Margins, Fees, Taxes and More Fees on dynamic electricity price

[RenatusRo]

As tariffs are trending today yet another perspective:

None of the Belgian energy companies provides an API. Prices are given as formulas based on the belpex market index X

grid:
  marginA * X + marginB
feedin:
  marginC * X - marginD

The final grid: price/kWh then becomes (marginA * X + marginB + various_fees) * VATaxThing + MoreFees

MoreFees being a composition of capacity tariff + fixed provider fee broken down to an estimation per kWh based on year demand an average capacity.

Describe the solution you'd like

A possibility to describe a tariff formula based on entsoe.

Describe alternatives you've considered

The current entsoe/charges/tax gives a good start but stays a bit off the reality. And using @VolkerK62 nice life hack https://github.com/evcc-io/evcc/discussions/16465#discussioncomment-10839844 looks cumbersome. Of course I could build a day ahead price array myself outside evcc and do a type: custom to myself.

[andig]

We already have charges and taxes. Aren't they sufficient? What tariff are we even talking about here?

[RenatusRo]

At least Margin is missing:

AFAIK now it is

func (t *embed) totalPrice(price float64) float64 {
    return (price + t.Charges) * (1 + t.Tax)
}

for grid we would need

func (t *embed) totalPrice(price float64) float64 {
    return ((t.Margin* price + t.Charges) * (1 + t.Tax)) + t.MoreFees
}

t.Margin, t.Charges being specific for grid. o.k, t.MoreFees could be calculated into t.Charges

and for feedin

func (t *embed) totalPrice(price float64) float64 {
    return ((t.Margin* price + t.Charges)
}

t.Margin, t.Charges being specific for feedin

[andig]

I don't understand:

• are you saying you need to be able to calculate charges as percentage instead of fixed value (and call that margin)
• and that there are additional non-taxable uplifts

What tariff are we even talking about here?

[RenatusRo]

exactly, charges as percentage and non-taxable uplifts. ( https://trevion.be/tariefkaarten/ )

[andig]

I tend to revert this and replace this PR with the ability to define an arbitrary formula (using Go syntax):

math.Abs(price) * 1.19 + 0.32

If we do that we need to understand which and how many variables need to go into that formula and if the variables are fixed or zone-based (see https://github.com/evcc-io/evcc/issues/16829).