This chart shows the Breakeven Efficiency required for both Monero and Bitcoin calculated at energy cost of $0.10/KWh.
This is the minimum efficiency you would need to mine profitably (mining income >= electricity cost) at any given moment.
This value is directly proportional to your electricity cost: for example, if your energy cost is $0.20/KWh, just multiply the value on the chart by 2.
That will give you the number of H/s you must produce for each Watt of electricity you consume.
In simple words, divide your hashrate (H/s) by your power consumption at the wall (Watts);
if this number is bigger than the latest Breakeven efficiency on the chart, then you are mining at a profit; otherwise, you are mining at a loss.