you have to figure out how much electricity your A/C system uses.
Look at the data plate and see Wattage....or kilo Wattage ..that's what is used when its running. Watts is volts x amps. The A/C's in my condo unit are 240 volts on a 40 amp circuit, so they use just less than 9,000 watts when running.
How many hours a day does the A/C run? Lets say its on 20 minutes and hour over the course of 24 hours; 8 hours times 9,000 watts is it burns 72,000 watts a day, or 72 kWh. So now you know how much electricity you need a day.
Also, at, say 20 cents a kWh charged by your power company you're spending $15.00 a day for the A/C. If your local power bill is lower, adjust the numbers below.
A solar system is inefficient in the mornings and the afternoon when the sun hits the panels at an angle......the DoE has a 'solar calculator' for where you live showing how many usable hours a day you get. For the Caribbean its 6; assume where you live its 4,
A Kyocera 175 watt panel costs $700.00. AT 4 hours a day it makes 700 Watts of power. You need a battery bank to sore the energy for cloudy and overnight use, an inverter to take the panel energy down to 14 volts and another to take it back up to 140 v to run the A/C.
Looking at the example above, I would need 10 2 foot by 3 foot panels to maybe make enough to run the A/C. That's $7,000 in panels, another $3,000 in batteries and inverters and installation. Call it Ten Grand.
At $15.00 a day saved paying the electric company you'd get a payback in 2 years if you ran the A/C every day. If you only ran it in summer, say 100 days a year, you'd break even in 6 to 8 years.
If your power bill is ten cents akWh, then its 4 years and 12 to 16 years.
See why people don't have solar panels?
just put in a 70,000 dollar system.