUR 6.44.

The difference between using LEDs and halogens is thus a whopping EUR 146.86 in electricity costs! That makes a cost reduction of EUR 10.49 per spot, which means that the break-even point, seen from the cost of electricity alone, is almost exactly after two years.
The third year, we'd be seeing a cost reduction of EUR 146.86 + (EUR 3.50 * 14) = EUR 195.86. And if we do an conservative estimation and assume that the LEDs will have an operational life of 10.000 burning hours, that means a total cost reduction of EUR 1566.88 during the life of the LED lamps.
Of course, that assumes the price of electricity stays constant -- which is doubtful to say the least.

I think I'll be ordering a few of those LED lamps to see if they can replace the halogen lamps... With a RoI of two years, that is certainly a worthy investment.

Also, feel free to point out any miscalculations I may have made!
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Date:May 23rd, 2008 09:11 am (UTC)
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wow... does this mean that LEDs are also more power efficient then your regular spaarlamp? Just think if the whole of the Netherlands would shift to using LED's that'll save quite a lot of energy over the span of just one year.
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Date:May 23rd, 2008 10:30 am (UTC)
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does this mean that LEDs are also more power efficient then your regular spaarlamp?
That depends on what you mean with 'power efficient'. Yes, they consume less current -- but if you want the same amount of light, it might not be that good of a deal. Also, LEDs have a rather narrow beam, which makes them well suited for desk lamps, but not much so for ambient lighting.
The spaarlamp equivalent of a 60W lightbulb is only 12W -- that is a tremendous savings already.

The best feature of LEDs is their long life. Which is why you see more and more traffic lights that use LEDs -- swapping out the bulbs near the end of their life-cycle costs more than the bulb itself. If you use LEDs, you don't have to swap 'em out for many, many years to come, which decreases the time needed to earn 'em back dramatically.

I think it's important to do the math on a case-for-case basis, and to see if LEDs are suited for a particular application. Blindly swapping everything for LEDs will not give the desired results.
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