Air Conditioner wattage consumption
- Thread starter KasseemF
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gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
110909-0837 EDT
An air conditioner is basically a servo system. Averaged over some time period it requires a certain amount of energy to do its task. This averaged energy requirement will depend on the heat flow rate into the area being conditioned, the desired temperature in that area, and the temperature of the area to which the heat is pumped.
Thus, if any of these factors change the average energy required per unit of time will vary.
So the easiest way to calculate the kWh required for some reasonable time period, like a day, is to measure the actual kWh input to the actual machine under the temperature conditions of interest. From this you can calculate an average power.
My freezer power vs time curve is sufficient to give you an idea of what an air conditioner might do. The times, power level, and exact shape would be different, but the general characteristic would be the same. See P29 at http://beta-a2.com/EE-photos.html .
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An air conditioner is basically a servo system. Averaged over some time period it requires a certain amount of energy to do its task. This averaged energy requirement will depend on the heat flow rate into the area being conditioned, the desired temperature in that area, and the temperature of the area to which the heat is pumped.
Thus, if any of these factors change the average energy required per unit of time will vary.
So the easiest way to calculate the kWh required for some reasonable time period, like a day, is to measure the actual kWh input to the actual machine under the temperature conditions of interest. From this you can calculate an average power.
My freezer power vs time curve is sufficient to give you an idea of what an air conditioner might do. The times, power level, and exact shape would be different, but the general characteristic would be the same. See P29 at http://beta-a2.com/EE-photos.html .
.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
What's your goal here? Consumption would be energy and therefore implies kWh, power is kW alone. Using current can only be used to calculate kVA which does not really tell you power or energy consumption, you will not know the power factor (or time). If all you have is a BTU rating, that is a peak value so all you can get from that is peak kW as well, which is useful for determining current for circuit loading etc. If you are after energy consumption, ie kWh, then you can estimate a high value by assuming peak BTUs continuously for the running time (BTUh) and converting to kWh, or to be accurate buy a low cost energy meter like the Kill-a-Watt and just measure it.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
110909-0959 EDT
I believe your have two major problems. Inrush or startup peak current (peak power), and what happens when the sun intensity is too low to operate even the steady state load. You are not concerned with kWh.
On startup you are limited by the inverter capability and its short time internal energy storage (capacitors). This is a peak current and duration problem. Any motor at startup time requires a current many times (like maybe 7 times) its steady state current.
If your system has batteries to allow 24,7 operation, then you may have the peak power capability if the inverter is large enough.
A small generator (meaning size relative to load) has the same problems.
If you had a soft start motor system, then the conditions would be somewhat different.
.
I believe your have two major problems. Inrush or startup peak current (peak power), and what happens when the sun intensity is too low to operate even the steady state load. You are not concerned with kWh.
On startup you are limited by the inverter capability and its short time internal energy storage (capacitors). This is a peak current and duration problem. Any motor at startup time requires a current many times (like maybe 7 times) its steady state current.
If your system has batteries to allow 24,7 operation, then you may have the peak power capability if the inverter is large enough.
A small generator (meaning size relative to load) has the same problems.
If you had a soft start motor system, then the conditions would be somewhat different.
.
Last edited:
K8MHZ
Senior Member
- Occupation
- Electrician
Yep, same as with a water pump, the in rush current required won't be available with just solar panels sized to run the motor.
There are a couple choices. One is a stand alone system with lots of batteries. The other is a grid tied system that provides the extra power needed for in rush.
If you have big bucks, a hybrid system with an anti-islander and an ATS is the way to go. But, if you had that kind of money, I don't think a few bucks extra on the electric bill to run the A/C would be that much of a concern. The big advantage would be uninterrupted power.
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