I'm new to hot tubs since my brother in-law gave me his since he and his wife stopped using it. They bought it used and it is in great shape.
My question is how much clearance should I allow from the rear of the spa to a wall for one of those spa cover lifts.

There are tons of lifters out there. Can you give us the Spa model, year, and what brand and model lifter you are looking at?

Not sure of the year but it is a Sweetwater and the model is a Harford. I'm just looking for an average clearance that should cover most cover lifts.
I was just looking at Covermate lifts on an online store and theirs call for a clearance of 8" to 18"+ depending on which model cover lift. So I guess that kind of answers my own question.

Covermate is a good product - we use them. They are aluminum. I don't think they use stainless screws but they do include plastic caps for the screws.

Thanks for the reply Peteyboy...I would be surprised if Covermate did not use stainless screws on their products. I know around my above ground pool every screw is stainless and I always use stainless when replacing any hardware. Looks better and you don't have to worry about taking something apart due to rust.

That's a good idea. Covermates use a lot of screws.
Goo Luck