What is the ROI of investing solar panels
And I’m not talking for personal use that’s not scalable to bigger numbers but real solar energy farm.
Mining Bitcoins
This is the first use case I came because it’s just possible for anyone to do it simply without figuring out how you get the solar panels to the grid where other people can buy the electricity.
- What’s the best price quality ratio solar panel?
Most Affordable Solar Panels | LetsGoSolar.com
ReneSola JC255M-24/Bb costs $173.40 and it makes 255W. I don’t have much knowledge about these but I assume this is the max it can be in the perfect sun and otherwise it’s going to be less.
- Hash rate per Watt
Hash rate is something that changes between the coins because there are different algorithms. That is why it’s important to calculate hash rate for each crypto currency. I’m a little bit lazy so I just picked one GPU from here…
Best mining GPU 2020: the best graphics cards for mining Bitcoin, Ethereum and more
AMD Radeon VII (takes a little bit more power than the solar panel offers)
…and then I used this calculator…
…to see how much it makes.

It’s $580.35 a year.
It sounds way too high so I looked online if others got similar amount of money from this GPU.
Mining with AMD Radeon VII — BetterHash Calculator
AMD Radeon VII mining calculator ⛏️ | minerstat
It looks about right.
Okay what’s the ROI then? First we need to understand how long GPU and solar panel last.
There is two year warranty in this GPU which means that it’s the least minimum. Then often people say that the fans break so maybe it’s fair to give 4 years life time expectation for a GPU in mining purpose.
Solar panels last much longer so let’s give pretty conservative 10 years.
This makes solar panel cost around $20 a year and GPU cost $700/4 = $175.
The final thing to turn this optimal case into something closer to the real world. The sun is not going to shine 24 hours perfectly to the solar panel.
I’m not very good with electricity calculations but I found some articles that talked about this topic.
kW, kWh and kilowatt/hour : What does it all mean?
This confirmed that kWh is just how many kW is used in hour. In this case GPU used 300W which means that it’s 0.3kWh.
I found that some car battery was 100Ah.
Because Power in Watts = Current in Amps x Voltage I can calculate that with 12V it offers 1,200W. This means that it’s going to run 300W system for 4 hours.
I’m highly suspicious that this is correct but it’s probably close enough. Based on the result I need around 300Ah to run 12 hours which is half of the day. Because the sun is not 12 hours a day shining it means that it’s probably better to play safe and have 400Ah. This cost $400 which is pretty big expense especially when the batteries often doesn’t last long. I assume that there are better than car batteries for this that are cheaper so it should offer some margin of error.
Conclusion
Based on this AMD Radeon VII GPU produce $580.35 a year.
It consumes 300W power which should be supplied from solar panels. 300W solar panel cost a little bit less than $200. One solar panel is not enough because it’s probably working in the maximum performance very rarely and the average hourly watts are much much less. So let’s say that three 300W solar panels is needed.
Battery needs to be 400Ah based on my sloppy calculations. This cost around $400.

With these calculations I tried to be conservative to get some margin for an error. I have learned from programming to calculate the worst case scenario. It’s useful to use it because then the investment is going to be something higher than that and makes totally sense if the worst case makes sense.
Based on this, mining crypto currency with solar power should make around
profit = $580.35 — $335 = $245.35
ROI = $245.35/$335 = 73%
This means that every dollar I put to this investment should product $1.73 back a year.
Now of course I can’t just do any conclusion without looking some conclusions other people have made.
First of all I started by researching how many kWh solar panels produce in Finland on average.
Hyödyllistä tietoa aurinkopaneeleista
Based on this 3kW solar panel produces around 2,500 kWh a year. This means that 300W panel makes 250 kWh.
250 000 Wh / 300 W = 833h
365 * 24h = 8,760h
So to produce year worth of electricity for a GPU requires 3 kW panel. It’s 3 times more what I calculated. The biggest problem probably is that 70% is produced between March and September requiring huge batteries to store the electricity for the winter. The best solution is probably just mine summers or at least reduce the mining for winters.
Sähkön hinta — mitä kWh maksaa ja mitä sillä saa
Based on this Finnish article, the cost of electricity here in Helsinki is around 0.05e-0.07e. That’s actually pretty cheap and with the calculator I can see that it makes almost the same amount of profit as solar panel.
It doesn’t actually make any sense to use solar panel when electricity is such a cheap. It saves a lot of time and reduces the probability for breaking devices. And here it’s even better because sun is not shining evenly but there is much more light in summer and almost non in winter.
When I looked some other prices in United States it seems like the cost of electricity is pretty low here.
Average Energy Prices, New York-Newark-Jersey City — May 2018