Most central air conditioners run off of 220/240 V AC to drive a refrigerant through a heat exchanger and to operate a fan. These large units are used to cool entire homes up to 2200 ft2. On the other hand, room air conditioners run off of 110 V, usually cool up to 300 ft2 and can be easily powered from power generated from solar panels. Depending on the climate in which you live, the savings in power can easily pay for themselves in a few years.
Typical room air conditioners use about 1200 Watts but newer models are becoming much more energy efficient and consume around 600 Watts. Before powering the unit from solar power, find a unit that balances low power consumption with good air-conditioning comfort. The lower the power consumption, the lower the number of solar panels you'll require.
Once you've found a comfortable room air conditioner that uses as little power as necessary, determine the number of solar panels you require. [See: How many solar panels to make one kilowatt?] The solar panels will be generating direct current (DC) which will then be inverted to alternating current (AC). If you only need the unit to be running during daylight hours, then this system will probably be enough for you.
A charge controller is necessary to maximize the output power of the solar panels. Look for a unit with a current rating that is high enough to accommodate the total output current from all of the panels put together. A maximum power point tracking (MPPT) circuit is necessary to optimize the energy efficiency of the array.
Since air conditioners run off of AC, an inverter is necessary to convert the DC power to AC power. Look for a unit that is rated to handle the power load of the air conditioner. Most come with a three-hole socket which can accept the 110V power plug from the unit.
If you need the air conditioner to run well into the night, you'll need additional energy to be stored in batteries (you can also learn about the possibility of reconditioning and using old deep cycle batteries here). Adding extra solar panels to the array will generated enough energy during the day to run both the air conditioner and to recharge a battery bank. Revise the number of solar panels required by taking into count the extra power needed to run the unit for an extra 4-8 hours after sunset. Make sure you have enough room in your yard or on the roof to accommodate the array of solar panels. [See: Retrofitting Solar Power]
Running your air conditioner from clean, non-polluting power will not only keep you cool but will also help reduce the chances of having rotating summer power outages. A solar power air conditioner will have its own dedicated power supply that will provide comfortable cool air even when the main power is out.