The Chainlink

I've been close to installing my window units several times now, but then we cool off and things are reasonably bearable again with windows and a box fan.  Looks like we're supposed to get back down into the 70s in a few days . . .

Who all's getting by without AC, and who plans to do so through the summer?

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Power consumption is a factor of the size of the units and how often they run.

How often they need to run is somewhat a function of size -but more so the heat differential between the outside and the inside being cooled, the degree  of insulation and air-tightness, relative humidities, and radiant heat getting into the area through windows.

Someone like me has very little cooling load living in  sunken garden unit in contact with the cool earth, with decent insulation, a neighboring living space right above us that uses AC too (cold sinks you know) and good shade to the windows with multiple insulating cellular blinds and plantation shutters which makes them very efficient.  Another person living in a sunny location with poor insulation and lots of blacktop around the building sucking up and spreading the suns heat all around will need to spend a lot more money to cool.  

Another thing:  It's better to under-size an AC unit(s) and have it(them) run more than over-sized and have it(them) run less.   The former will be more efficient than the latter provided it can keep up with the demand.   And finally central AC will beat out window units every time if it is sized correctly. 



h' said:

I had my two window units in last year-- newish 5000 BTU Frigidaires with thermostats-- kept them on something like 78 degrees and still had $120 electric bills. My place is under 800 sf.


Then I guess my heat differential is much much worse than Sol's, all other factors sounding about the same.

I personally don't like air conditioning. As long as the windows are open, I'm good!

been trying to get an AC unit from Wood Dale back into the city for over a week now.  ive already built a ground level bed because it was too hot in the loft bed.  i can handle the heat during the day, but need it cold at night!

I think when using window units, the key for affordable electric bills is to have units which are appropriately sized for the space to be cooled. An undersized unit will have to run constantly to keep up.

There is always the debate about whether you use more energy overall if you only use the ac when home versus leaving it on all the time...since I changed how I operate from last year, I guess I will be able to answer that question when my next electric bill arrives.

Well, as long as there's an AC thread-- I have a couple of tenants, clean-cut young cyclists, who need a working window AC unit and have no budget whatsoever . . . just got a text that the crappy ones they had seem to have failed; if anyone can help I'm sure they can pick up.

It's at worst break even if you turn it off the air conditioner or heat (during winter) when you're not at home and may quite possibly be much more advantageous to turn it off.  The basic idea is if there's a difference in temperature between the the inside and outside of your place, you'll get a heat flux of f(ΔT) where ΔT is the temperature differential between the interior and exterior temperature and the flux is watts.  Your heater or air conditioner will have use at least W_2=f(ΔT)*t amount of work in order to keep your place at a constant temperature where t is the time that the air conditioner or heater would be off.  If your heater or air conditioner is off, then when you get back it will need to do a certain amount of work (say W_1) in order  get your place back to your preferred temperature.  However, the important bit is that the work (W_1) that must be done, is at most equal to the energy required to cool or heat the interior temperature to your desired temperature.  On the other hand, the work needed to  keep your place at a constant temperature  W_2 (=f(ΔT)*t) is not limited and increases as t increases so the longer you're not at home, the more energy your climate control system uses.  If t is longer than the time required for the interior and exterior temperature to equalize, then leaving the ac or heat on is wasting energy.  Also, the greater ΔT is (i.e. the greater the difference between the exterior and interior temperature), the shorter the time period before you start wasting energy.

 

A simple analogy is to think about a bucket with full of water that has a few holes in it.  If you need a bucket full of water some time in the future, it makes more sense to let the bucket drain and then fill it when you need it rather than to keep refilling the bucket as the water drains if it's going to be a long time before your need the water.  Here the holes in the bucket represent the heat flux through your home's insulation and the water is the energy required to keep your home at your preferred temperature. 



Sol said:

I think when using window units, the key for affordable electric bills is to have units which are appropriately sized for the space to be cooled. An undersized unit will have to run constantly to keep up.

