Price fixing and price guarantee are two different promises
Price fixing means the per-kilowatt-hour energy rate is contractually locked for the term of the contract. Your supplier carries the risk that wholesale prices rise during that period; you pay the agreed rate regardless of what happens on the exchange.
A price guarantee is narrower: it is a promise that the supplier will not increase the price for a stated window. The key question is always what the guarantee covers — the pure energy component, or also the pass-through parts such as grid fees, taxes and levies, which a supplier generally cannot control. Reading which components are inside the guarantee matters more than the label on the tariff.
Fixed-price versus variable and dynamic tariffs
The German market offers both fixed-price tariffs and flexible, dynamic tariffs. A fixed-price tariff is chosen mainly for planning security: you know your rate in advance and can budget against it.
Dynamic and variable tariffs are a comparatively recent development, but they are gaining importance and availability. Instead of a locked rate they pass wholesale price movements through to the customer, which shifts both the risk and the opportunity of price changes onto the consumer. The trade-off is straightforward — a fixed price removes uncertainty, a dynamic price exposes you to it in both directions.
The day-ahead market sets the price underneath both
Whether you sign a fixed price or a dynamic one, the reference is the wholesale exchange. Stromfee's "Strompreise live" tool publishes the exchange electricity prices for today and tomorrow, hourly, free and without registration — the same day-ahead prices that suppliers use to hedge fixed-rate contracts.
The wholesale layer is not a single number. It is a sequence of trading stages: the day-ahead auction sets an hourly price the afternoon before delivery, an intraday auction lets participants correct that allocation with a fresher forecast, and continuous intraday trading (settled at volume-weighted average price) handles many small trades closer to delivery. A supplier offering you a fixed price is, in effect, buying across these stages so it can hold your rate steady.
Why a fixed price still has to be traded every day
Locking a customer's price does not remove the volatility — it moves the volatility to the supplier, who must cover its position on the exchange. Deviations between the volume a supplier contracted and what its customers actually consume are settled as imbalance energy (reBAP), which is a cost or a credit depending on the direction of the error.
This is where day-ahead and intraday strategy matters. Accurate forecasting and disciplined trading across the day-ahead auction, intraday auction and continuous intraday reduce the imbalance exposure that would otherwise sit behind a fixed-price promise. The quality of a price guarantee is therefore partly a function of how well the underlying position is managed, not only of the contract wording.
Flexibility as a hedge: batteries and reserved capacity
Beyond the tariff, physical flexibility changes the price picture. A battery can arbitrage the day-ahead spread — charging in low-price hours and discharging in high-price hours — turning wholesale volatility into revenue rather than only cost.
A battery can also earn from reserving power rather than moving energy. In frequency containment reserve (FCR), the revenue comes from holding capacity available symmetrically, not from arbitrage; Stromfee's academy cites an FCR value of 14,332 €/MW for May 2026, with a derating of roughly 0.83 applied for state-of-charge management. Direct marketers stack these balancing revenues on top of spot-market arbitrage. For a consumer or operator, that stacked income can offset the price they pay under a fixed or dynamic contract.
Contract terms differ by market design
What a price guarantee can offer depends on how the local market is built. Germany's day-ahead and intraday markets, plus balancing products such as FCR, aFRR and mFRR, give suppliers several layers to hedge a fixed price.
Other markets are structured differently. The California ISO runs day-ahead and real-time energy and ancillary-services markets but no centralized capacity auction; resource adequacy is handled separately through a regulator-administered program. A price arrangement that leans on capacity revenue in one market may have no equivalent in another, so a guarantee written for one market design does not transfer unchanged to another.
FAQ
Is a price guarantee the same as a fixed price?
No. A fixed price locks the per-kilowatt-hour energy rate for the contract term. A price guarantee is a promise not to raise the price for a stated period, and it may cover only part of the bill — often the energy component but not grid fees, taxes and levies. Always check which components the guarantee includes.
Should I choose a fixed or a dynamic tariff?
A fixed-price tariff gives planning security: you know your rate in advance. Dynamic and variable tariffs, a newer but growing option, pass wholesale price movements through to you, exposing you to both higher and lower prices. The right choice depends on whether you want predictability or are willing to carry price risk for potential savings.
Where can I see the wholesale price my tariff is based on?
Stromfee's "Strompreise live" tool shows the exchange electricity prices for today and tomorrow, hourly, free and without registration. These are the day-ahead prices suppliers use as the reference for both fixed and dynamic tariffs.
How does a supplier hold a fixed price steady?
It hedges the position on the wholesale market across the day-ahead auction, intraday auction and continuous intraday trading. Gaps between contracted and actual consumption are settled as imbalance energy (reBAP), so accurate forecasting and trading discipline determine how sustainable a fixed-price offer really is.