3-tons sounds like alot for 1300 square feet. 3.5 for that size is crazy.

I think 2.5 tons at most would be good. Even 2.0 tons if your well insulated.

I thought long island didn't get to hot. Does it get humid there? how much is your electric per KW in long island?

Do you have a lot of big windows facing the sun?

It does get humid here, I'm on the south shore in a waterfront community. No big windows facing the sun. The house is over 50 years old.

I tend to favor Trane, which might be a bit more expensive, but Rheem is very popular here in FL too. How many returns are you getting installed?

1300-sf in Long Island, or Central Park, NYC NY; summer design around 89-dry bulb 73-wet bulb or around 46% RH.

With high rates of air infiltration that level of humidity translates into a high indoor latent load at, say an indoor 75-F temp.

Therefore, do everything you can to reduce air infiltration & then do a manual D & I'd select lower on A/C tonnage.
Possibly a 1.5-Ton condenser with a 2-Ton cooling coil with a TXV metering device. (We cannot tell enough from here!)

Not liable for what you end up doing.

The decision is yours; but know what the sensible & latent heatloads are before you make any other decisions. udarrell

Here is a link that might be useful: Sizing New Equipment & Duct System

3.5 tons sounds way oversized for 1300sf. I have 3 tons for 1750 sq. feet and it does fine. Long cycles remove lots of humidity, are better for the equipment and more efficient.

I would think 2.5 tons is plenty. If your pretty well insulated and good windows I would consider 2 tons.

3.5 is absolutely too big. I live in NC and have huge windows with no shade yet and I am very cold at 750 sqft per ton.

A little caulk and 2 tons should be fine. But you should get a man J.