If the heat is non-electric and the water is gas, you probably are still OK to use a 200 amp service with a sub. A better way would be to install a 300 or 400 amp service, giving you either 2 -150 amp panels or 2- 200 amp panels. But that starts running the cost up. Is this a bid job or will the owner/builder listen to why this would be better? I've always found with homeowners that they want the ability to expand and if you tell them that they'll be maxed out with 200, they'll go for the 400.
