How long do things last?
June 21, 2013 11:05 AM Subscribe
When should I replace a window-mount AC unit?
I have a window-mount AC unit that gets, at most, two months of use a year - the rest of the time, it sits in the garage. I believe as of this year it's 10 years old (or nine, but certainly no less than that). It still seems to work fine - as with anything mechanical of that age, it creaks and squeaks a little more than it did, but otherwise it still seems to cool the room just as well as it always has.
Is there a point, though, at which running this unit is less efficient than buying a newer model? I've always been of the "run it into the ground" school of thought about most things, but it occurs to me that it might be more ecologically/energy-bill/whatever-else efficient to replace an AC unit after (x) number of years rather than running it for (x + however many). I don't know what that number is, though.
I have a window-mount AC unit that gets, at most, two months of use a year - the rest of the time, it sits in the garage. I believe as of this year it's 10 years old (or nine, but certainly no less than that). It still seems to work fine - as with anything mechanical of that age, it creaks and squeaks a little more than it did, but otherwise it still seems to cool the room just as well as it always has.
Is there a point, though, at which running this unit is less efficient than buying a newer model? I've always been of the "run it into the ground" school of thought about most things, but it occurs to me that it might be more ecologically/energy-bill/whatever-else efficient to replace an AC unit after (x) number of years rather than running it for (x + however many). I don't know what that number is, though.
The coolant will eventually start to leak out and it will get less and less efficient.
However, I bought one at a garage sale in the early 2000s. It was definitely from the 90s. My parents used it after me up until a year or two ago and it was still VERY strong when being 15+ years old.
If the air that comes out is still "Ice cube canon" and not just "maybe sorta cold" then keep using it. New ones might draw a few less watts, but technologically ACs have been pretty flat for a while unless you spring for one of the super high efficiency ones which are really overpriced anyways.
posted by emptythought at 12:31 PM on June 21, 2013
However, I bought one at a garage sale in the early 2000s. It was definitely from the 90s. My parents used it after me up until a year or two ago and it was still VERY strong when being 15+ years old.
If the air that comes out is still "Ice cube canon" and not just "maybe sorta cold" then keep using it. New ones might draw a few less watts, but technologically ACs have been pretty flat for a while unless you spring for one of the super high efficiency ones which are really overpriced anyways.
posted by emptythought at 12:31 PM on June 21, 2013
We just had to deal with this question at my house, so I'll share my logic.
We had been given (second-hand) 2 ancient very large very heavy AC units (fake wood paneling, can't even be carried by one person). One did a great job of cooling our somewhat large living room, and then one June we plugged it in and nothing happened. That was the end of it. Bam, gone, got a modern unit. The other did a good job the first year, a barely-adequate job the second year, and the third year we moved it to a smaller room where it was fine. This was a big unit, and it just wasn't quite handling the amount of cooling I would've expected a big unit to do. Is it burning as much power attempting to cool as it used to when it really cooled? I don't know. We then had to choose whether to replace it with another big unit that would do the living/dining room space, or to continue limping along. What we decided to do was to buy a small unit for the living room, and keep the big one in the dining room (used less frequently) until it dies for real, at which point we'll replace it with another small unit. Our summers are very short - we need AC during about 4 weeks spread over about 3 months of summer, so it would take a huge difference in efficiency to add up to much savings at all over so little time.
(days used per year)*(number of hours per day)*(power used by your AC in kilowatts)*(electric cost per kwh) = cost to run an air conditioner for one year
A modern 8000 BTU unit uses about 6Amps (720 Watts) when it's running but over the course of a 24-hour day it will be cycling on and off. Let's say it's actively running for 10 hours per day (that's a huge overestimate, in my opinion) for 60 days of the summer (also probably an overestimate). 10h/d*60d*0.72kW = 432 kWh. Call it $0.12 per kWh (an average USA cost), give you $52 that you're spending on electricity. That matches with products like this, a $200, 8000-BTU AC that is estimated to cost $65 per year to run.
