Question

What type of light bulbs should I use? I'm looking for ways to reduce the energy I use for lighting (without resorting to candles!).

Asked by Evan
Findlay, OH

I leave the lights off unless absolutely necessary, and I try to use sunlight when I can. I'm looking for cost-efficient light bulbs.

Answer

David Bergman

Answered by David Bergman

New York, NY

David Bergman Architect

May 7, 2011

I’ve been talking a lot lately about ecodesign and ROI, or return on investment.

  • Some of us will pursue ecological improvements even if the numbers don’t add up, feeling (with good reasoning) that there’s more involved here than simply saving money on utility bills.
  • Others of us, though, may not have that financial luxury (or, you might say, that commitment -- but let’s not get judgmental here).

Lifetime costs vs. first costs

When the decisions come down to strict bottom lines, we also need to factor in long-term versus upfront costs.

That, too, may be difficult if you don’t have the financial wherewithal to incur those first costs while waiting to reap the benefits over the coming years.

  • This was somewhat less of an issue when our lighting choices were basically between incandescents -- which I’ve referred to as glorified toasters elsewhere on GreenHomeGuide -- and compact fluorescent bulbs.
  • While the CFLs were several times more expensive than the soon-to-be obsolete Edison-era toasters, it wasn’t too difficult to figure out that, if you spent a few dollars more at the hardware store, you‘d more than get that back within a few years.

LEDs have much greater first costs

But the new generation of light sources -- I’m talking mainly about LEDs here -- push the calculations out further.

  • Yes, they are a lot more expensive than 99-cent incandescents or $8-per-fourpack CFLs. (The difference in cost between those two options, you may recall, used to be a lot more.)
  • An “inexpensive” LED might run $30 or $40 or more, which actually seems almost a bargain compared to the prices a mere year ago.

Calculating the ROI

How can LEDs be the cost-effective choice? We need to do the math. (Skip the Barbie “math is hard” references, please.)

  • First there’s the fact that the pricey-at-first LED should last 30 to 40 times longer than an incandescent, and 4 to 5 times longer than a CFL.
  • So right off the bat, the prices begin to equalize. 40,000 hours equates to around 40 incandescent bulbs, maybe five CFLs, or one LED.
  • And that’s without factoring in the headache -- not so minor if you have high ceilings -- of changing burned-out bulbs.

But on to the bigger savings: electricity bills.

  • Let’s say we’re talking about 60-watt-equivalent output light sources. (I’m using 60-watt here because the brightest LEDs currently available max out at around that brightness.)
  • Those 40 incandescent 60-watt bulbs will consume around 2,400 kilowatt-hours over their lifetime.
  • The equivalent CFLs will consume about a quarter of that amount, say 600 kWh.
  • The LED, at around 8 watts (some are lower, some are higher) will use just half of that, or 300 kWh.

So your total costs over 40,000 hours will look something like this (based, for simplicity, on 10 cents per kilowatt-hour -- it’s a lot higher here in the northeast):

  • 40 incandescent bulbs: $40 in bulbs plus $240 in electricity = $280
  • 5 CFLS: $16 in bulbs plus $60 in electricity = $76
  • 1 LED: $30 for one bulb plus $30 in electricity = $60

Or compare bulbs on their cost over a year's time

If looking at a 40,000-hour horizon seems a tad too far away, it may be a little easier to look at this in terms of costs per year.

  • Let’s say you use the light for an average of three hours per day. That would come to about 1,100 hours per year.
  • To keep things simple (OK, relatively simple), let’s call that 1/40th of the 40,000 hours lifetime we used above (which, by the way, also implies that that LED might last 40 years at that rate of usage!).
  • So a year of light from an incandescent bulb, including the amortized price of the bulbs, costs about $7.
  • A year using a CFL would be about $2, and for that LED it would be a whopping $1.50.

You can play with these numbers a bit: bulb prices, lamp life, and electric rates will all vary, but this gives us a reasonably good picture. Incandescents are the big losers, CFLs are a big improvement, but the prize goes to LEDs, especially as their cost goes down further.

When you combine these numbers with other observations about CFLs (there’s that pesky mercury problem), you can see why a lot of us refer to CFLs as a transitional solution. LEDs, if you can swallow that upfront cost, make sense for a lot of applications today and will only become more attractive, along with their OLED brethren, as their cost goes down and their efficiencies continue to climb.

Candles?

About that alternative you mention of using candles: don’t do it.

It may decrease your electric bill, but if you add up all the actual AND environmental costs, candles trail all three of our electric options. Plus it’s hard to find a 60-watt candle. 

Tagged In: cfl, led

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