HOMER can model deferrable electrical loads like water pumping or ice making.  For details, please look up 'deferrable load' in the index of the help system.

HOMER can also model an electric boiler, although in a simplistic way, since it does not model its cost and it assumes the electric boiler has an infinite capacity to convert electricity to heat.  To model an electric boiler, click the Add/Remove button, add a thermal load to the system, and then open the System Control Inputs window and check the checkbox near that bottom that says 'Allow excess electricity to serve thermal load'.