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For anyone who spends a little time in Texas heat, you find quite quickly that air conditioning is a very serious topic here. So messing about with a home’s working AC equipment as I have done is, generally speaking, looked upon as crazy. There’s talk of interrupting circulation and “overworking” things, plus every other type of armchair quarterbacking imaginable. However, I did it anyway and wound up with some interesting results.

My home is one story and a touch over 2,000 square feet. In the summer months it’s not difficult to keep cool, but it is expensive — almost triple what the spring/winter months cost, to be exact. So AC is the real trick.

While watching the Travel Channel visit exotic places I will never go, I spied an idea. In an exclusive Italian town I saw a villa equipped with a smart AC system to cool only the bedrooms the residents were sleeping in during the night instead of the whole house. That gave me an idea.

I only use two bedrooms in my house at night. I can’t afford the uber-smart central air with its temp sensors and computer controlled flow; this was a fact. But why couldn’t I mount two window units in those rooms and set the central air for the entire house to 78 or 80 at night, then use much smaller, say 6,500 and 5,000 BTU units to make up the difference in those bedrooms? As it turns out, I can.

The larger of the two units was a Frigidaire LRA074AT7 window unit with a 6,500 BTU capacity. It has all the modern bells and whistles like auto mode, which makes it run just like your normal central air system by sensing room temperature, and of course a remote. I also picked up a smaller 5,000 BTU unit from the same manufacturer that had all the same features except for the remote. They ran $150 and $99 respectively. Each was rated for the room size of the spaces they were set to cool and installed in a window of that room with the door closed during the night.

So armed with last months electric bill and the bill from the previous year in the month I was going to test, I carried out the plan. It turns out when all bills were totaled up, April this year cost me $176 and May was $129. So it was already less than the cooler month before it. Looking at last year’s May bill suggested more savings at $211 vs. the new $129. So anywhere from $50 to $80 a month in early summer months. A good start.

Is this a sure thing? No, of course not. However, should this continue to work going against last year’s numbers I will have at least broken even by August, and that’s worth something right there. More data and further unscientific testing needs to be done on my part. Plus figuring up kilowatt/Hours per unit, hours run and the like would help as well.

That said, this little experiment does assist with several areas that I can already see helping in the long term. The first is it saves wear and tear on the large central AC unit that is on less during the night. The other is that we now have backups in case the central unit does go out completely, which can be very ugly down here where triple digits are commonplace.

More on this experiment as developments occur.

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34 Responses to The Texas A/C Experiment

  1. Lars H says:

    Pros: A good night’s sleep, reduced electric bill, smaller carbon footprint.

    Cons: Window-mounted AC units poking out of your bedroom windows.

  2. Sean O'Hara says:

    @ Lars H this is true sir. And I’m lucky that all my bedrooms are in the back of the house where no one cares and doesn’t have to look at them.

  3. hmbemis says:

    I had an idea like that too, a lot of people said that I was crazy, I’d mess things up, etc, etc… but I did it anyway and found that it worked just as well.

    My idea was drinking water out of a coffee mug instead of a cup, what I found was that it worked just as well, and now I save wear and tear on my cups which is a bonus.

    I also have a backup in case my cup breaks.

    …just kidding, but this seems like a painfully obvious idea, and I find it funny that it took watching the Travel Channel for you to think of this? LOL.

    So not only do we do this up here in New England already (I used window a/c’s to supplement the central air in our last rental house both to save money and to help spot cool rooms in the finished attic which had a/c vents/returns but was still much hotter)…

    We also will run an electric heater in our bedroom at night… I keep the house at 62* but keep the bedroom at 68*… even though it’s electric, it’s still cheaper to run it vs. the central heat.

  4. Sean OHara says:

    @hmbemis yep, apparently we are that behind the curve down here. Not sure why it’s not done and frowned upon.

  5. Tom says:

    Wow, AC in April? We have had a hot spring in MI, but I have only run the AC on day. Usually I turn it on for about 5 days a year. Our power company offers interruptable service for a central AC unit (on a separate meter) at a discounted rate. They have only had to interrupt service once in 5 years.

  6. Rick says:

    I live up near Denton, TX. I simply don’t run the AC at night. I just have my ceiling fan running.

