How do I calculate cost savings on incandescent bulbs?

[Chris D.]

I want to show my sister some hard facts on how much a 13 watt incandescent (60 watt bulb output) would cost to run for a full 7 day week 24 hours, month, year, ect vs a regular 60 watt bulb..

are there any sites that do conversions?

I'm trying to make her a believer in cutting energy costs..
I saw a 6 pack of 60 watt equlivent 13 watt incandescents for a dam good price at Costco..

any help would be great..
thanks

[NeilBlanchard]

Hi Chris,

I think you mean 13 watt compact fluorescent? It'll be roughly ~22% of the electricity used, or a 78% savings. The cost of buying them has come way down -- my local Aubuchon hardware sells some of them for 99 cents each -- and they take the old failed ones back, to recover the (tiny) bit of mercury in them.

Typically the CFL's last longer than incandescent, though they can't get too hot -- some fixtures that trap the heat will cause them to fail prematurely.

They come in different color temperatures: most people like the warm white best, though cool while or daylight are nice in some situations.

[Daox]

I made a very simple calculator in excel a while back to do some simple calculations like this. In your sister's case, the bulb would pay for itself in two weeks (assuming 10 cents per kWh)! My calculator doesn't include bulb replacement costs, but an incandescent normally lasts 800 hours (a little over 1 month if its never turned off). A CFL lasts on average 10,000 hours (about 14 months if its never turned off). Over a years time, you'd go through about 11 incandescent bulbs and only 1 CFL. So, she would go through $5.50 in incandescent bulbs (if they are around $.50, I dunno, I don't buy them anymore). So, in a year she would save about $45 by replacing ONE bulb. Not bad at all.

Here is my experience with CFLs when I moved into my house. By doing my whole house, they are saving me almost $30 a month and reduced my electric usage by 40%. It cost about $100 to do the whole house. Payback is 3.5 months roughly.
CFLs Lower Energy Usage | EcoRenovator.org

I attached the calculator if you want to play with it. Just fill in the yellowed cells and everything else will populate.

[trebuchet03]

Originally Posted by Chris D.

I saw a 6 pack of 60 watt equlivent 13 watt incandescents for a dam good price at Costco..

any help would be great..
thanks

Do some research on color temperatures.... Maybe spend a few extra dollars to get single packs of a few different ones. A big turn off is going to be if the light color won't play nice with other lights in the house. I think I got 5500K bulbs to play nice with a few incans that can't be replaced cheaply (due to dimmers).

[NeilBlanchard]

Hi,

Ah yes, dimmers -- there are dimmable CFL's though they cost a bit more. If you have a dimmer in the circuit, then you must use a dimmable bulb; even if you leave it on full.

There are also 2-way and 3-way CFL's, I believe; that are for use in these types of fixtures.

[groar]

In my groar's lighting thread - EcoRenovator on EcoRenovator (Ecofriendly DIY Home Projects) I have a spreadsheet to calculate my savings with all my bulb updates.

Don't hesitate to ask questions there,

Denis.