Monday, January 25, 2010

Cost benefit analysis of energy efficient bulbs

We’ve had six GU10 bulbs in our kitchen for a while now and I’ve never really been very happy with them. They swallow a lot of power, don’t seem to last very long and are pretty expensive to replace. I got hold of an LED replacement some time ago and was less than impressed. It didn’t produce enough light, was really really expensive and then died after a couple of months. So when I popped into Maplin at the weekend, I thought I’d try out their low-energy GU10 replacement. Admittedly these are even more expensive than the full powered version, but they claim to last for 8000 hours and use a lot less power. I’m happy with the amount of light they throw out, although they suffer from the usual problem of taking a while to warm up. Anyway, I thought I’d do a quick calculation of how long it would take me to earn back the money I shelled out for them.

Cost per KWH – 0.15

Old 6 bulbs @ 50W = 300W

New 6 bulbs @ 11W = 66W

KWHs saved = 0.3-0.066 = 0.234 KWHs

Cost of bulbs = £7.49*6 = £45

Number of KWHs required to cover cost = 45/0.15 = 300KWHs

Number of hours required to cover cost = 300/0.234 = 1282 hours

Assuming 5 hours use a day = 1282/5 days = 256 days = 8.5 months

So based on this very rough calculation and assuming I’ve calculated it correctly, this would appear to be a good deal. Fingers crossed they actually last for as long as claimed, which I’m reasonably confident about based on my experiences with other energy efficient bulbs.

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