There are two types of electricity, alternating current (AC), which changes direction periodically, and direct current (DC), in which the current only flows in one direction. In the late 1800s, there was a public feud between Thomas Edison and Nikola Tesla (for whom the automobile company is named) over which type of power is better. Edison was a proponent of DC power whereas Tesla favored AC power. It turns out, depending upon the application, they were both right.
The power that we get from the electric company is AC current, because it is easier to transmit over long distances with less loss of power. Most of the large appliances in your home such as refrigerators, stoves, dishwashers, and washing machines run on AC. However, electronic devices such as computers, flat screen TVs, cell phones, and batteries all run on DC. Depending on the make and model, electric cars run on either AC or DC current, but the batteries that supply the energy are all DC. It is relatively easy to convert AC current to DC current using a rectifier. For example, when you charge your smart phone, a rectifier in the charging block converts the current to DC, which is used by your cell phone.
Most central air conditioning systems run on AC. However, many of the more advanced and efficient air conditioning systems on the market today use inverter technology. An inverter system converts the AC current into DC. With an AC system, the compressor is either on or off, causing the unit to repeatedly start and stop to maintain the desired room temperature. Compressors which run on DC power are smaller, quieter, and can be modulated up or down to run at different speeds, like a dimmer switch on a light fixture.
With all central air conditioning, it’s important to match the size of the equipment to the required cooling load. Obviously, on a 90 degree day, the demand for cooling will be significantly higher than on a 70 degree day. Because DC inverter technology allows the compressor to ramp up and down, the system modulates to match the cooling output to the cooling load. This causes the unit to cycle less frequently, remove more humidity, save energy, improve comfort, and extend equipment life.
If you’re in the market to install or replace an air conditioning system, you may want to consider one like the Bosch IDS (pictured), which uses inverter technology.