Victron battery on a dynamic tariff: what it really saves

How we calculated

The basis is a year of real hourly data (2025) from the Victron VRM portal: consumption, PV production, grid import and feed-in. Added to that are the day-ahead market prices for Germany (EPEX, bidding zone DE-LU) for every hour of the year.

We set the retail price of a dynamic tariff at the market price plus 19 ct for grid fees, levies and margin, plus 19 % VAT. That averages about 33 ct/kWh over the year. Feed-in is valued at 7.9 ct, and at zero in hours with a negative market price.

The controller replans the next 36 hours every hour, with forecasts that are as wrong as in real operation: consumption from the last seven days, PV with a random daily error, next-day market prices known only from about 13:00. The comparison is a normally configured Victron ESS.

The result: around 5 % of the electricity bill

A typical family house with 11 MWh a year (household, heat pump, electric car), 10 kWp of PV and a 15 kWh battery saves around 100 € a year with smart control and a dynamic tariff. A large house with 39 MWh and a 79 kWh battery saves around 330 €.

Both are about 5 % of the electricity bill. With a flat tariff the battery control saves practically nothing: without price differences there is nothing to shift, and a normally configured ESS already does the right thing.

Why the battery alone brings so little

The market price often swings by 10 to 20 ct over a day. For the end customer, however, a large part of the price is fixed: grid fees, electricity tax, levies and margin are added to every kilowatt hour alike. The percentage spread is therefore much smaller than the market curve suggests.

Then there is efficiency: every kilowatt hour that passes through the battery loses around 10 % on the round trip. And on sunny days the battery is full of solar power anyway, so there is nothing to recharge cheaply.

Where the money really is: the car

The largest part of the savings comes from charging the car. Whoever plugs in at 18:00 and charges right away hits the most expensive hour of the day. If the controller shifts the charge into the cheapest night hours before departure, charging costs in our calculation fall by about 7 %, around 65 € on 2,500 kWh a year.

The heat pump can be shifted in a similar way if the house can store heat, for example in underfloor heating or a buffer tank.

Is a dynamic tariff worth it for me?

A dynamic tariff pays off above all if you have large flexible loads: an electric car, a heat pump and a battery that is controlled automatically by price. Without control, a dynamic tariff can even be more expensive than a good fixed price, especially in winter when the heat pump runs a lot and the market is expensive.

• Battery alone on a flat price: hardly any savings from control.
• Dynamic tariff with car and heat pump: around 5 % of the electricity bill.
• The biggest win is moving the car into the cheapest night hours.