The CNET Lounge forum

General discussion

Some basic compact flurescent math

by Owyn / March 1, 2007 12:12 PM PST

Cost of 100w incandescent equivalent CF approx = $1.00
Power consumption of CF bulb = 23W
Cost per kilowatt hour (local) = $.055
Hours of use to save 1 KW = 1000 / (100 - 23) = 13.0 hours
KWh to save $1 = 1.00 / .055 = 18.2

Hours to break even (recover cost of CF bulb) = 18.2 * 13.0 = 236.6

Assuming a bulb was used 4 hours per day then

Days to recover cost of CF = 236.6 / 4 = 59 days (i.e. approx 2 months)

Mileage may vary based on local rates, but, not enough to make a difference. In fact, I would guess that in many cases the break even period would be even lower.

Discussion is locked
You are posting a reply to: Some basic compact flurescent math
The posting of advertisements, profanity, or personal attacks is prohibited. Please refer to our CNET Forums policies for details. All submitted content is subject to our Terms of Use.
Track this discussion and email me when there are updates

If you're asking for technical help, please be sure to include all your system info, including operating system, model number, and any other specifics related to the problem. Also please exercise your best judgment when posting in the forums--revealing personal information such as your e-mail address, telephone number, and address is not recommended.

You are reporting the following post: Some basic compact flurescent math
This post has been flagged and will be reviewed by our staff. Thank you for helping us maintain CNET's great community.
Sorry, there was a problem flagging this post. Please try again now or at a later time.
If you believe this post is offensive or violates the CNET Forums' Usage policies, you can report it below (this will not automatically remove the post). Once reported, our moderators will be notified and the post will be reviewed.
Collapse -
word.
by thriftyT / March 1, 2007 9:05 PM PST

money saved per 1 hour (by using a 23 W CFL vs. a 100W conventional):

(77 W) (1 hr) (1 kW / 1000 W) (0.055 dollars / KWh) = 0.00423 dollars

Therefore, as you said, it would take ~236 hours to save one dollar.

Collapse -
CO2 savings.
by R. Proffitt Forum moderator / March 2, 2007 12:30 AM PST
http://www.google.com/search?hl=en&q=co2+per+kilowatt+hour gives us from 1.5 to 2.3 pounds of CO2 per KWH.

Over your dollar break even analysis of 236 hours lets figure out the CO2 savings.

For the 100W bulb that's 23600 WH or 23.6 KWH or 34.5 pounds of CO2.
For the CFL @ 23W that's 5428 WH or 5.428 KWH or 8.1375 pounds of CO2.

If CO2 is really a concern, then this is a solution.

Bob
Collapse -
Yep. CFL may not be perfect but...
by Owyn / March 2, 2007 5:36 AM PST
In reply to: CO2 savings.

Lot's of reasons to switch to them where possible today. Lower cooling costs in the summer can be another factor.

Another way to save is to switch to higher efficiency, lower noise, better reliability computer power supplies. Anyone purchasing a new system should specify a premium supply. Spending an extra $50 can easily reduce consumption by 100W for a typical new system.

Collapse -
Annual cost of always on 100W load
by Owyn / March 2, 2007 5:47 AM PST

Power used = 365 days * 24 hours/day * 100W / 1000W/KWh = 876KWh
Cost of power = 876 * .055 = $48.18

Collapse -
(NT) (NT) Your calculations are nifty with a touch of rad.
by Pinkmaltese1 / March 3, 2007 3:26 AM PST

Popular Forums

icon
Computer Newbies 10,686 discussions
icon
Computer Help 54,365 discussions
icon
Laptops 21,181 discussions
icon
Networking & Wireless 16,313 discussions
icon
Phones 17,137 discussions
icon
Security 31,287 discussions
icon
TVs & Home Theaters 22,101 discussions
icon
Windows 7 8,164 discussions
icon
Windows 10 2,657 discussions

FALL TV PREMIERES

Your favorite shows are back!

Don’t miss your dramas, sitcoms and reality shows. Find out when and where they’re airing!