Want to get a tankless water heater that requires a 300 amp service, and 3 60 amp 2 pole circuits. I have 2 large 200 amp panels in a 5000 sq/ft house built in 1995. Am I fairly safe to assume that if it was built to code, that the service is at least 300 amp? Wouldn't the county, power company (or whoever had to inspect and approve it) know? I really don't want to have to pay just to find out. Is there an easy way to tell? Couldn't really see an "Amp" rating on the meter or the transformer box outside, or on the big metal box located below the circuit breaker panels that has the inspection labels and plastic tamper seal things on it.

Also, when I went and looked at the meter, I was surprised to see that the conduit going into it is only 1 inch in diameter, now, I always thought that all the electricity going to the house has to go through that meter. Seems to me that 1" is a little small to be servicing 2 200 amp panels! Am I right? Or just making assumptions based on a lack of knowledge?

Any help or reassurance would be appreciated!

Thanks

You really should have an electrician survey your service, and do a service rating calculation to see exactly what you have for connected load, service rating and what is needed to add the new water heater.

What you have told us is no help in determining the total size service you currently have. Perhaps photos may help.

We certainly cannot do a load calculation, and therefore cannot tell you if the existing service can handle the additional load.

A 5000 sq/ft home will be adequately served by a 320/400A service (which is what you have), BUT, add a HOG of an appliance like the beast you are proposing and even that may not be enough.

No way I'd try and use a whole house electric water heater in a McMansion like this.

Who is selling you on getting one?