I have a 200 amp panelboard. With the addition of my new workshop, I need to add about 90 additional amps of continuous power for my tools. Can I add panelboard to handle the extra power?

Since the existing 200 amp panel is sized to handle the home, adding 90 amps of continuous load will require that you upgrade the existing 200 amp service entracne to 400 amps. This will require new larger service entracne conductors , conduit, and meter. At the meter you can have two 200 amp distribution breakers, one to feed the existing panelbaord, and another to feed a new 200 amp panel for the workshop.

This can be quite a project, and concrens many variables depending on your situation.

Best to call in a contractor to design the layout and estimate the cost.