I’m only half kidding. I’m a bit of a prepper and I have lots of powerbanks and devices that charge from USB but besides idling my truck I really had no other way to charge any of them in case of a long-term power outage which seemed a bit of an oversight on my part.
Not like this solves the issue. 30 watts (under ideal conditions) isn’t much but it’s a start.


Time, in hours (H), equals average solar kilowatt hours per month (K), multiplied by the price of one kilowatt hour (P), divided by the total cost © of all the purchased components.
H = (K * P) / C
I’m sure if you were patient and dedicated enough, you could approximate each of those numbers using the info OP has already posted and get a general idea (weeks, months, or years).
So you’re dividing the average saving per month by the total cost and expecting to get hours?
If we generously estimate a very high 3000kWh/month generated and high $0.40/kWh price and it cost OP $9000, then you formula is (3000×0.40)/9000 = 0.133 hours.
Breaking even after less than 1 hour?!??! Extraordinary!
It’s pretty easy to cry about bad math, but it’s a lot harder to figure out the right math.
Don’t worry, I’ll try to do it for you again a second time.
Power consumption varies. Use the average monthly power draw from the solar array, let’s assume for demonstration purposes 1,000 kWh/month.
Multiply that by the cost of 1 kWh from the power company, let’s say 20 cents.
In one month, that means you saved $200.
Let’s assume the solar equipment costs $1,000.
The answer is 5 months, or 5,000 kWh.
Sorry, I’ll make sure the free work I do for you is better quality next time.
Bro. Don’t act like this basic arithmetic and unit cancelation is hard. Not my fault you were so confidently incorrect.
Or I could read the comment where he said
Then do that instead of asking random people who aren’t in any position to know.
It was more of a comment on your comment