I have a 100 amp service in a small house with 4 open spaces in the electrical box. Need to run a compressor to put on a new roof, for the guns. What size wire and breaker should I use. I will run one solo wire from the electrical panel 25 feet to the plug. I have a 20 Position electrical panel box.square d

Do you already have the compressor? If not you could get or rent a gas powered one and that would do the job that your looking for. That way no electricity at all is involved.

If you do already have one then do you know what it is rated at? Is it 110 or 220 ? If your in the U.S.

220

Look at the rating plate on the compressor. It should show you voltage and amperage. Find that out and get back, we can't guess at the amperage.

To size a motor circuit, need to know the horsepower and voltage rating listed on the nameplate of the motor.