Hello folks,
In the configuration of DESS settings, on the VRM portal and in the documentation, the units used are not always very clear.

Energy contracts (in Belgium) typically use €c/kWh.
eSpot (P) prices (for Belgium) are typically in €/MWh.
It seems that Victron DESS is using prices in €/kWh.

Can somebody confirm the price unit used by Victron DESS internally ?

This can have a hefty impact on price calculations, especially when counting the extra grid and federal fees for Belgium.

FYI: Here are the Buy/Sell formulas for the latest ‘Engie Dynamic’ contract, with everything corrected to use €/kWh.

Sell to grid: (P * 0.001)-0.00905
Buy from grid: ((0.01395+(P * 0.001))*1.06)+0.01582+0.0523708+0.053861 (price in €/kWh)

The 2nd to last component in the Buy formula are the Federal taxes and those are fixed for everybody.
The last component is the ‘grid cost’ and this one varies, depending who the local distributor is.
Price for the ‘Green Energy’ option is not in the formula.
The ‘Capacity Tariff’ is not taken into account either as this is calculated yearly and depends on both the quarter peak usage (in kW) and the total annual consumption (in kWh).

But the Victron API will provide the correct “P”, so unless you are really only paying one promile of the current netprice, you don’t have to do that * 0.001

I don’t know the exact formula for your country / vendor - but in my formula, i’m considering the p to be Eur/kWh, and the final chart generated by DESS matches the actual prices exactly.

Taking the P from DESS in kWh instead of MWh like the vendor does and compensating the other variables accordingly, the prices produced by DESS now match perfectly with what my Excel file calculates. Seems that last night I was a bit more tired than I thought.
Thanks for pointing me in the right direction !

Pricing in Belgium is crazy, we have a component for the vendor, the distributor and the government. And the Capacity aka Peak Power part, which isn’t supported yet by DESS.

I suspect that’s the “x 1.19” component.
If I’m not mistaken, VAT in Germany is 19%
In Belgium, VAT on electricity is 6% for individuals and 21% for companies, hence the “x 1.06” in my formula.
On injected energy, no VAT for individuals so there it’s just the provider’s formula.
The 3 weird additions in my Buy formula are for taxes/kWh, VAT included, for different entities.
I didn’t simply add them all up because some of them vary on the energy provider and distributor.
The yearly cost of subscription and Capacity (peak power usage) are not accounted for.

We do, but the network fee is “fixed” per kWh. So is the vat (and included in the 18 cents).
Only the VAT on the spot price is therefore required in the formula.

As a Tibber customer, you get a very precise breakdown of your costs. I think you should be precise there. Otherwise, you don’t need to ask anywhere else how exactly DESS calculates the costs.

It is precise enough, as you can see. The offset within usual price ranges is 0.2 cent (not 0.2 Eur). Nothing to worry about, DESS does not even show that part of the price.