We recently learned that one LED light can save you money and cut your CO2 emissions. Question is… what happens if we replace ALL the lights in our house with LED lights? Glad you asked. I calculated a few numbers for you and put the results into some handy tables and graphs. But first, a little bit of background info is required.
According to an interesting blog post by a lighting company in Florida, the average house has 47 light bulbs. So we’ll look at numbers for three different sized houses: a small house or apartment (24 bulbs), a typical family home (47 bulbs), and a typical McMansion (94 bulbs). Like last time, we will also see how using solar power stacks up against coal.
Some other assumptions include the price of power and the amount of CO2 made. For this post I have assumed that the cost of power is $0.11 per kilowatt hour, which is what I pay for 100% wind energy. The national average is about $0.12 per kilowatt hour. The price of energy may go up in the near future, which would make the estimates I show you below pretty conservative.
The amount of CO2 produced by coal is 909 grams per kilowatt hour, and 105 grams per kilowatt hour for solar. These values comes from BlueSkyModel.org, and are pretty comparable to other estimates I’ve seen.
The cost of the bulbs I use are pretty standard; although I’m sure you could find them cheaper without trying too hard. Three prices for LED bulbs are given, $7.99 (current price), $5 (sale price), and $1.78 (same as CFL). I used the optimal lifespan of incandescent and CFL bulbs when comparing to LEDs, which is highly unlikely, but it makes the numbers shown below even more conservative (again!).
The costs are calculated over 10 years, even though most LED bulbs should last longer under normal use. Ten years seemed like a nice handy number for comparisons.
We are going to look at…
- the cost of the electricity alone
- the cost of replacing all of your incandescent bulbs with CFLs or LEDs
- the cost of power and bulbs over 10 years
- and the total amount of CO2 produced by using either coal or solar energy to power your bulbs.
Cost of Power
This table shows how much energy a 60 watt incandescent uses, versus a 14 watt CFL, and a 10.5 watt LED. At these wattages these bulbs should put out about the same amount of light. All bulbs are assumed to be on for only 30 minutes a day. In reality, some bulbs will be on most of the day (porchlight), some for a few hours (living room/kitchen), and some every few days (storeroom, closet, etc.). Thirty minutes seemed like a good compromise.
Now that we have some idea of the power we are using, how much does it cost? If we know how much power is used, and we assume power costs $0.11 per kilowatt-hour (1,000 watts used in an hour), then we can figure out the cost.
Looks like LEDs are the cheapest to use, because they use the least power. Makes sense.
Cost of Bulb Replacement
Now we want to see how much it might cost if we decided to replace all the incandescent bulbs in our house with CFLs or LEDs. I give you three different prices for LEDs as outlined above.
Now we might want to know how many replacement bulbs we’d need to buy over 10 years. We would not need to buy any LEDs because they last longer than 10 years, however we’d have to buy quite a few incandescent bulbs. As for CFLs, I assumed that, even though at 30 minutes a day we would not exceed the lifespan of a bulb over 10 years, we would need to replace bulbs at least once.
This is a pretty reasonable assumption because the light output of CFLs drops quickly within a few years, they are finicky with respect to fluctuations in power, can’t be turned off and on quickly without shortening their life, and are almost as fragile as incandescent bulbs. LEDs have none of those problems. Bulb lifespan data comes from wikipedia.
Cost of Power Plus Bulbs
So now we can add it all up to see the least expensive alternative overall. Of course, CFLs and LEDs beat incandescent bulbs easily. If you bought your LEDs on sale, CFLs would still be a bit cheaper. However, we are not counting all the problems with CFLs that we mentioned already. Also, when the price of LEDs drop, as they will over the next few years, then LEDs will become the price leader.
Carbon Dioxide Produced
Now many of us are concerned about how much CO2 we make and it’s affects on our own, our children’s, and our country’s future. Powering incandescent bulbs with coal energy produces 10,292 pounds of CO2 over 10 years for an average house with 47 bulbs. Just think of every house in America pumping out this much CO2 for the past 100 years, give or take. That’s an obscene amount of CO2!
If you switch to CFLs or LEDs your CO2 output drops dramatically. BUT… as you can see, if you use solar power your CO2 production drops way down!
I was totally surprised that the type of power you use has a bigger effect than the type of bulb you use. Looking at the red-outlined boxes, 94 coal-powered LED bulbs makes 150% more CO2 than 94 solar-powered incandescent bulbs. BUT, 94 coal-powered incandescent bulbs make 865% more CO2 than powering those same incandescent bulbs with solar power. So switching to solar or other alternative power has the greatest effect. Wow!
The Bottom Line
The figure below summarizes the discussion above, and shows us that we will save a lot of money by using CFLs or LEDs.
The next striking figure shows us how much carbon dioxide we make using different bulbs and power sources. You can easily see that using solar power makes a HUGE difference; much more of a difference than the type of bulbs.
So here’s the bottom line…
- If you want to save money… switch to CFLs and LEDs
- If you want to save the environment… switch to alternative energy, like solar or wind.
- If you want to do BOTH… install CFLs and LEDs –AND– switch to alternative energy.
Here in Texas we have lots of wind power. My power company sells me 100% wind energy, which is pretty comparable to solar. So if you live in a state where you can get solar or wind power, do it! You’ll be doing yourself, your family, and the world a big favor.
Next time…
The long-awaited article on the affects of climate change on your allergies is in the works. Just to give a little teaser, did you know that the pollen season for ragweed has INCREASED by over twenty days in the upper midwest? And that’s just over the past 30 years. That is hard, directly observed, irrefutable evidence of climate change. So come back next week if you want to know more.
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