There is always the debate about whether you use more energy overall if you only use the ac when home versus leaving it on all the time...since I changed how I operate from last year, I guess I will be able to answer that question when my next electric bill arrives.

So we are all talking apples/apples here in energy usage what kind of numbers are people seeing on their bills?

We have a little over 1000ft2 and I just looked at last month's electric usage and it is 464kwh.  My wife thinks this is wholly too much and we need to get an energy assessment to see where we are wasting it.  My thought is the electric drier is probably one of the biggest wasters as we tend to do a lot of laundry here -followed by too many computers/laptops plugged in and running all the time.  We watch very little tv but we have a DVR plugged in and going and a Wii idling on standby that has not been used in months.  That stuff can all be unplugged and save the parasitic loads.  I need to put a power strip into the TV entertainment center so we can shut the stuff down that we don't use very often.

It's not just AC that wastes power.  

With lights, every fixture in the house either is a fluorescent or a CFL upgrade -and I try to keep them off as much as possible anyhow.

When I lived alone -and didn't have a computer or laptop that was always running (or laundry in my unit) I used to have electric bills in the mid/high 200's as far as kwh's.    What do other people get?  I was reading somewhere that the average US household electric usage was in excess of 1000kwh/month.  That sounds crazy to me. 

Haven't hit the intolerable heat threshold, yet.  With a pair of Galaxy whole house fans, pulling 3560 CFM it's still okay.  When the outside temps surpass 100, the window AC's get called off the bench.

 

I just logged on to ComEd to see what my usage has been. It looks like in the non-summer months (heck, even last month) our usage floats between 130- 160 kwh. Amazingly, we only used 26 kwh in October. I'm not even sure how that happened.

 

Our biggest spike comes in July and August - 476 and 519 kwh

 

So yeah, more than 1000 seems really, really excessive unless you run a disco or own a pool/hot tub. Or maybe there are people that own REALLY large homes. But, I would think that's the exception, not the rule.


 
James BlackHeron said:

So we are all talking apples/apples here in energy usage what kind of numbers are people seeing on their bills?

We have a little over 1000ft2 and I just looked at last month's electric usage and it is 464kwh.  My wife thinks this is wholly too much and we need to get an energy assessment to see where we are wasting it.  My thought is the electric drier is probably one of the biggest wasters as we tend to do a lot of laundry here -followed by too many computers/laptops plugged in and running all the time.  We watch very little tv but we have a DVR plugged in and going and a Wii idling on standby that has not been used in months.  That stuff can all be unplugged and save the parasitic loads.  I need to put a power strip into the TV entertainment center so we can shut the stuff down that we don't use very often.

It's not just AC that wastes power.  

With lights, every fixture in the house either is a fluorescent or a CFL upgrade -and I try to keep them off as much as possible anyhow.

When I lived alone -and didn't have a computer or laptop that was always running (or laundry in my unit) I used to have electric bills in the mid/high 200's as far as kwh's.    What do other people get?  I was reading somewhere that the average US household electric usage was in excess of 1000kwh/month.  That sounds crazy to me. 

You sir, are my hero!

I need to try some stuff to get our electricity usage down.    Are you using a gas or electric clothes dryer?  Ours is electric and I fear that is one of our largest electric hogs.  We can't do gas because of the lack of venting. 



Jim S said:

I just logged on to ComEd to see what my usage has been. It looks like in the non-summer months (heck, even last month) our usage floats between 130- 160 kwh. Amazingly, we only used 26 kwh in October. I'm not even sure how that happened.

 

Our biggest spike comes in July and August - 476 and 519 kwh

 

We definitely have an electric dryer. I'm not sure how many loads you run, but I'd say we do laundry about once a week, to the tune of three or so full loads (towels, sheets, clothing.)

 

My wife is really, really good with unplugging EVERYTHING not needed for use during the day. That means that our alarm clock, laptops, lamps, window A/C units and even our microwave is not using ANY electricity during the day.

 

We don't have pets or any other living creatures (that I willingly know of) in our apartment by day, so it's not bothersome to let the place get toasty.

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