Nobody else has said it, but the lead length between the TVSS and your panel buss bar is critical. Most recommend 6" or less...this is harder than it seems to arrange in your typical residential panel.
The best setup is a unit that goes between your meter and your socket. However, most EUSERC utilities won't allow this. Second best is a unit that sits directly on the bus bars of your panel. Depending what you are dealing with, they make ones that look like breakers and pop on, all the way up to factory built in units that bolt next to the main lugs. Third best is an external unit that sits next to your panel. I have used ones from Leviton that have plug in surge modules, allowing for quick and easy replacement. They are also fused to prevent a n extended short. The way I usually hook these up is to order a meter main with a 200A breaker, and a 50A breaker, and run the 50A to the TVSS, and the 200A to a subpanel.
