I have a small studio - around 650 sq feet. I try to ask about energy
economy using my central air. There are two conflicting theories

1 Theory that most people follow : keep the ac all the time - when you
leave, just increase the temperature
2. Theory that I follow : when I leave I switch it off completely

Please tell me who is right ?
Explanation for my (#2) theory : I understand that the central unit
runs at the steady pace (?). It does not matter whether it is 95
degrees or 80 degrees in apartment ...once I set the temp to 75 degrees
(when I come back from work) the ac will be blowing air at the same
speed, consuming energy at the same rate. True it will take it longer
to knock down temp from 95 to 75 (40 minutes ) than from 85 to required
75 (20 minutes). But ..assuming that you leave the apartment and set
the tempt to 85 the ac will switch on/off multiple times during the
9-10 hrs period you are away from home which will in effect be longer
(more energy consumed) than 40 minutes. Please provide me with some
good information - am I rite on this ?

The reasoning might get qualified if

A) somebody had large, good insulated house and it would take him
horribly long to knock down temp from 95 to 75. So I guess in this case
it be better to just allow ac unit to switch off/on for short periods
of time during 9-10 hrs you are away from home.

B) The ac unit runs at different speeds ..consuming more energy with
higher spread between present temp in the apartment and requested temp.

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oups.com...


I have a small studio - around 650 sq feet. I try to ask about energy
economy using my central air. There are two conflicting theories

1 Theory that most people follow : keep the ac all the time - when you
leave, just increase the temperature
2. Theory that I follow : when I leave I switch it off completely

Please tell me who is right ?
Explanation for my (#2) theory : I understand that the central unit
runs at the steady pace (?). It does not matter whether it is 95
degrees or 80 degrees in apartment ...once I set the temp to 75 degrees
(when I come back from work) the ac will be blowing air at the same
speed, consuming energy at the same rate. True it will take it longer
to knock down temp from 95 to 75 (40 minutes ) than from 85 to required
75 (20 minutes). But ..assuming that you leave the apartment and set
the tempt to 85 the ac will switch on/off multiple times during the
9-10 hrs period you are away from home which will in effect be longer
(more energy consumed) than 40 minutes. Please provide me with some
good information - am I rite on this ?

The reasoning might get qualified if

A) somebody had large, good insulated house and it would take him
horribly long to knock down temp from 95 to 75. So I guess in this case
it be better to just allow ac unit to switch off/on for short periods
of time during 9-10 hrs you are away from home.

B) The ac unit runs at different speeds ..consuming more energy with
higher spread between present temp in the apartment and requested temp.

You aren't just cooling the air. If the several tons of building material
that make up your flat get warm to the touch, they will radiate that heat
back into the room.

aem sends...

Essentially by turning the AC off for periods when you are away you are
doing the same thing as those that just turn up the thermostat. Just
view it as turning the thermostat up so high that the AC never comes
on.

IMO, the best practice is to turn it up as high as possible, or off,
and have it resume at the appropriate time so that the house will be
comfortable when you return. The amount of heat coming into the house
is directly proportional to the temp difference. So, the bigger the
temp diff between inside and out, the more energy required.

The only possible advantage to the idea of not turning it off or
setting it way high when not around would be if the system can cool the
house easier at those times. For example, if it's 70 outside, the
system is going to use less energy than when it's 90 to produce the
same amount of cooling. So, it could be argued that during times when
it's coool, you could be maintaining the house for less energy than it
will take later, when it will be 90 and now you have to bring the house
back down. However, I doubt this makes up for the energy that will be
constantly lost will maintaining the house at the lower temp for long
periods while you are away.