I bought SONOFF POW 2 And I found that when you set price in SETTINGS - ELECTRICITY RATES by less than 1.00 in ELECTRICITY RECORD in ELECTRICITY FEE is the wrong result. Is obtained at price 1.11 too.
When you set a price of 1 or a higher number without cents, the calculations are correct.
The calculation formula should be reworked
In my country, a cost of 1 KW is 0.15 and there is no true result.
I think it will be the same in other countries as well.