Say your old AC is half as efficient - this is highly unlikely! useful 1link refers to data saying that EER (efficiency) was ~5 in 1970, ~7.5 in 1990, and ~10 in 2012, so to get something half as efficient you'd be talking about a 1970's model, and a 2003 AC would be 90% of current efficiency by extrapolation. But imagine it's half as efficient, you'd spend $100 per year, or save $50 with a new AC, and in 4 years, you'll have paid off the $200 that the new AC is likely to cost you. That sounds reasonable, but still if you wanted to postpone it for a year, it wouldn't be the end of the world.
When your old AC was bought, it was 90% as efficient as modern ones, so you'd only be saving $7 per year, or the cost of a new AC in 25 years. Not reasonable. I guess the question is, has it aged to the point that it's operating much less efficiently than it used to? And is it doing anything else that annoys you? (not cold enough, cycling funny, noisy fan, too heavy, wish you had a remote control, etc) You can replace your AC, but it's probably not about efficiency.
posted by aimedwander at 1:30 PM on June 21, 2013
We had been given (second-hand) 2 ancient very large very heavy AC units (fake wood paneling, can't even be carried by one person). One did a great job of cooling our somewhat large living room, and then one June we plugged it in and nothing happened. That was the end of it. Bam, gone, got a modern unit. The other did a good job the first year, a barely-adequate job the second year, and the third year we moved it to a smaller room where it was fine. This was a big unit, and it just wasn't quite handling the amount of cooling I would've expected a big unit to do. Is it burning as much power attempting to cool as it used to when it really cooled? I don't know. We then had to choose whether to replace it with another big unit that would do the living/dining room space, or to continue limping along. What we decided to do was to buy a small unit for the living room, and keep the big one in the dining room (used less frequently) until it dies for real, at which point we'll replace it with another small unit. Our summers are very short - we need AC during about 4 weeks spread over about 3 months of summer, so it would take a huge difference in efficiency to add up to much savings at all over so little time.
(days used per year)*(number of hours per day)*(power used by your AC in kilowatts)*(electric cost per kwh) = cost to run an air conditioner for one year
A modern 8000 BTU unit uses about 6Amps (720 Watts) when it's running but over the course of a 24-hour day it will be cycling on and off. Let's say it's actively running for 10 hours per day (that's a huge overestimate, in my opinion) for 60 days of the summer (also probably an overestimate). 10h/d*60d*0.72kW = 432 kWh. Call it $0.12 per kWh (an average USA cost), give you $52 that you're spending on electricity. That matches with products like this, a $200, 8000-BTU AC that is estimated to cost $65 per year to run.
Say your old AC is half as efficient - this is highly unlikely! useful 1link refers to data saying that EER (efficiency) was ~5 in 1970, ~7.5 in 1990, and ~10 in 2012, so to get something half as efficient you'd be talking about a 1970's model, and a 2003 AC would be 90% of current efficiency by extrapolation. But imagine it's half as efficient, you'd spend $100 per year, or save $50 with a new AC, and in 4 years, you'll have paid off the $200 that the new AC is likely to cost you. That sounds reasonable, but still if you wanted to postpone it for a year, it wouldn't be the end of the world.
When your old AC was bought, it was 90% as efficient as modern ones, so you'd only be saving $7 per year, or the cost of a new AC in 25 years. Not reasonable. I guess the question is, has it aged to the point that it's operating much less efficiently than it used to? And is it doing anything else that annoys you? (not cold enough, cycling funny, noisy fan, too heavy, wish you had a remote control, etc) You can replace your AC, but it's probably not about efficiency.
posted by aimedwander at 1:30 PM on June 21, 2013
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Substitute 'AC Unit' for 'Car'.
If it still works, keep using it. If anything, it may have been built to a higher quality than current models as it's more profitable to build in a failure point so you'll keep buying 'new'.
posted by matty at 11:20 AM on June 21, 2013