Home Electrical Savings?

[MrCritical]

My home is about 2100sq/ft heated. We have a 4 year old heat pump/whatever. It is pretty efficient. Children are raised and gone, wife and I work all day.

This months electric bill (total electric)was $113. At bedtime, it's just us and we close the door to our bedroom. Set the electronic thermostat on 71 degrees.

We were wondering if it would be any savings to getting a small window unit to cool just our bedroom and turn the thermostat up to 80 or so for the rest of the house.

I wondered about the efficiency of these small units. Our central unit does not run that much to keep the whole house cool. I had questions about how much juice the small unit would use if the compressor turned on more often than the big unit.

 

[JHZR2]

Buy a good, high efficiency unit that is underrated. Freidrich makes good ones, IMO.

THe most efficient unit is generally one that is undersize and has to run most all of the time.

JMH

 

[tom slick]

having an undersized a/c unit is more efficient then an oversized unit because it cycles on and off less. When the unit is cycling on is when it uses the most power. an undersized unit also more comfortable because it mixes the air better by running the fan instead of dumping in a bunch of cold air then shutting off. that helps to remove more humidity too.

of course a properly sized unit is the best.

 

[pbm]

I'm thinking of having central a/c installed in the near future. The a/c season in NY is approx. May till Sept. Is anybody knowledgeable about brands, SEER etc.. and would like to share some advice?

 

[oilyriser]

I remember seeing a small window unit that had a timer so you could program it to start an hour before you get home, or an hour before you go to bed. The really small ones take less than 1000W.

Any way to cut the amount of solar heat getting inside?

 

[Al]

Window units are the only way to go. Why cool the whole house when you are only in one room? Its an idea who's time has come. The small difference in efficiency is a moot point, really. Our bedroom is 12 x 14 (pretty small). We have a 5000 BTU unit that keeps us comfortable in the hottest of nights. It takes about 4.5 amps.

We like to sleep in cool. We keep it at say 66F at night with no problem.

I wish they had window heat pumps (Not split system)

Get an undersized unit and let it run all of the time. Our addition (20 x 20/cathedral ceiling..3 exposed walls)has a 6800 BTU unit. It cools that room and the adjacent kitchen.

 

[Schmoe]

Get a programmable thermostat for your main HVAC system. You can preset the times you want it on instead of strictly relying on temperature. Worth its weight in gold. Remember, window units are pretty noisy, if you like quietness, don't bother. You also got to think in terms of thermodynamics. Once you get your house to a desired level, ALL things inside are at that level. If you want to cool the house down when you are home and before going to bed, your AC will have to run longer because you have to recool everything in the house, kind of like a heat sink. It is cheaper to maintain a temperature as opposed to trying to cool everything off again. Notice how your house probably stays cool inside in the morning, early afternoon hours as it gets hot outside? That's the result of having everything inside cooled off already. Don't think you'll save that much money maintaining a comfortable setting in the house versus a window unit in the bedroom and then having to crank up the AC for the times you are not in the bedroom. Also, check to see if your power company has average monthly billing. I pay about 70 bucks year round. That way I don't freak when the high bills come in the summer.

 

[blackcherry06]

My house was built in 1979 and this spring I replaced the original Carrier unit because it finally gave out. Well...honestly, the bottom of the compressor rusted out over the winter, so there's no telling how much longer it would have run if it weren't for corrosion. The last time we used it in the summer, it was pumping 35 degree air out the vent closest to the air handler...pretty good for a 29 year old unit I think.

Going on my experiences, I'd have to recommend Carrier. I had a 13 SEER unit installed (goverment requirement - 13 seer is a minimum) and it's working beautifully. $4900 for a complete unit w/heat pump. If you want more efficiency, I think they go up to 21 seer..or some number in the 20s and the outside units are HUGE. Depends on your budget.

Now I just have to get over my paranoia of copper thieves. I'll drop dead if my unit disappears.

 

[Al]

Originally Posted By: Schmoe
Don't think you'll save that much money maintaining a comfortable setting in the house versus a window unit in the bedroom and then having to crank up the AC for the times you are not in the bedroom.

That's so totally not true. Energy use is strictly based on the temperature difference between the inside of the house. Obviously it is based on the area of the walls, roof, floor,etc. And it is based on the time duration. Also bear in mind, many rooms will have less wall exposure ratios than the whole house. So there is even greater benefits. I cool my bedroom at night (even turning it on for 4 extra hours) at a cost of 10 KW...about $1.00. What does it cost you to keep your whole house cool at night so you can have one bedroom cool?