    Of course I was raised in Louisiana where it is not only hot but very humid. I grew up in an old house with no central air, we just had an attic fan. My wife is from Japan, where central AC is very uncommon. She is just as used to heat and humidity as me.

    I do run the AC during the day. I work from home so it is running all day. I installed solar screens on the windows and installed a solar powered attic fan to help cool it down. The net result is that my electric bill has never gone over $200 in a month (despite rising Texas electric cost from deregulation). Also, I’m have the only house in the neighborhood that still has its original AC unit (built in 2000). It’s the cheap system that was put in when the house was built but I simply don’t put as much wear and tear on it.

  7. I grew up in Northern NY State and never had AC in our 1840′s-built house or, for that matter, in either of my parent’s vehicles. There would be a week in August or so every year where we desperately wished we had it, but even the hot days (90s F) would drop down to the 60s at night.

    I’ve lived in Texas now for 12 years, and have come to see AC here as pretty much the equivalent of heat up north. The biggest surprise for me living here is that the nights don’t cool down much at all, and take until 5 or 6 am to drop to the low point. It’s not unusual here to have a 98-degree day stay in the 90s until midnight, then never dip much below 80 overnight. So keeping the house at a sleepable temperature, even with fans assisting, can get pretty expensive.

    Why is it that so few down here use AC window units? I’m not sure. But Sean is correct; AC in any form besides central air is fairly uncommon in our suburban environment. Maybe it would be like living in North Dakota and having one or two small space heaters in your house during the winter (i.e., extreme suffering for all but the heartiest of crazy coots). Then again, I remember growing up we had an oil heat system that blew through floor vents, a wood stove, a pellet-burning stove, and several smaller portable heaters. Why that system doesn’t transfer to AC plus portable units, I’m not sure. I suspect it has to do with the economy or the age of homes (up North homes are much older than most down here).

  8. Daniel says:

    I’ve used the same strategy in S. Louisiana for several years now. There’s an added benefit in areas prone to occasional extended power outages, in that the window unit can be run by a small generator for the duration.

    On a related note, check out homeclimatecontrol.com which is a DIY zoning & control system for your existing central AC. I’ve wanted to put one of these systems together for years, but can never find the time.

  9. jonathan peterson says:

    mini split ACs are not a lot more expensive than window units and are a heck of a lot more elegant. A buddy of mine put one in his kitchen to keep it comfortable while cooking without messing with the rest of the house.

  10. Senorpablo says:

    When you hear the hippies and liberals on TV talking about energy conservation, this is exactly the sort of thing they’re talking about. Not only on an individual level, but industrial and commercial as well.

    Your results are impressive. Imagine if everyone in your city did this, then the state, then the country? People save money, and we free up fuel/energy resources and become less dependent on oil producing countries. If the air-conditioners you purchased were made in the US, or at least sold by a US company, so much the better for the economy.

    Incandescent light bulbs are being phased out here in California in favor of more energy efficient technologies. It will be interesting to see if it has the desired impact and if other states follow suit. The smallish city I live in, pays about $90,000 per year in electricity for street lights, and they’re moving to more efficient lighting. In only a few years, the cost of all new lighting fixtures and labor for installation pays for itself in energy cost savings. Innovative companies like Honeywell have programs to fund the up-front costs to replace equipment, and they take payments from the energy savings only spread over many years. They sell more lights, the city saves money–it’s win win for all. This is exactly the sort of forward thinking we need here in the US, not the stubborn: “they way we’ve always done it is good enough.”

  11. Drew says:

    Jonathan is right. Get a split unit. We use them overseas all the time (because houses are made from brick/concrete without duct work). You individually set temperatures in room and turn them off in other rooms. Plus they are not ugly.

  12. stagepin says:

    @Senorpablo – Lennox just came out with an AC/HP that will accept solar panels. We sell them here in the DC area and we figure that with 8 solar panels (that backfeed into the house power) you can generate 117% of the electric power needed to run your AC over the year.

    The only problem is that it’s a $20k investment that pays for itself in about 10 years. It’s a long term solution and a lot of people just can’t realize the cost up front.

