ER Project House: CFLs Installed – Energy Usage Down 40%

by Tim Fulton on October 28, 2008

I’m going to spare you and not go through an in depth installation on how to screw in a light bulb.  However, I am going to talk about how simply installing CFLs dropped my electricity useage by 40% in one month despite it being fall and the days growing shorter and the heat being turned on for the first time this fall.

In September we used 428 kWh of electricity in 21 days.  For comparison’s sake I’m going to extrapolate that number up to 591 kWh for 29 days so it is the same as the next bill.  This is how we moved into the house.  There were CFLs in some areas, and many areas with normal incandescent light bulbs.

Around the beginning of the next month I went through the house and replaced probably 90% of the bulbs with CFLs.  That bill came not too long ago.  This bill was for the past 29 days.  It showed a very nicely improved upon 355 kWh.  Yep, that is a 40% reduction in electricity useage!

Now, there are actually several important things to keep in mind here.  First off, we use normal conservation tactics like keeping lights off in rooms we weren’t in and that sort of thing.  Our water heater is natural gas, so hot water isn’t figured into this.  The days are getting shorter and lights need to be on longer than last month.  We didn’t have the heat on in the first month’s bill, but did on the second month’s bill.  This includes one room with electric in floor heat and gas forced air although it wasn’t on much.

Now, whats the damage to the pocketbook for doing an 90% bulb replacement?  Well, it honestly wasn’t too bad at all.  I paid right around $100 to do most of the house.  I was able to find a four pack of 15W bulbs (60W equivalent) for $4 and grabbed a few packs.  The ones that hurt were the dimmable bulbs and the few special bulbs.  The dimmable bulbs came in packs of four as well, but they cost $15 per pack, and I needed four packs.  The other ones that add up fast were special bulbs like ones with candelabra bases and ones with a plastic bulb shell for a lamp shade to clamp onto.  But, if we look at the pay back time, we are still looking at just a few months.  These bulbs are saving me almost 240 kWh per month!

Materials list:

  • Assorted CFL light bulbs – $100

Total: $100

Energy Savings:  ~240 kWh

Payback: 3.5 months (at $.12 per kWh)

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November 24, 2008 at 9:50 am


1 Lea February 2, 2010 at 11:49 am

These things are horrid. I suppose if electricity gets SO expensive that I MUST use them, then I will do what I have to do. But, my husband replaced every bulb in our home with these and when first switched on, they are so dim! And, they contain mercury.

I stocked up on 40W and 60W at the dollar store. I’m good.

2 Mike September 25, 2010 at 8:42 pm

Here in NZ, household lighting amounts to approx 7 – 10% of total household energy costs, these CFLs use 75% less power than same output filament lamps, so you will save 75% of 10% = 7.5% at best. Not sure how you managed 40% ??
We replaced all the lamps in our house that remain on for more than 4 hours each night with CFLs about 2 years ago, to date they have all failed and had to be replaced, they just dont last as long as claimed on the box, resulting in no real cost saving. ie they are a waste of time.

Mike NZ

3 Tim Fulton September 27, 2010 at 8:23 am

Sorry to hear you’ve had bad luck with the CFLs. I’ve had a couple failed ones, but not many at all.

Obviously, lighting is a much larger percentage of my bill than your bill. That is how I achieved a 40% reduction.

4 Kevin December 14, 2013 at 12:47 am

Lea, unfortunately all bulb manufactures are not created equal. Even models from the same company can have greater differences. I purchased the cheapest bulbs from one of the local big box stores here and they have worked great. Virtually instant on with no dim starts. I am also very sensitive to flickering and I’m always the first to mention it in a light, be it a fluorescent or those led Christmas lights. These don’t have the slightest bit of perceived flicker. I have however have experience with some other brands, most more expensive too that take minutes to warm up and also flicker. Talk about annoying. Cold temperatures can also aggregate the problem. I live in Canada, so forget using these outside unless they are in a heated box.
If the bulbs are well manufactured they can also last quite long and are much more resilient to power fluctuations that incadescents. I first switched when I was living in a apartment building in a town. Wiring probably wasn’t the greatest(visible issues elsewhere) and I constantly had to change the light bulbs on average about every 4-5 months. I didn’t care about the cost but when you go to turn on a light and the bulb flashes and goes dark, well you turned on the light for a reason… I replaced them all with CFLs and never had to replace a single one in the remaining two years I was there.
Given the right bulb (quality and preceded colour), CFLs can be replaced without noticing a difference(unless looking directly at the bulb). However given the wrong bulb(wrong color,slow start and flickering), I’d much rather go to using candles(can’t stand flicker).

Tim, great article. Although its now been a few years, I’m still talking to some about the benefits of CFLs. Want to trade power bills? In wish I could say the majority of my power bill is lighting. I’ve got a 260w yard light that is constantly on(even during the day, broken sensor) and although its costing me alot , my heating bills are astronomical in comparison. Its a recently bought house so I’ll be doing some reinsulating for sure(and replacing all inside lights with CFLs).

Oh one last thing since this comment is already long, It should be noted that some cfl bulbs have horrible power factor. Basically what that means is although they only draw say 15w but has a 0.5 of rating, the utility company has to generate the equivalent of 30watts to power the light bulb. Some power companies will charge a premium because of this, others will ignore it unless they are drawing a huge load (industrial customers).

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