There are two major ways to view an investment of this type. First, as you've done, as a capital investment with a certain expected return on investment. Second, the buying power of the Bitcoin your system would mine increasing about 170% per year on average in US dollar terms.

But mind you, your business wouldn't practically be Bitcoin mining, but electricity production and then selling that electricity in the way that makes the most economic sense. The real question is, how efficient is your capital expenditure in producing kilowatts per hour? At that point, once your solar system is up and going, you can sell your electricity to whoever will pay the best price for it.

You are effectively saying you want to sell your electricity to the Bitcoin network for the sats they will pay you for it, and that option may work for you. However, that isn't your only option. My wife and I sell the electricity from our solar system to whoever will pay us the best rate for it, all things being equal. For us this means mining whatever crapcoin is most profitable, and then getting paid in Bitcoin. All that to say, your real business is electricity production and sales using solar, if that's the best way for you to produce it. I hope this makes sense.