  13. Sean O'Hara says:

    Hmmm, that may indeed be more elegant but both the units I have total less than half of the split units I’m seeing. I’m all for graceful looking stuff but not sure prices starting around 600- 1000 for the same kind of BTU coverage I’m looking at really justify them for me yet.

  14. ambush says:

    Not many people know this but window air conditioners are more efficient in terms of btu’s per watt as well due to stricter EPA standards.

  15. zoomzoomjeff says:

    @ambush. Actually, I didn’t know that. We had a window unit in our upstairs bedroom in a cape cod style house last summer to help. I haven’t planned on using it again because of the looks, and thinking that it used a lot more energy. I’ll have to re-evaluate things and calculate what I think is most efficient. Either way, summertime generally sucks for electric bills!

  16. Dar says:

    I have found that making sure that the attic is convection cooled properly is actually cheaper than any AC unit. Cool air in at the eaves, hot out at the peak. Dropped the cooling bill by 50% and the temp by 20degF in one rental house I was in.
    Also, when in shade, the window AC units do not work as hard or use as much energy. Make a shade or shadow over them with plywood or equal.

  17. ambush says:

    I mean don’t get me wrong, the difference in minimum efficiency between a central unit and a window unit is probably only 5% or so, and if the window unit is really old standards may have changed or it may have lost some refrigerant. If the compressor is cycling really frequently that’s a sign that it is low on refrigerant. Oh and Dar is right about the shade thing, makes a fairly big difference.

  18. ecrusch says:

    Whatever works.
    And if you keep saving, the units will be paid for in no time.
    Thanks Sean.
    Eric

  19. Mitch says:

    I’m in Milwaukee, WI, obviously not a comparison with TX. It does get somewhat hot here though in the summer. I can usually get by with a whole house fan that will cool the entire house at night. This only works if it gets cool at night of course.

    During the day, I then close up all the windows and shades to contain the cool. I have to run the central AC only about a week when we get temps above 90 for that week.

  20. IronHerder says:

    If I repeat earlier points, it is for emphasis, because this time I really did read the entire post (nicely written, BTW) and all of the useful comments (and the other comments, too: just kidding, the iceberg principle–90% of everything is BS–doesn’t seem to apply to TM).
    I am still surprised that Sean wasn’t subject to a restrictive covenant that prohibits window units. But regardless, congratulations on your monthly savings. Does it go for your tool budget?
    And I hope the TM staff continues to post on subjects that some readers may consider “painfully obvious”. Because we’re not all Lloyd Bridges, who said, as Admiral Benson, “Do I have to think of everything?”
    The only downside for me is that I am forcefully reminded that I need to get my attic vented and I need to add insulation to my attic. Meaning that my beloved shop upgrade is that much delayed.

  21. MR P says:

    Another way to save money is to plug your AC or Apace heater into a programmable thermostat for the good old fashion AC with the numbers 1-9 to set the temperature will with this piece you can control time and temp 4 times a day.

    I put one on my ac and it stayed off 80% of the time turning it completely off. And you don’t have to remember to go turn on and off the ac in the kids bedroom. Just set it and forget it.

    http://luxproducts.com/thermostats/win100.php

    Available at Amazon and Lowes

  22. Deelow says:

    To get the most accurate information you would have to have a months worth of your electricity bill running the central air turned down to the same temperature every night and then compare it against a bill of one month using the window units at the same temperature every night. That seems like the only way to get the most accurate information.

    Neat expirement thought. Can’t wait to see more test results.

  23. Barks says:

    We use Fujitsu mini-splits in individual rooms (offices, changing rooms, etc.) in the barns , with a Seer rating of something approaching 23.

  24. Mac says:

    Great post, and comments.

    My .02:

    Ceiling fans in d@mn near every room in the house help tremendously. Fan on when in room, off when not in room. AC cut back several degrees = big savings.

    Upgrading the windows are pretty costly, but will pay you back eventually. Summer shades/awnings for the windows also help.

    Others are spot-n with the attic cooling too.

    Lastly, programable themostat. (or adjust manually if you can work it out.)

    Cheers.

