Well, my 5,000 BTU(1.5kW cooling) air conditioner struggled to maintain
75°F when it was 100°F outside. The compressor ran continuously and it
simply will not pull down a small room below 75°F and it took a long
time to get down to 75°F.
My portable space heater which is also 5,000BTU/1.5kW can maintain 72°F
just fine when it's 30°F outside and it doesn't have to run continuously.
How come my A/C struggles to maintain 25°F difference running
continuously whereas my heater can maintain 40°F+ difference without
running continuously even though they both have the same BTU performance?
Both results were with the central HVAC turned off.
No, but you are failing to consider the heat gain that normally takes
place winter and summer.
Winter or summer you have lights (all add heat as well as light), water
heater, adds heat inside you home, windows generally create a net gain of
heat both summer and winter, almost all electrical devices from the door
bell to your computer add heat all year, even you add heat when you are
home. During the day in both winter and summer, the outside of you home
(roof and walls) are heated during the day and that increases heat gain.
Now add to the fact that your A/C not only cools the air, but dehumidifies
it and you can see why it takes more BTUs to keep you home cool in summer as
it takes your heater to keep it warm during the winter, with equal temp
Generally a good install will call for a closer match of A/C size than
heat because the A/C will dehumidify less well if over sized.
You have only once source of heat removal (cooling) with the AC, but you
have many heat sources helping the space heater.
The AC is pulling down the air temperature and heat is still getting into
the room from various sources. The walls not only tot he outside, but to
the rest of the house are transmitting heat into the room. The crack under
the door. Lights, TV, even your body. IIRC, an average adult gives off 400
Btu per hour just sitting in a chair.
The heater is getting help from all of these sources. Daylight hours it is
getting solar heat. While the outside temperature is 30 degrees, what about
the rest of the house? Are all the walls at 30 or are they closer to maybe
60 giving a lesser differential and thus lesser heat loss?
While 5,000 Btu is still 5,000 Btu, the heating and cooling loads are not
necessarily equal in the particular room.
Only sorta slightly related, but Im running a water source heat pump,
cooling house and heating swimming pool concurrently......
Water flow rate is ~7 gpm, incoming water is at 84 deg F, outgoing at 96 deg
F--so I'm figuring it's moving roughly 40,320 btu of heat--this is a 3-1/2
Anyone care to double check my numbers or have any questions / comments ???
Good grief, there are certainly a lot of "logic"
answers here, most with some but not much merit.
Simply stated, it takes a LOT more energy to drop the
temp a degree than to raise the temp a degree, because
of the methodologies. The technology for increasing
temperature is simply much more efficient that that for
lowering the temperature.
If you have a mass and remove 5,000 Btu or add 5,000 Btu, it is still the
same amount of energy it is still the same mass. Since Btu is really an
expression of Btu PER HOUR, the same amount of energy is being moved in the
same time period.
Take the window AC unit and mount it backwards so it exhausts from the
condensing coil the heat into the room. Would the effect of running it
raise the temperature more or less than a heater that gives of 5,000 Btu of
heat? If two rooms were the same temperature and one had the heater, the
other h ad the AC (assuming the outside air is at the temperature used to
get the 5k rating), which room would be heated more?
True, but the LOSSES (efficiency) of causing that are
grossly different. Your analogy is sound, but it ignores
the losses involved in makng that change occur, which is
what the OP was asking about. I'm afraid getting into a
technical debate, especially one with the lossless descrip
you're trying to use would be futile and take way too much
ether and time. Keep reading; it's there.
So, Newton was wrong?
The technology for increasing
This is the biggest non-sense posted in my thread.
Space heater can only output as much heat as the electricity going in
and this will not change. Simple law of conservation of mass.
Cooling is more efficient. You can take about three units of heat from
inside and take it outside with one unit of electricity. The condenser
will spit out three units taken from inside + one unit used by the
What does Newton have to do with this? Possibly you're confusing the three
laws of thermodynamics, with Newton's three laws of motion.
Not at all -- he's absolutely right. You need to go back to school.
Heating is more efficient than cooling for two reasons: First, *all*
mechanical processes eventually dissipate *all* their energy as heat. Thus the
energy input into a heating device is all converted to heat. So is the energy
input into a *cooling* device.
Second, the laws of thermodynamics work in favor of heating, and against
cooling. The temperature gradient is downhill for a heating system, and uphill
for a cooling system. Simply put, a heating system transfers heat from a warm
object (e.g. a furnace) to a cool object (e.g. a room); this transfer occurs
spontaneously. A cooling system, OTOH, transfers heat from a warm object (a
room) to a *hot* object (the outdoors -- obviously it's hotter outside than
inside, otherwise why are you running your air conditioner?). This transfer
does *not* occur spontaneously, and requires additional energy to force the
heat transfer uphill.
Actually, that's "conservation of *energy*".
Speaking of nonsense... you just won the prize. Cooling is *far* less
efficient than heating.
So you're saying that air conditioners operate at an efficiency of 300% ?
Sorry, I don't buy that.
There isn't any such thing as "cooling energy" anyway. "Cool" is the absence
of heat. An air conditioner does not create "cool". It moves heat from inside
the house to outside the house. This is an uphill temperature gradient, and is
guaranteed to be a less efficient process than heating a home, which moves
heat on a downhill temperature gradient from a warm furnace to a cool room.
Then suggest you look at the nameplate ratings then--and note that while the
heater draws ~ 1500w, while the A/C likely only draws ~ 500w
I run heat pumps here year round.......when the outdoor temps drop below 40
deg F, heat pumps drop off in effeciency, and so the backup electric heat
strips kick in--when this happens, my electric bill also about
500W at 240V = about 2 amps. That's not much of an air conditioner. Even at
120V, it's only about 4 amps, not even a decent window air conditioner.
Better check those nameplate ratings yourself; I think you're missing
something. Maybe you're looking at the rating for the blower, instead of the
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