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I've decided to make public my ROI/Quote comparison tool that I created during my 2+ year analysis of solar panel systems. What I am providing is tailored for CA specifically. Most of the figures have been changed since I was playing around with my calculations to verify they are correct. You can adjust as you need for your own situation.
With this spreadsheet you can compare:
Break-even year
Cumulative cash flow
Cumulative utility savings
10 yr IRR
25 yr IRR
Est % Utility Coverage
You can adjust rate increases by year if you want. With my utility, SCE, there are some known increases coming in the next few years, and after that, reverting back to historical averages would give a pretty good picture of how your annual cost will go up.
In case you're curious about my process, I had additional sheets in there for my own use that had much more in depth pricing, usage, generation analysis for my specific situation. One sheet allowed me to view my monthly billing and I could see where increases and decreases in usage occurred. I got a better understanding of my actual usage patterns during the year. I even did solar hours calculations w/ degradation for each month and up to ten years dependent on tilt angle. From that, calculated approximate annual production. This was to compare with the CSI-EPBB calculator that the state provided to see if my calculations were close to theirs. More or less just an exercise allowing me to understand more about how all the numbers are calculated. Even did analysis on expected monthly utility bill based on power generation (summer vs winter months). This was to see if the "average monthly bill" figure provided by the contractors calculations jived with my own.
All this is a bit too much depth to get an understanding of the financial feasibility of the quotes that you receive from various contractors. It also becomes too complex when you start dealing with 5+ quotes, so I've left them out. I only did those more in depth analysis on one quote to verify my findings with their calculations. Suffice to say that their calculations were slightly more optimistic than mine.
Let me know if you see any errors. I hope there aren't any.
Hope this helps some of you in your research and analysis.
Shared as a google doc. Download and edit highlighted cells as needed.
With this spreadsheet you can compare:
Break-even year
Cumulative cash flow
Cumulative utility savings
10 yr IRR
25 yr IRR
Est % Utility Coverage
You can adjust rate increases by year if you want. With my utility, SCE, there are some known increases coming in the next few years, and after that, reverting back to historical averages would give a pretty good picture of how your annual cost will go up.
In case you're curious about my process, I had additional sheets in there for my own use that had much more in depth pricing, usage, generation analysis for my specific situation. One sheet allowed me to view my monthly billing and I could see where increases and decreases in usage occurred. I got a better understanding of my actual usage patterns during the year. I even did solar hours calculations w/ degradation for each month and up to ten years dependent on tilt angle. From that, calculated approximate annual production. This was to compare with the CSI-EPBB calculator that the state provided to see if my calculations were close to theirs. More or less just an exercise allowing me to understand more about how all the numbers are calculated. Even did analysis on expected monthly utility bill based on power generation (summer vs winter months). This was to see if the "average monthly bill" figure provided by the contractors calculations jived with my own.
All this is a bit too much depth to get an understanding of the financial feasibility of the quotes that you receive from various contractors. It also becomes too complex when you start dealing with 5+ quotes, so I've left them out. I only did those more in depth analysis on one quote to verify my findings with their calculations. Suffice to say that their calculations were slightly more optimistic than mine.
Let me know if you see any errors. I hope there aren't any.
Hope this helps some of you in your research and analysis.Shared as a google doc. Download and edit highlighted cells as needed.
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