So I finally have central air conditioning and I’m trying to figure out how to use it. The last month has seen a lot of days in the 85-95 degree range, so it’s been very hot.
I thought it would be efficient when leaving the house to turn the thermostat up to 85 or so and then when I got home turn it down to 75 or so. What I found was that it would take all night for the house to cool down, so sleeping was uncomfortable, but by the morning, it would be freezing.
Thoughts?
Get a programmable thermostat. Then you can have it automatically adjust the temps. For example you can have the AC cool the house better about a half hour before you normally get home. You can have it kick on even cooler around the time you go to bed.
I pay market rates for electricity which isn’t all that common for most homes. What that means is my kilowatt costs are usually much, much cheaper (about 2.5¢ kwh) after midnight compared to around 5 to 13¢ kwh during the day. It behooves me to crank down the AC at night so that I sleep good plus cool the interior of the house. BTW: I also do things like run the dishwasher and do laundry late at night are very early in the morning.
My experience is also that it simply takes too long to cool the house down if you turn the central air conditioner off when you leave and turn it on when you come home. My guess is room air conditioners tend to be oversized for what they are because people expect to be able to turn them on and cool the room down rapidly, while they do not expect that of a central air conditioner.
My personal preference is that 75 is a bit on the cool side, my own is set at 77. If you have a programmable thermostat and a regular schedule you might set it to start cooling an hour or two before you come home.
hope this isn’t too obvious, but add more insulation. in the house I used to own I had to put in a ton to get my mortgage and I ended up being glad because it took forever for the house to warm up on a hot day.
also, plan shade trees - it makes a big difference.
and - as long as I’m spending your money - how about a whole house fan to take advantage of when it’s cool at night.
You are doing the right thing by letting it get hotter in the day, but as JerrySTL said, sounds like you need a programmable thermostat. Get it to turn on an hour before you come home.
You mention it being freezing when you get up. Don’t turn it down colder than you want it to get. Turning the temperature down lower does not make your AC cool the house down faster. It just runs longer until it gets to that temperature.
That would be awesome. Me want.
In Illinois it’s called Power Smart Pricing. Other States and even countries may have similar options. I remember that there as a scheme in England where electricity was cheaper for 7 hours a night. This was when I lived there around 1990. Things may have changed.
Poorly insulated house?
And/or improperly sized A/C? Your unit might be undersized. But you don’t want an oversized unit, either, if you don’t like humidity and mold.
I typically set the thermostat to 85 during the day and have it set to drop to 78 about an hour before I get home to give it a chance to cool. It doesn’t take more than that hour for the temperature to fall. And that’s in the Houston area, where hot and muggy is the norm most of the year.
Shade trees also help, but insulation is going to help the most.
My thoughts as well. The AC should be able to take the house down to the appropriate temp in a reasonable amount of time. Something else is going on, either a poor/inefficient/broken A/C unit or a very poorly insulated house.
85-95?? Try 95-108!
My suggestion is just leave it on 80 all the time, it’s a good tradeoff between not being too hot and not costing too much.
Gnerally speaking, it is cheaper to let the house get hot during the day and then cool it down when you get home. Similarly, in the winter it is cheaper to let the house get colder during the day when you’re not home.
The reason for this is that the greater the temperature differential between your house and the outside, the more heat transfers from one to the other (heat coming into your house in the summer or going out in the winter).
That said, the OP has run into one of many reasons why this may not be practical. A programmable thermostat can certainly help. Just program it to turn on the AC early enough that the house will be acceptably cool by the time you get home.
You can do the same thing in the winter using the programmable thermostat to control your furnace.
There are other problems you can run into though. If you are in a humid area (think Florida or Louisiana, for example) you can end up with a jungle’s worth of mold growing inside your house from the heat and humidity of letting the house get hotter during the summer (AC also functions as a dehumidifier). In the winter, if you let it get too cold, your pipes can freeze and burst. This can happen even if the temperature inside the house doesn’t get down to freezing. Pipes will often be in outside walls, and the space inside those walls will be closer to the outside temperature than the rooms in the interior of the house. Also, if you let the house get too cold and you have an efficient heat pump system, it can go into a less efficient, higher power mode if the temperature is too low, and the inefficiency from this may be much worse than the amount of energy you would have saved by reducing the temperature during the day. Some heating systems have settings to prevent this from happening.
There’s also the comfort factor. You may save money, but if the house isn’t cool enough for your liking then you’ll be miserable inside it until the AC manages to get it down to a reasonable temperature. It may be worth the extra money to you to keep the house at a constant temperature just for your own comfort. Many AC systems designed to be efficient can really struggle at extreme temperatures, so you can also end up with situations like the OP where it’s just so hot that the AC system can’t cool the house down in a reasonable amount of time. Having heating and cooling systems with a greater BTU capacity can overcome that, but they won’t be as efficient when they don’t have as much work to do. Everything is a tradeoff.
I purchased inverter units for all rooms in my house – from 32,000 BTUs to 12,000, I have four units – and although they are about 30/35% more expensive at purchase, in less than a year and a half I’ve already amortized their initial cost. My electric bill is now typically 40 to 45% less and I run my ACs a LOT more. Mind you, I live in the Tropics, where there is hardly a day that goes by that you don’t need to use them. Very happy with my decision…aided by a very trusted AC technician I’ve known for a long time. Fact is, they are slowly outselling regular split units.
A bit of additional info: Benefits of Inverter Air Conditioning
There is no way to tell the difference between 75 and 77 on my thermostat. I have a new one ready to install but I’m hesitating doing it myself because I don’t want to break anything.
As far as insulation goes – would installing new insulation in the attic be enough? I’m not in a position to tear out the walls to install insulation.
It couldn’t hurt (well, I guess it could hurt your wallet). But whether or not it would do a lot of good depends on if it’s actually a problem in the first place. Adding attic insulation worked a treat in the house I grew up in, which was built on the cheap, but YMMV.
Another thought that strikes me is thermostat placement. The thermostat itself may not be in the best location and may be partly responsible. This is a more unusual problem but if the central A/C was only just installed, it’s a possibility.
The AC was not recently installed in the house. I was.
What type of central A/C system do you have? If you have a heat pump, that could be your problem. In my experience a heat pump generally produces a fairly narrow range of temperature differential, so if you let the house get too hot it will take a LONG time to cool back off again. The only way we could maintain a comfortable temperature in the house we had with the heat pump was to set the thermostat where we wanted the temp to be and LEAVE IT THERE. Needless to say, when the heat pump finally cashed in its chips, we replaced it with a conventional unit.
How do I tell if it’s a heat pump? It looks like any other forced-air system I’ve seen.