Yes and no. We don't know what the future holds. One example is the ever rising difficulty, decreasing the income/kWh.
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So.. the "formula" is more complicated and not as easily predictable.
The formula is pretty simple, as you start from solid base you will not be able to spend more on energy than you get in reward.
Here is one pretty good thanks to burtwAlso, what do you mean by the increase in difficulty?
The increase in difficulty is an effect of the increase in reward, remember that last year at 10k we were doing 100 Exahash, now we're doing barely double with 5 times the reward, the consumption is barely keeping up with the price because of chip shortage that leads to both Bitmain and MicroBT get sold out even if customers are ready to pay triple the price.
I've got an insane deal buying 3 miners at just 2 and a half the price of last summer, if enough mienrs would be available at this moment you will see difficulty do another x2 in a month.