Also, it is economically better (generally) to keep the house warmer during the day when you are not there vs keeping it cool. Again it all revolves about inside/outside temps, time, and area of exposure. Naturally if you keep it warm and over cool the results may not be desirable. But consider the scenario where no one is in the house for two days. Does it pay to main a lower temp during that time? Probably not.

 

[MrCritical]

My Carrier is 4 years old. I have the cheapest electric bill of all my neighbors. It has 10 year warranty, but maybe they all do.

 

[Schmoe]

Al, I RESPECTFULLY disagree with you. If the house is well insulated, it should be able to withstand outside temperature variations with minimal notice. When the house gets warm, it's not just the air, it's everything that is inside the house, the walls, furniture, carpet, appliances, etc. etc. All those things have a cool demand also. That's why ceiling fans have become more popular over the years. It doesn't cool anything, but it makes you feel cooler by thermoevapotranspiration (sp??).
It just feels cooler. If you leave the AC off for that long, then you got to re-pay to cool everything back down so why waste that money? A good, well matched AC system in a insulated house will match the costs of a window unit any day. Please note that this is in terms of overall costs, not just one day or night.

 

[TooManyWheels]

Originally Posted By: Schmoe
... If you leave the AC off for that long, then you got to re-pay to cool everything back down so why waste that money? A good, well matched AC system in a insulated house will match the costs of a window unit any day. Please note that this is in terms of overall costs, not just one day or night.


Repay? You don't repay, you had two days of savings. An air conditioner is horribly inefficient, any time it runs it is leaking. So the less it runs, the less you are penalized. And it is the worst when it is just maintaining a temp, because it is constantly stopping and starting.

Ideally, you're house would have been cooled just once when it was built, then never again because you would still be using the original cool. But obviously the cool leaks out, and you are essentially cooling the outdoors every time you run your unit. I like to cool the outdoors as little as possible.

 

[oilyriser]

Ducted central air systems leak like crazy, and so can a window unit, but you can more easily fix the leakage in a window unit.

I have seem a window unit heat pump on the shelf of a hardware store in the US.

 

[brianl703]

There are also ductless mini split systems that have heatpump functionality.

 

[Al]

Originally Posted By: Schmoe
Al, I RESPECTFULLY disagree with you

That's O.K. I gave you the simplified Engineering facts. Ask another Mechanical Engineer the same question. You'll get the same answer as mine. I'm also an M.E. (not saying I'm special)

ToManyWheels has it about right. The cooling of the furniture/walls could waste money under certain conditions of ratios of that mass to the total load loss out of the walls/roof/ etc. It gets a little tricky. But its unlikely to occur.

And the fact still remains..its cheaper to cool one room than seven. That was my main message. Hard to dispute that one. You won't need to be an M.E. here.

 

[Al]

Originally Posted By: TooManyWheels


Repay? You don't repay, you had two days of savings.
Ideally, you're house would have been cooled just once when it was built, then never again because you would still be using the original cool. But obviously the cool leaks out, and you are essentially cooling the outdoors every time you run your unit. I like to cool the outdoors as little as possible.

Hahahah..this just struck me as funny.

 

[duaneb9729]

no most units dont have a ten year warranty, my company currently is a carrier dealer and in the past 31 years we have been a Rheem dealer Trane and Bryant and lennox dealer, all have there good points and all have some minor draw backs.

if you choose to go with a set back thermostat dont go wild with the amount of degrees difference between when your gone and when you are home. lux makes an ok set back thermostat and if you want one with a great easy to read screen look at the white-rodgers brand, thats the one i use in my own home

 

[TooManyWheels]

Originally Posted By: Al

Hahahah..this just struck me as funny.

Thank You, Al. I was trying to frame the situation in a way that would make people picture what was actually occurring

 

[Julian]

Isn't heat exchanged with the outside air to produce the cold air inside to begin with though?

 

[duaneb9729]

no julian, the refriderant is used for the heat transfer, under a low pressure it absorbs heat and under a high pressure it gives off heat, the indoor part of the system, in the cooling mode is under a low pressure which allows the refriderant to pick up heat from the house and dehumidify mostly because the temp of the indoor coil is lower than the due point of the entering air