Usually electricity is metered separately, exported energy is credited nothing or peanuts.
Given energy tariffs vary widely all around the world I wouldn't make assumptions about such things. Some people (the number is dwindling) still receive more per kWh for their PV exports than their import tariffs.
For us it costs between 20c/kWh to 61c/kWh to purchase from the grid while our exports are credited at 12c/kWh.
But if we can't
reasonably consume our PV output, then at least I still get some credit for the excess. It helps to cover the daily service charge.
I see little point in consumption for consumption's sake.
So you cannot make simple arithmetic with KWh unless you really have an old Ferraris meter.
Who said I was?
I know precisely what the impact on our billing is.
Summer here has been very hot and humid and our energy consumption for air conditioning has been higher than normal. We also added an EV at the end of September so that has seen our consumption and self-consumption rate increase.
In April 2022 I moved our water heater over to use a smart PV diverter such that it is all but 100% powered by solar PV, and added the off-grid battery system as well so that much of our evening / overnight consumption is also covered by solar PV generation.
Not everything though, in particular our ducted aircon system which still requires some grid energy, especially at night.
Over enough time, yes.
As I said, that was our PV generation since 1 December 2023 through to yesterday.
In 2023 we generated a total of 17.3 MWh.