[This just in on May 13: I majorly screwed up yesterday’s calculations causing the embodied energies of the steel to be over-estimated by a factor of five and therefore throwing this whole post off. Ugh. So sorry. The argument is not as straightforward as I had hoped and I will have to look into it more for the future. I’m afraid I’m back, for now, to being unclear about the embodied energy versus energy saved balance. Anyway, this post and its conclusions are, for now, unreliable.]
Fair warning: there’s going to be a lot of math in this post, so if you just want to get the gist, skip to the bold bits in the middle and at the bottom.
We’d all like to think that if you walk into a store and see a washing machine that uses 20% less electricity than the one you have at home–yippee!–you get to buy yourself some new home gadgets and at the same time do the environment a favor.
The problem is that the appliance you’re thinking about requires a lot of energy to manufacture–“embodied energy.” Plus, you have to factor in the habitat damage caused by mining the metals, the water pollution caused by smelting them, the energy of transportation of the appliance and on and on.
Of course, if you’ve already decided to buy a new appliance, it’s best to buy the most energy-efficient model. The question is–and it’s a complicated one–is there ever a time when it’s actually better to buy a new appliance than to keep an old one that works perfectly well?
That’s the question the New York Times tried to answer on Sunday with its story “If Your Appliances Are Avocado, They Probably Aren’t Green,” by Alina Tugend. According to the story:
“It takes energy to make a product,” said Noah Horowitz, senior scientist at the Natural Resources Defense Council. “You don’t want to replace perfectly good products.”
He gave me his rule of thumb for refrigerators.
“If it’s avocado or brown-colored, it’s time to retire it,” he said. Refrigerators from the 1970s, the last time I believe those particular appliance colors were in vogue, use three to four times the power of today’s models.
A spokeswoman from the Environmental Protection Agency, which oversees the Energy Star program along with the Department of Energy, told me that, generally, any appliance over 15 years old probably should be put out to pasture.
Tugend then goes on to write:
“It turns out that clothes washers and dishwashers have pretty much the same criteria as refrigerators — they have become much more energy-efficient. So if yours is inching toward 15 years, consider replacing it.”
And while she’s right about the 15-year-old fridge–replace it–it turns out she’s wrong about about the 15-year-old dishwasher and laundry machine–use them till their dying breath.
Because, as you’ll see below, only in the case of the refrigerator do the energy savings outweigh the embodied energy and other environmental impacts of manufacture (not to mention the impact of disposing of the old appliance).
To figure this out, I noodled around the internet but was unable to find studies giving the embodied energies of even a single appliance (if you know of a source for embodied energies of appliances, please email me or leave behind in comments).
What I did find, though, is a Australian government study on solid waste management that gives the weights of different materials in a variety of average appliances (154 pounds of steel, for example, for a refrigerator, 55 pounds of steel for a dishwasher, and 33 pounds of steel for a laundry machine). I also found this Tufts University web page which gives a range of values for embodied energy of the production of steel, the major material in most appliances (I’m taking a figure of 40MJ/kg or about 25 kilowatt-hours [5/13: should be 5 kilowatt-hours and that figure should follow throughout] per pound of steel).
In other words, according to these figures, the embodied energy of the steel alone in an average refrigerator is:
154 lbs x 25 kWh/lb = 3,850 kWh.
The embodied energy of the steel in a dishwasher is:
55 lbs x 25 kWh/lb = 1,365 kWh.
And the embodied energy of the steel in a laundry machine is:
33 lbs x 25 kWh/lb = 825 kWh.
If my figures and math are anything near correct, to make it worth replacing your old appliances with new ones, those are the amounts of energy you would have to save, just to recoup the energy used to produce the steel. This, of course, doesn’t include the energy of the other materials in the appliances or of the energy of the manufacture or distribution of the appliance itself. The actual embodied energy of each appliance is likely much higher than the figures above.
Now, considering refrigerators, today’s models use about half the energy of a 15-year-old model, according to the American Council for an Energy Efficient Economy (the ACEEE). Since, according to the Consumer’s Guide to Effect Environmental Choices (a book), today’s average refrigerator uses 1,100 kWh per year (suggesting that a 15-year-old model uses 2,200 and that the annual energy savings would be 1,100 kWh per year).
In other words, recouping the embodied energy of the steel alone in a new refrigerator when replacing a 15-year-old refrigerator would take:
3,850 kWh / 1,100 kWh per year = 3.5 years (this means, to be explicit, that the energy savings of your new fridge would have to pile up for 3.5 years before it equals the energy costs of the steel in the fridge you bought).
On the other hand, according to the ACEEE, a modern dishwasher only uses 30% less energy than a 15-year-old one. Since a dishwasher according to the Consumer’s Guide, only uses 299 kWh a year, that means a new dishwasher would save only only 90 kWh a year.
In other words, to recoup the embodied energy of the steel alone in a new dishwasher by replacing a 15-year-old dishwasher would take:
1,365 kWh / 90 kWh per year = 15.2 years.
Considering, finally, the laundry machine, the ACEEE doesn’t seem to offer a energy efficiency comparison to older models, but I’ll assume a 30% improvement over 15 years, the same as for dishwashers. The average laundry machine, according to the Consumer’s Guide, uses only 99 kWh a year, which means a new laundry machine would save only about 30 kWh a year.
In other words, to recoup the embodied energy of the steel alone in a new laundry machine by replacing a 15-year-old laundry machine would take:
825 kWh / 30 kWh per year = 27.5 years.
What does all this mean? Well, first of all, let’s be clear that the sources of my figures aren’t the best and that I’m not a manufacturing analyst and that this analysis should be regarded more as a thought experiment than anything else. On the other hand, since all we’re considering is the embodied energy of the steel content of the appliances, it would likely actually take more than the estimates I’ve made to recoup the energy of the new machines.
Regardless, what I conclude is that, if environmental impact is your chief concern, than your best bet is to keep using all but your most energy intensive appliances until they wear out.
In other words, when it comes to residential dishwashers, laundry machines, vacuum cleaners, and microwaves (the analysis would be different in business or industry where machines are used more consistently) , keep them till they keel over.
For more energy intensive appliances, like refrigerators, stand alone freezers, clothes dryers, hot water heaters and air conditioners, assuming you make regular use of them and that they’re not turned off six months a year such as in a summer home, it may be worthwhile to follow the EPA spokesperson’s advice and consider replacing those that are over 15 years old.
Energy scientists, especially, please weigh in on this post. I’d love to hear your thoughts. Meanwhile, tomorrow’s post will be not about the science of appliances, but about the approach we’re taking in the formerly No Impact household.
Photo courtesy of the New York Times.