Power Inverter For Air Conditioner Article
accommodate the large energy demand.
AC Load
Air conditioners up to about 12,000 BTUs can be run successfully on an inverter. These units require approximately 12 amps AC (1.4kw) when they are running. At start up however, they need up to 5 times as much power for a few seconds to get going. This requires an inverter that
has a high surge rating as well as a fairly robust continuous rating. The Freedom 25 for example has a continuous rating of 2,500 watts and a surge rating about three times that. It can start and run most air conditioners of this size, but a large amount a DC power is required to generate this much AC power.
DC Load
As a rule of thumb, in a 12-volt system it takes 11 amps of DC power to generate 1 amp of AC power. If the process of energy conversion were 100% efficient, the ratio would still be about 10 to 1. Since 12 volts is being stepped up by a factor of 10 to 120 volts, the current ratio is also 10 to 1. But the inverter is about 90% efficient, so that is why the 11 to 1 ratio is used as a guideline.
This means that an air conditioner that draws 12-amps AC from the inverter is causing a 132-amp load on the DC system (12 amps x 11). At this rate, batteries are not going to last very long. For this reason, it is recommended that air conditioners running on inverter power only be used while underway, and a fairly powerful DC generation and storage system needs be provided. When it comes time to stop the engine, its time to shut down the air conditioner, or switch the air conditioner over to another source of AC power i.e.: shorepower or generator.
As a rule of thumb, in a 12-volt system it takes 11 amps of DC power to generate 1 amp of AC power. If the process of energy conversion were 100% efficient, the ratio would still be about 10 to 1. Since 12 volts is being stepped up by a factor of 10 to 120 volts, the current ratio is also 10 to 1. But the inverter is about 90% efficient, so that is why the 11 to 1 ratio is used as a guideline.
This means that an air conditioner that draws 12-amps AC from the inverter is causing a 132-amp load on the DC system (12 amps x 11). At this rate, batteries are not going to last very long. For this reason, it is recommended that air conditioners running on inverter power only be used while underway, and a fairly powerful DC generation and storage system needs be provided. When it comes time to stop the engine, its time to shut down the air conditioner, or switch the air conditioner over to another source of AC power i.e.: shorepower or generator.
