My Interest costs ARE the running costs for the sytem for the 15 year warranty timeframe. That capital I "borrowed" is set aside and instead of paying money to power company, I transfer it there.
Yes, there will always be depreciation costs for any system for it's use over the period of 15 years, however if I DO NOT have this system then the money I am going to pay (2400 more per year) to the Power company is never going to come back to me.
So I can assume my depreciated hardware (if it's still working in the warranty period) is possibly better than paying money that I will never get back.
If I get 15 years of service from the system (warranty period of the actual system) - fairly confident that it will cover my capital costs.
Although, I might end up selling the property in 5 years, which is when I will expect to get my capitol to be returned partially.
It's like having a pool / spa in your backyard to increase your value (use it or not)? in my case I use it heavily.
About opportunity cost
I do have money aside for any opportunity cost, but I "personally" would not like to compare one to another. Each to their own have their risks and benefits. This 30k I borrowed is on a seperate account paying itself by discounting my powerbill and possibly more by my EV use.
Fair comment on the money you save on power bills being used to pay the principal.
Based on your 15 year life expectancy when you consider capital and interest alone, the way I add it up, you are paying $3200 per year to save paying the power company $2400 per year plus or minus. ($30,000/15 = $2000/year, plus $1200 interest/year.) I guess the interest figure will go down as the principal diminishes.
Obviously you have worked the numbers differently.
As you said it like having a swimming pool or spa.
Sorry to everyone else for going slightly off topic.