Consider improvements to Electricity Purchases input page

[cpaulgilman]

SAM's Electricity Rates page was originally designed for behind-the-meter (BTM) financial models to calculate bill savings = bill without system - bill with system.

As of SAM 2017.9.5, we added electricity rates to the front-of-meter (FOM) financial battery configurations to better account for the cost of charging batteries. This proved to be useful for accounting for PV inverter night-time consumption, and for CSP parasitic losses as well. Now, electricity rates were being used to calculate an operating cost instead of bill savings.

For SAM 2020.11.29 r2, we changed the label for FOM configurations from "Electricity Rates" to "Electricity Purchases" to make it clearer that the retail electricity prices are to calculate the cost of purchasing electricity.

For SAM 2024.12.12, we added Single Owner and Commercial financial model options to the industrical process heat (IPH) configurations that generate heat and consume some electricity.

This issue is to review the implementation of the "Electricty Purchases" input page in the user interface to see if it can be streamlined to make it easier to add to future configurations for both BTM And FOM applications, taking into consideration the need to remain consistent with the Utility Rate Database (URDB) API.