Energy: Add monthly advance and adjust for daily/yearly

In the Netherlands, we usually pay a monthly advance to our energy provider, which is then, after a year, calculated versus what we actually consumed on energy/gas and the difference is then charged/returned.

With the data we have available in HA, this should, in theory, also be possible to calculate, and keep the historical data as well, to be able to compare against previous years.

My thinking for this would be:
As a first iteration:
Add a “Monthly Advance” to the Energy Dashboard configuration. Let’s say (for calculation purposes), this is €300.
The “Daily” cost would then be 300/30=€10, which you would only be able to see the day after, as that is when you know the actual cost.
You can then offset this against the monthly/yearly view as well, so you can extrapolate to see if you will be spending more or less on energy, and act accordingly.
Calculation above is of course based on the number of days in the month, but that shouldn’t be too hard, I guess.

The first iteration does not take into account the seasonal adjustments that you would expect. For instance: In the winter months, the expected costs would be higher, as you would consume more gas/electricity to heat your house.

Hope this makes sense