This is the code for the calculator I made for Brian Grimmett's Westar story.
There are two formulas we are using, provided by Westar.
The traditional formula is: ((First 900 kWh * rate for the first 900kWh) + remaining kWh * rate for remaining) + service fee + (rider * all kWh))
This volume rate changes base on Summer and Winter months.
The new formula is: (all kWH * volume charge) + service fee + (rider * all kWh) + (demand * demand rate)
The demand rate changes based on Summer and Winter months.
I first wrote the code in a ipython notebook since I'm more comfortable in Python.
I then used jscalc.io to make the calculator.
The code used in that calculator is in calculator.js.