I have a 5 ton central AC, I have a medium size Chest freezer, I have a medium size refrigerator. I have probably 300 watts worth of lights. How many watts will this be and what size emergency generator would I need for this?

Impossible to tell unless you can provide Amperage of the units. Watts = Amps X Volts. You can look on the model/serial # plates for amperage and then multiply X Voltage. AC will be 240 VAC, others at 120 VAC. You already have light wattage. Also need to consider that startup Amperage will be greater than running Amperage and therefore so will watts increase. Generator should have a max wattage and a running wattage rating.