How To Calculate Percentage Rate Increase With Annual Summary

What I need is a worksheet which will generate fields from a set of variables (similar to a loan amortization schedule).

I don't know how to write the field code to include the annual percentage rate increase based on that additional input variable.

Input variables would be:

starting rate: (ex: 8¢/kilowatt hour)
starting date: (ex: July 2013)
average kw hours/month: (ex: 1062.5 kw hours)
annual rate increase: (ex: 3% *default 0%)
years to display: (ex: 25 years, *shown in months in fields below)
service months per year: (ex: 12 *default 12)

[code].....

So, data fields below the variables would be blank until these are entered.

Assume I would protect the sheet to avoid messing it up.

this would generate a chart showing rates over time from the fields below.

Also it would generate fields in a summary area to show the rate per year for future years.

Secondary, if there were a way to input actual usage and rates from specific months in the past, that would be useful but not part of this forecast model.

The goal of this model is to forecast electrical costs for residential power users compared to independent solar power generation to 25 years forward.

I want to make this because I am skeptical of the advertised savings that solar installers use to convince clients that their return on investment is so high. I believe their data to be greatly inflated projections.

Using this in comparison with other data such as inflation and wages will allow me to get a very good economic picture of the future of independent solar energy generation and its impact on the average home owner.