What the power price actually refers to
The figure quoted as "the power price" in market reports is the wholesale spot price: the price at which electricity is traded for delivery in a specific hour, in a specific bidding zone. Stromfee's Energy Core dashboard reports it for DE_LU (the German-Luxembourg zone) — for example €72/MWh, up 8.2% on the previous reading, within a 24-hour band of €28 to €145/MWh.
This is not the price a household or a small business pays. Retail tariffs add network charges, levies, taxes and supplier margin on top, and they are usually flat. The wholesale price is the part that moves — and the only part a storage operator or a flexible consumer can trade against. Everything below refers to the wholesale number.
Why the price moves so much within a single day
Prices are set hour by hour against demand and available supply. When solar output is high, low-marginal-cost generation covers a large share of demand and the price falls. In the Stromfee dashboard's snapshot, a 400 kWp PV system producing 285 kW is covering 71% of its capacity — the kind of midday output that pushes zone-wide prices toward the bottom of the daily range. In the evening, solar drops out while demand stays high, and the price climbs toward the day's peak.
Weather drives the shape directly. Stromfee's French market page pairs each day's prices with the local conditions: on 2026-07-15, with Paris at 21°C and a 21–33°C daily range, cooling demand lifted the evening peaks. That day's French day-ahead prices averaged €139/MWh, ranging from €88 to €202/MWh, with zero negative hours.
The floor is not always zero. When inflexible generation exceeds demand, day-ahead prices go negative and producers pay to deliver. Stromfee's market pages count negative hours explicitly for each day precisely because those hours change the economics of both feed-in and storage.
The spread is the tradable quantity
For anyone with flexibility, the useful number is not the price level but the spread — the difference between the cheapest and the most expensive hours of the same day. In the Energy Core snapshot, a current spread of €44 was enough for the trading assistant to flag an optimal discharge window approaching between 17:00 and 19:00, with a peak price forecast of €145/MWh at 18:00.
A wide spread means charging cheap and discharging expensive is worth doing. A narrow one means the round-trip losses and the cycle wear eat the margin. This is why a storage business case is built on the daily spread distribution over a year, not on an average price: an average of €139/MWh tells you nothing about whether the €88 hour and the €202 hour were on the same day.
What a battery can capture: the perfect-foresight ceiling
Stromfee's market pages publish a "battery ceiling" figure for a 1 MW battery — what that battery would have earned with a perfect price forecast, on that day's actual prices. It is an upper bound, not a projection. Nobody knows tomorrow's prices exactly, so real arbitrage revenue lands below the ceiling; the gap between the two is the honest measure of how good the forecasting and dispatch are.
The point of publishing the ceiling is calibration. If a day's ceiling is small because the spread was flat, no amount of clever dispatch would have helped. If the ceiling is large and the realised revenue is not, the dispatch logic is the problem. The Energy Core dashboard shows the same logic on the operational side: a 500 kWh BESS at 68% state of charge, discharging at 125 kW, with €47.20 earned on the day.
PV plus storage: shifting the surplus into the peak
The most direct application is to stop exporting solar into the hours when it is worth least. In the Stromfee dashboard's market intel, strong solar production of 285 kW prompts the recommendation to store excess via PV→BESS in order to capture the evening peak — moving energy from a low-price hour into the €145/MWh forecast hour at 18:00.
The Energy Hub 3D visualisation shows the same variables an operator watches together: 2.4 MW of wind, 847 kW of solar PV, a 72% battery state of charge, and a spot price of 64 €/MWh, alongside the 24-hour price curve, PV generation, battery SOC and grid load. Dispatch decisions depend on all of them at once — the price alone does not tell you whether the battery has the energy or the headroom to act on it.
Power price is a local concept: markets differ by design
A price is only meaningful with a market attached. Stromfee tracks US wholesale prices across five separate markets — PJM Interconnection across 13 eastern states, CAISO in California, MISO in the Midcontinent, ERCOT in Texas and ISO-NE in New England — because a price in one says little about a price in another.
Market design changes what the price can do. ERCOT runs an energy-only wholesale market with no capacity market: generators are paid only for the energy they produce, not for being available. Resource adequacy relies on scarcity pricing through the Operating Reserve Demand Curve, which adds a reserve adder that can push real-time prices to the system-wide offer cap. The Public Utility Commission of Texas lowered that cap from $9,000/MWh to $5,000/MWh after the February 2021 winter storm. A cap of that size means the arbitrage value in ERCOT is concentrated in very few hours per year — a fundamentally different storage business case from the daily-spread pattern of DE_LU.
FAQ
Is €72/MWh a high or a low power price?
Neither on its own — it depends on the day's range. The Stromfee Energy Core snapshot showing €72/MWh also shows a 24-hour band of €28 to €145/MWh, so €72 sits in the middle. On the French market on 2026-07-15, the day averaged €139/MWh with a €88–€202/MWh range, and €72 would have been below every hour traded. Always read the price against the range, not against a remembered number.
What is the difference between the power price and my electricity bill?
The wholesale spot price is one component of a retail bill, alongside network charges, levies, taxes and supplier margin. Wholesale prices change every hour; most retail tariffs do not. Storage arbitrage acts on the wholesale component, which is why the operating figures on the Stromfee dashboard — spot price, spread, state of charge — are all quoted in €/MWh rather than in cents per kWh on a bill.
How large does a spread have to be before storage arbitrage pays?
There is no single threshold, because it depends on round-trip efficiency, cycle cost and how often that spread recurs. What can be measured is the upper bound: Stromfee's market pages publish, for each day, what a 1 MW battery would have earned with a perfect forecast on that day's actual prices. Compare a candidate system's costs against that ceiling over a full year of days — a single good day proves nothing.
Why does Stromfee count negative price hours separately?
Because negative hours invert the normal logic: producers pay to deliver, so exporting is a loss and charging a battery earns money instead of costing it. The count is reported per day — the French market page recorded zero negative hours on 2026-07-15 — because their frequency, not just the average price, determines how a PV-plus-storage system should be dispatched.
