Air Conditioning - Central air conditioner/Heater

I have central AC/heater. What exactly I need to do in terms of yearly maintainence?

For AC people use 1 ton or 2 ton terminology. I am familiar with KWH. What exactly is 1 ton or 2 ton unit. Tons means how big the motor or size of AC or how much energy it uses? what are the conversion units tons to KWH?

How one would determine what capacity unit is needed?

Clean air filter inside check and see that inside AC coil is clean blower wheel is clean. On some motors there is a oil plug that you can oil the motor. Outside power off use just hose to wash out condenser coil. Can check fan there if it has oil plugs.

On AC 1 ton is 12000 Btu a 2 ton is 24000Btu .A ton is like what is the out put of the AC not in just how big the motor is .
Now the KWH is the electric power you will us on a AC unit.The higher the SEER of the unit the less KWH that you will use.
How one would determine what capacity unit is needed? You have to run a heat load on the home to see what size AC you need

ED ;)

KWH = Btu,s / 3.413

5 kwh = 17065 / 3.413