Sgreany-
I would use the 200A number.Thats what my local POCO does in their "green book" that we use to size the conductors.can the POCO bring in conductors overhead and set a pole closer?That would help some.Can the place get away with a 150A service? Either way the cost is going to be alot,I don't think there is anyway getting away from that,whether you use 200A or 150A as your load.If you go with 150Amps as the load a 350 MCM copper will have a VD of 3.67% according to my calcs.I would find out if the homeowner has thought of living "off the grid" and doing a solar/battery/generator set up(I know some folks who do it this way)price with the underground.
More importantly.
I would fiqure out a price on these numbers and see if the customer is serious or not about spending the big $$$ to get this service in.Otherwise your spending a bunch of days "banging your head" over this estimate just to have the customer say "I was only planning on spending X amount of dollars" or something along those lines.Don't forget to include a conduit(s) for phone / cable .Best of luck in getting the job.(I'm not available to pull 800 + ft. of wire with you Sorry. LOL) Andy
