Mr. Fantasy (mrfantasy) wrote,
Mr. Fantasy

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Light bulb economics

Let's work this out: I just paid $84.72 for a 12 pack of compact florescent light bulbs for the new chandelier. A 12 pack of incandescent light bulbs from the Home Depot cost $12.74. So you would think I'm $71.98 in the whole.

But, wait. The rated life of the incandescent bulbs is 2000 hours, and the CFLs is 8000 hours. So I'd have to buy 4 sets of incandescents to last as long as the CFLs. So they'll cost $50.96 over the same lifetime. So now the difference is $33.76. (we'll ignore the fact that I'm comparing lots of 12 and will only need 10 for the chandelier--I have to buy them both in cases to get the pricing.)

The most expensive part of this is the electricity. I pay about $0.13/kWh for electricity. A chandelier full of 40 watt incandescent bulbs burns 0.4kW. Over an 8000 hour life that's 3200kWh. At $0.13/kWh that costs me $416 over the life of 4 sets of these bulbs. Over the lifetime of one set of CFL bulbs, which burn 9 watts a piece, or 0.09kW, over 8000 hours, 720kWh, at $0.13/kWh is $93.60.

Total costs of incandescent: $50.96 + $416 = $466.96
Total costs of CFLs: $84.72 + 93.60 = $178.32.

So compact florescent bulbs save nearly $300 over the life of the bulbs. Now, that will probably be 5-10 years, so it's not much per year, but it's real money.

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