Heat Pump Control on a Dynamic Electricity Tariff (Spot Market Optimisation)

The heat pump charges thermal storage preferentially during low-price hours (EPEX spot, dynamic tariffs) — cutting electricity costs by 15-30 %.

How does heat pump control with a dynamic electricity tariff work?

With a dynamic electricity tariff, the unit price is not fixed but follows the hourly exchange price on the spot market (EPEX Spot). Prices fluctuate considerably over the course of the day: with plenty of wind and solar power they are low, in the evening hours high. A heat pump is an ideal flexible load because heat can be stored cheaply. The controller reads in the price forecast for the following day and shifts operation into the cheap hours: the buffer tank or – with thermally activated building systems – the building mass is overheated by about 5 K, and during expensive hours the heat pump stays off while the storage releases heat passively. Enabling is via the SG-Ready interface or Modbus. In Austria, this requires a smart meter with activated 15-minute readings; since 2025, every electricity supplier has been obliged to offer a dynamic tariff.

Which buildings benefit from spot market optimisation?

Suitable are detached houses with heat pump and buffer tank, apartment buildings with a central heat pump, and office buildings with thermally activated building systems whose storage mass bridges several hours. Requirements are a smart meter, a spot tariff from the electricity supplier and a heat pump with an external enable or control input. The larger the storage capacity and the lower the flow temperature, the more hours can be shifted. Direct electric heating without storage is not suitable. The saving potential grows with price volatility on the electricity market, which tends to increase with the expansion of renewable energy.

What does a dynamic electricity tariff actually deliver for a heat pump?

The heat pump's electricity costs fall by 15 to 30 %. A detached house with 5,000 kWh of heat pump electricity saves around 200 € per year if the average purchase price is reduced from 0.22 to 0.18 €/kWh; for larger systems, the benefit scales linearly. As a side effect, the CO2 factor of the electricity purchased falls, because low-price hours usually coincide with a high share of renewable generation. Costs for controller and tariff module are 800 to 2,500 €; a buffer tank is usually already in place. Over a 12-year service life, payback is 4 to 10 years.

Energy carrier

Strom (Festtarif) → Strom (Spot-Tarif optimiert)

Savings potential

15-30 % Stromkosten WP

Worked example

A detached house is heated by a heat pump with buffer tank that consumes 5,000 kWh of electricity per year. Until now, the household has bought electricity on a fixed tariff; on a dynamic tariff, the average price including grid charges and levies would be 0.22 €/kWh if the heat pump continued to run demand-led as before. After switching to a spot tariff and retrofitting a controller that reads in the next day's price forecast, the heat pump shifts its operation into the cheap hours and pre-charges the buffer tank by about 5 K in the process. This reduces the achievable average price of heat pump electricity to 0.18 €/kWh. The cost advantage is 5,000 × (0.22 − 0.18) = 200 € per year. At a cost of 800 to 2,500 € for controller and tariff module, the measure pays back in 4 to 10 years; for apartment buildings or commercial buildings with a larger heat pump, the benefit scales linearly with electricity consumption.

Investment & payback

Smart-Steuerung + Tarifmodul: 800-2.500 €; Pufferspeicher meist vorhanden · Service life: 12 a · Payback: 4-10 a

Applicability

Requirements

Exclusion criteria

Typical buildings

Frequently asked questions

Is a dynamic electricity tariff worthwhile for a heat pump?

A dynamic electricity tariff is worthwhile for heat pumps with a buffer tank or thermally activated building systems, because operation can be shifted into cheap hours. The heat pump's electricity costs fall by 15 to 30 % as a result; with an annual consumption of 5,000 kWh, that is around 200 € per year. Without storage and automatic control, the benefit is small, and during high-price periods the tariff can be more expensive than a fixed price.

What do you need for a dynamic electricity tariff in Austria?

In Austria, a dynamic electricity tariff requires a smart meter with activated 15-minute readings, which is requested from the grid operator via opt-in. Since 2025, every electricity supplier has been obliged under the ElWOG amendment (Austrian Electricity Act) to offer a dynamic tariff. The heat pump also needs an external enable or control input, usually the SG-Ready interface or Modbus, plus a controller that processes the spot prices.

How much does the controller for spot market optimisation cost?

The controller for spot market optimisation costs 800 to 2,500 € including tariff module. A buffer tank is already present in most heat pump systems and does not need to be retrofitted. With a cost saving of 15 to 30 % on heat pump electricity, the investment pays back in 4 to 10 years. The controller's service life is assumed to be 12 years.

What is SG-Ready for heat pumps?

SG-Ready (Smart Grid Ready) is a standardised interface with two switching contacts through which a heat pump can be set externally to four operating states: block, normal operation, boosted operation and forced run. A controller for dynamic tariffs uses these contacts to prompt the heat pump to charge the storage during cheap hours and to block it during expensive hours. Most heat pumps sold since about 2013 are SG-Ready capable.

Does a dynamic electricity tariff also save CO2?

A dynamic electricity tariff can reduce a heat pump's CO2 emissions because low spot prices usually coincide with a high share of wind and solar power. Shifting operation into these hours means purchasing electricity with a lower average emission factor – estimated at about 0.130 instead of 0.156 kg CO2/kWh in the Austrian electricity mix. This effect is a side benefit; the main impact of the measure is on electricity costs, while energy consumption itself remains the same.

Related measures

Standards & sources

Metering points in the EDM Toolbox

EDM Toolbox kann Spot-Preise (ENTSO-E, EPEX) per API anbinden + Lastprofil WP + Pufferspeicher-Temperatur überlagern. Steuerimpulse via Modbus an WP. Bonus: Bewertung der Maßnahmen-Wirtschaftlichkeit täglich nachprüfbar.

All measures