  25. Paul says:

    I design commercial MEP systems for a living. A point that needs to be made is that a good design in the beginning is key. It s just like the cheap tools tht are argued for or against on here, a quality tool may cost more buy will do the job more reliably over time.

    Customer A indicates he needs to replace his broken central AC and he needs to keep on a tight budget. The installer may or may not really design a system for his home, it may just be oh, well 2000 sqft translates to a 2-ton unit, your existing vents are there and since you are on a budget we’ll re-use them as is…

    Customer B wants to replace his system and wants the best all around system so he will spend less year round but may be in a little deeper in the beginning. insulation will be added, vents will be sized properly for the load of each room, depending on the location where you live the unit will be sized accordingly. In the midwest you will get a system designed for 92 degree summer day. In texas maybe the design temp is 102. This means your system should be able to keep up until you surpass that temp.

    As far as a window unit goes, its a great way to supplement a poorly designed system for little money. You don’t need to be an engineer to choose a window unit that will serve a room well, everything is in the box and sized properly. Just block off the vents in that room and it will take a little load off the central AC system.

    My home has this same issue, my house is 80 years old, the insulation could be better, there are rooms all the way to the roof (no attic) so those rooms don’t have the benefit of extra insulation and venting an attic could have given me. My duct-work was added for central AC and it was sized to fit the area where the installer stuck it and not sized to fit the room. That’s how it was when I bought the house. So my window AC units certainly help on 90+ degree days when we have near 100% humidity here.

    Another thing that may work well in humid area are dehumidifiers. It is easier for your central air system to cool dry air than wet air, so dehumidifying will remove the water and make the central AC use less energy cooling excess liquid in the air.

  26. Brant H says:

    Awesome idea! I didn’t see any mention of connections between the central house system and the window units. There’s nothing tying all three together, right?

  27. Josh says:

    i have a small 900 sq ft apart, it has a 15.000 btu in the wall ac–i got 2 lil 5000 btu window units(hayer wallmart 89 bucks each) 1 for main room and 1 for bedroom -the 15k btu is a 220 power-vs the 2 small are 110–i save about 25 bucks a month to cool usin the 2 small ones been usin them 3 yrs now -plus alot quieter.i live in the Philadelphia area

    • captainhurt says:

      is a “small 900 ft apart” smaller than a “large 900 ft aprt”? :-P
      dont let the mortgaged mansions con you into a “new (larger) normal”. houses are downsizing these days.

  28. electronbee says:

    Another thing to look into, if you have windows that get sun, is tinting them. HD sells window tint with different reflective values. When I was in VA Beach almost all my windows got the afternoon and setting sun. This resulted in the whole place heating up. The window tint paid for itself in one month and dropped the electric bill considerably. I got the highest value which made the place a little dark sometimes but TX is more south and brighter.

    Another thing one can get is a portable AC unit. It’s like a window unit, but, its on wheels and has a duct for the outside. I tried using that idea for a bit but the model I had had a lower SER rating and it was cheaper to use our central AC since it had been recently replaced and had a much higher SER rating.

  29. Frosty says:

    AC in April is nothing. We’ve been unseasonably cool the past two years, but for the three years before that, AC was getting kicked on by March permanently and sporadically through the winter when the sun baked the house too much. The California desert was not meant to be inhabited in my opinion.

    Our summer electricity bills are $400-$600 depending on how much time when spent travelling. We have friends with $800-$900 bills, but they have bigger homes (1400 sq. ft. vs. ~2500). We pay 40 cents/kWh…not sure what the norm is.

    We’re moving to a new place and doing this same thing…supplementing central AC with window units to improve cooling and save money. I don’t see it used around here at all, but I’ve been doing it for about fifteen years now. I think it is common sense for those of us who grew up in areas without central AC (northwest, northeast, Europe) being standard. We are used to window units so when we go somewhere even with central AC, our first thought is “window unit” when the central AC can’t keep up with the sun’s rays.

    The main problems with this solution are (1) window coverings and (2) installation.

    Installation is incredibly easy in windows that open up and down, but a big pita for the, more common in newer homes, side-opening style. I always have to basically build a new frame with 2x4s for the unit, block the top or bottom open area with plywood, insulate, and paint. The window can then no longer be locked so I have to seal it shut.

