As boring and redundant as it may sound, the very first step should always be to determine the actual load, as accurately as possible. The load should include the heat as well as domestic hot water (DHW), if the boiler or heat source supplies both.
The electric is typically one of the last things you do on an installation but you can’t treat it like a political conversation over Thanksgiving dinner. It can’t be avoided. Here are some tips for giving your clients professional-looking wiring.