The cloudmining comparison sheet -- HELP ME WITH A FORMULA AND GET REWARDED!!

cloudmining comparison sheet
There are many different cloud mining companies with many different offerings. You often pay per Terra hash, but you never know how much 1 TH will deliver you per day, as this varies a lot per company. Of course you just want to have the best deal and trust the company you invest in. To help people make this decision I decided to test all options and compare them in a google sheet so everyone can see and share it. Check it out:

http://bit.ly/2uT3705

In the sheet I compare the daily income per TH/S per company and then calculate the expected break even point. I will keep updating the sheet so you can know for sure at any time which companies gives you the best bang for your buck!

When you open the sheet, you see that the cost for a Hashflare contract per TH/S, is 80 usd, in cell E11. The daily profit for this contract per TH/S is $0.21 at the time of writing, which gives a break even point of 378 days (cell E18). In this calculation I assume the bitcoin price and difficulty price will stay the same during that whole period, which is never the case.

Price VS Difficulty
To make an estimation of the potential future increase in price and difficulty, I made a comparison of the price VS difficulty going all the way back until 2010. In this tab I made various calculations which show the daily compound and average growth rate of both the price and difficulty from various points in time.

The sheet allows you to pick a beginning and end date for both the price and difficulty (cell B3:C4). It will then return the compound and average growth rates for the price and difficulty* between these two points in time. These growth rates then get used for the advanced calculations tab in which the sheet calculates the return on investment of the various contracts while assuming the price and difficulty increases with the same rate as it did in the time frame in history picked by you! When you copy or download the sheet you can edit it yourself and thus can also just manually fill in the growth rates according to your estimations.
*To use this data for calculations you need to know your mining profit decrease rate rather than the difficulty increase rate. The mining decrease rate equals 1/(1+diff increase rate) which is why I added cell D7 & D8

Example:
Lets say you expect the price and difficulty to increase at the same rate as it did during last year. To calculate the growth rates between this time period, You have to fill in the date of exactly a year ago in cell B3 and C3, the current date in cell B4 and C4. The sheet then automatically calculates the growth rates between this time period and uses the compound growth rate for the calculations in the advanced calculation sheet.

The challenge
There is however unfortunately one missing cell in the advanced calculation sheet. In row from C20, I put a formula in which I can pick an amount of days to which the the cell returns the corresponding total profits (assuming the price and difficulty increase at the compound growth rate determined in the price vs difficulty tab).

To calculate the expected days until you make a return on investment, I now have to change this amount of days until the returned amount is higher than the cost price of the contract (cell C10). I am looking for a formula that automatically does this without any need for manual input. I know it is very likely a formula that involves Σ however I don't know how to find or apply the Σ in google sheets.

I know that it isn't an easy task, but if I have this formula I can make interesting income predictions for all cloudmining companies which we could all benefit from 🙂 I will also test and compare companies on request.
I offer 25 USD worth of steem and a personal mention in the sheet for the person that knows the answer and can tell me the exact formula to get this done! (I know its not that much, unfortunately I'm just a poor student haha).

I hope that what I want is possible and that someone can help me!
Please share, upvote and resteem! The more people who see this post, the higher the chance someone can help me and we will all have a cool cloudmining comparison sheet! I will test other cloudmining companies on demand and compare them to the others in the sheet. If you have any more questions let me know in the comments so I can clarify it for everyone.

Follow me for more cloudmining cryptotrading and blockchain fundamentals content!

Cheers,
Rafael
https://steemit.com/@circularitylabs
circularitylabs.com