    Then, because the AC unit sticks out into the room slightly (unless you have deep casements), we have to buy new window blinds to fit the new shorter width.

  30. NikuSama says:

    Very interesting i was thinking of something similar soon.

    I’m moving into my parents old house since they have up and left for bettr jobs and one of the rooms is plagued with high temps and the master is quite big, its even a similar sized (2100 sq/ft) single story house but in southern oregon where temps still hit tripple digits but humidity plays a factor as well.

    the plus side the more moisture in the air the better the window ac units will work and theres a 5K btu one at sears open box for $60.

    so one will go in the computer room and the other in the master, do what you do at night but block off the vent in the computer room and only have the small 5k BTU on when i am in there, plus some sun shades are in order….gonna red neck some of those up some how

  31. Jeff Wright says:

    IF you are only concerned with cooling for sleeping purposes, look into wha tis calkled the “Bed fan” it is incredible. It is a fan that attaches to the foot board of your bed and blows cool air UNDER the top sheet, unlike a ceiling fan that blows on top of the blanket never touching your skin, this fan blows directly on you and it takes very little to keep you cool all night. I absilutely love mine!

  32. Rick R. says:

    Sean,

    Great post.. Glad you’re keeping cool in this weather. I’m not sure how feasible it is for you, or desirable for that matter, but most of the window AC units can also be installed in the wall. When we moved into our apartment, there were two AC window units that the previous tenant had left behind, and so I talked my dad into letting me take them out of the windows and put them in the wall (we were replacing the old wood double hung windows with new vinyl replacements). That worked out so well for the two bedrooms on the south side of the house, that we bought two more units, one for the north east living room, and one for the North west master bedroom that normally gets hammered by the setting sun (2nd floor). The only rooms without an AC unit are the bathroom (East facing), the kitchen (North facing with the LR and a BR on either side) and the hallway connecting everything (L-shaped).
    Those four units have been running this year pretty much non-stop since late April. My electric bill has been right around $215-230 per month. Generally try to turn them up during the day when no one is home, and up at night. Although when I and/or the wife weren’t working for a bit, they were running 24/7. Not the cheapest, but they are all mounted in the wall, the windows are all free and clear. Two units face north, and the ones that are facing east and west respectively are tucked up high on the wall just under the roof eaves to help with some shade in the mid-day sun at least.

    We love it. Effectively gives us central air for the whole apartment, with three backup units just in case one fails. The house is in dire need of some new insulation, but for us that is more of a problem in the winter than in summer. During the summer we also take precautions like using insulated curtains in the kids’ rooms (the two south rooms) which have the added benefit of completely blocking all of the light.. so the kids sleep longer (that’s the hope). We keep those closed as much as possible in when we don’t need the light. The ceiling fan in the living room also helps keep air circulating, as does the one in the kitchen. I tend to run the stove’s range hood fan almost all of the time on low. I think (perhaps misguidedly) that this will suck some of the colder air from the rooms with the AC units into the kitchen.. while the ceiling fan there helps keep it moving as well.

    Ok, enough of my diatribe.. Good show Sean!.. good show!

  33. Rhonda says:

    Me and my husband bought an 1960′s ranch style home in Jan 2010. We never went into the attic to look at things until last year, noticed alot on squirl poo(old), crawled around and noticed there were holes in the duct, taped it up. Just had the A/C guy come out last week due to the Central A/C not working good, have the thermo set on 65 and in the afternoon with temps outside running 105-110 only cooling our house to 88 inside. Hot!!! We were quoted $1100 to get new duct installed, really, who can afford thea, we opted to doing it ourselves. Cost about $300 to replace all the ductwork up in the attic. Got that done Saturday, noticed a change in the living area, but the back bedrooms were still blazing from 5-7 pm CST. Opted to get a new window unit and plan on getting 2 or 3 more. Was told that the average Central AC in texas if it is running really good will only drop the temp in your house by 20-30 degrees max with Texas heat. So I think we are just going to opt for the window units!!! My Electric bill 2 months ago was 179, last month 250, and this month 354. I can’t handle the increase. I think it will be well worth the investment. FYI everyone around her is having the same idea, AC window units are in short supply.

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