Category — light bulbs

Dear Mr. Energy,

My dad and I are in a disagreement. He says that it uses more money and energy to turn on the fluorescent lights in our car repair shop than it does to simply let them run all night, and I think he’s nuts. Who’s right?

–Suffering Son in Sanford

Dear Suffering,

The truth is that you and your dad are both right. Kind of.  Fluorescent lights actually do draw more energy when they’re first turned on than it takes to keep them on, but this only really matters if you’re going to have the light on a very short time. After a couple of minutes the difference is moot. In the case of a place of business that doesn’t need its lights on all night, it is significantly more energy efficient to turn the lights off than to leave them on. This applies to both the long, traditional fluorescent lights like the kind you probably have in your shop as well as to compact fluorescent lightbulbs, which are just a different form of the same technology.

Replacing regular lightbulbs with compact fluorescent lightbulbs (CFLs) is supposed to help you save money and energy. They’re more expensive than conventional (incandescent) lightbulbs, however, and due to their mercury content you can’t just throw them away when they break. According to the CFL makers, CFLs last 10 times as long as a conventional bulb, although based on personal experience I’d say that’s an overestimate.

We use mostly CFLs in our house and we’ve had some quit working after only a couple of months; while others have been working as long as we’ve owned our house: 3 years. Apparently there are ways to extend the life of CFLs, like keeping them on at least 15 minutes at a time and only installing them in areas where the temperature will stay constant, but while it’s possible to only install them inside at our house, keeping them on 15 minutes at a time is often impractical. Think about it: do you spend 15 or more minutes in the bathroom every time you go in there?

Hey – and if you buy a bulb and it quits working earlier than it should, return it! This requires keeping your receipts, of course, and having an idea of which bulb goes with which receipt, which for many people (like me) is a pain, but IF you are good at that sort of thing then you should be able to get your money back, or at least another bulb, depending on the place you bought it.

But let’s say that we’re accepting that CFLs do last 10x longer than conventional bulbs. We’re all using them optimally and we didn’t get any bum bulbs from the manufacturer. Using my house as an example, I’ll do the math. Please keep in mind that everything in my little word problem is an estimate, from cost of bulbs to time saved to energy cost savings. But if I calculate it right I should be able to figure out if it’s really worth it, financially, to replace all your conventional bulbs with CFLs.

# of lightbulbs needed: 60 (our house is about 2500 sq. feet and we have overhead light fixtures in every room plus various lamps, etc. 

cost of conventional bulbs: $1/ea, so $60

cost of CFLs: $7/ea, so $420 (I’m using the CFL currently in my desk lamp as an example of a typical bulb: it’s a 13 watt, 120 volt medium screw)

energy savings for each CFL (according to the pamphlet my energy company, Central Electric Membership Corporation, sent us): $4.80/year, or $36 over the lifetime of the bulb. This means each bulb should last 7+ years! If we accept that CFLs last 10x longer than conventional bulbs, this means we’d have to replace our conventional bulbs 10 times in the 7 years we have our CFLs, so…

replacement conventional bulbs over the next 7 years (7 x 10 years x $60 worth of bulbs) = $420

So we’re even in terms of cost.

Add in the energy savings (60 bulbs x $36/ea) and I get $2160 in savings over the next 7 years, or $300 year. Then add in the $.50 credit that our electric company gives us for each bulb, and we get $2190 in savings over 7 years.

That is not too shabby. And even if the industry claims are grossly exaggerated, say, by half, then it’s still over $1000 in energy savings over a 7-year period.

It all adds up, doesn’t it?