Why the average price lies

The average price on your bill is the result of when the plant as a whole consumed. Applying it equally to every process assumes they all consume with the same hourly profile — and that is almost never true.

An example with round numbers. A plant with two processes consuming 100,000 kWh a month each: process A runs from 8:00 to 18:00 (solar hours, low prices); process B is a night shift with an evening peak (expensive hours). With an average bill price of €110/MWh, traditional accounting allocates €11,000 to each. Using the actual prices for each time slot, process A may have cost €7,500 and process B €14,500 — one nearly double the other, with identical consumption.

The consequences are not cosmetic: the product cost sheet for what B makes is understated (and A’s is penalised); efficiency investment is poorly prioritised, because a kWh saved isn’t worth the same in A as in B; and load shifting — the star lever of the quarter-hourly market — doesn’t even appear in the analysis, because the average price wipes it out by construction.

The right formula, layer by layer

The real cost of a process is built from three ingredients, from coarsest to finest:

1 · Its load profile — from submetering if you have it; if not yet, an estimate based on operating hours is the honest first step (and the reason to install metering wherever the load is significant).

2 · The price of each time slot. For indexed contracts, the quarter-hourly price from OMIE (the Iberian electricity market operator) plus the regulated components; for fixed contracts priced by period, the price of each tariff period P1–P6. In both cases, the energy charge stops being an average and becomes a sum: consumption in each quarter-hour × its price.

3 · The allocation of power and fixed costs. The capacity (power) charge is allocated not by kWh but by contribution to peak demand: the process that is running when the plant hits its maximum is the one that sizes the contracted power — and its excess power charges. Submetering tells you who was consuming in the quarter-hour of the monthly peak; without it, this allocation is impossible and the cost tends to be loaded unfairly onto the largest energy consumer, which is not always the one that sets the peak.

With all three layers, each process gets its cost in euros per month and per unit produced — and that second figure is the bridge to the third instalment of this series: efficiency indicators, on Friday.

What changes when the cost is real

Product cost sheets get corrected — sometimes by several percentage points for electricity-intensive products, enough to review pricing or the production mix.

Investments get re-prioritised: a battery, load shifting or heat recovery (in Spanish) are assessed against the cost of the hours they actually avoid, not against an average that dilutes them.

Internal conversations change tone: telling production ‘the plant uses a lot of energy’ changes nothing; showing them that their night shift costs twice as much per kWh as the morning shift opens a concrete negotiation about schedules and setpoints.

The PowerCloud view

Done by hand, this calculation is a heroic spreadsheet that gets abandoned by the second month. PowerCloud does it continuously: it cross-references the main meter and the submetering data with the actual quarter-hourly price in your contract, allocates the capacity charge by contribution to peak demand, and publishes the cost per process, per area and per unit produced — every day, without anyone having to rebuild it. Energy accounting stops being an annual estimate and becomes just another view of operations.

Do you know what your most important process really costs — in euros, not in kWh? We’ll calculate it for you using your actual load profile and your contract prices, and show you the difference compared with the average-price allocation you are probably using today. If you don’t have submetering yet, we start with the main meter’s load profile — we obtain it from Datadis (the official platform of Spain’s electricity distribution companies) with your authorisation. Diagnostic session: 30 minutes, no obligation.

Sources: OMIE (quarter-hourly prices); previous posts in this series and on the blog at powercloud.es/noticias/; Schneider Electric and Linkener (energy accounting practice with submetering).

La entrada How to calculate the real energy cost of each process: from the meter and submetering to euros per line se publicó primero en Powercloud | Energy monitoring and management.

It may look like a ‘technical’ change, but it actually marks a turning point in understanding (and optimising) energy in businesses, industry and self-consumption.

What exactly has changed?

Until now, the wholesale market (the ‘pool’) cleared one price for each hour of the day. Since the change:

• Each hour is divided into 4 slots: 00:00–00:15, 00:15–00:30, 00:30–00:45, 00:45–01:00, etc.
• So we move to 96 price periods a day.
• OMIE (the Iberian electricity market operator) already reflects this with periods such as H1Q1 (first quarter of the first hour), etc.  

And note the date: the ‘historic’ market clearing for the switch took place on 30 September 2025, already producing the 96 prices for energy delivered on 1 October.  

Why is this change happening? (the underlying reason)

The short answer: because the electricity system no longer behaves ‘by the hour’.

With renewables (solar and wind) carrying ever more weight, generation can vary considerably within a single hour. With prices every 15 minutes:

1. The price better reflects what it costs to produce electricity at each moment, matching supply and demand more precisely.  
2. Europe harmonises the electricity market through the EU single day-ahead coupling (SDAC), so that all countries ‘play’ with the same time unit.  
3. It is in step with the system’s shift towards finer balancing processes: Spain has also been adapting its imbalance settlement to 15 minutes, which is key for a more renewable and variable system.  

Who does it affect?

It depends on your type of contract and how your consumption is metered:

• Companies on a pool-indexed tariff: the ‘reference’ price becomes more granular (and therefore more opportunities to optimise appear… along with more intra-hour variability).
• Industry and consumers with a detailed load profile: this change has much more impact, because the real cost can differ within the same hour.
• Households: in practice, the immediate impact may be limited for many domestic users, depending on how the measure is applied and the effective granularity of meter reading/billing.  

What opportunities does it open up for a business?

This is where it gets interesting. With prices every 15 minutes, saving is no longer about ‘changing the hour’ but about ‘moving specific processes’:

• Shift flexible loads (HVAC, pumping, charging, staged furnaces, compressors, etc.) to cheaper quarter-hours.
• Detect micro-peaks: sometimes the expensive peak no longer lasts 1 hour… it lasts 15 minutes (and can be avoided).
• Optimise self-consumption and batteries: with finer time detail, you can better fine-tune when to use the grid, when to draw on the battery and when to charge it.
• Better analysis of €/unit produced (€/tonne, €/part, €/batch): if your production and energy data have fine resolution, the KPI improves enormously.

How does Powercloud approach it?

At Powercloud, this change translates into something very concrete: more precision to turn energy into euros, and euros into decisions.

Some practical ideas (very ‘shop-floor’):

• Energy cost per quarter-hour by line/process/site.
• Alerts if your consumption falls right in the most expensive quarter-hours of the day.
• Weekly comparisons: ‘my 10 most expensive quarter-hours’ vs ‘my 10 cheapest quarter-hours’.
• Business KPIs (€/t, €/unit) with better traceability.

Wrapping up

The quarter-hourly market is not a passing fad: it is the natural consequence of a more dynamic, more renewable and more European electricity system. And for businesses, it is a clear opportunity: if you can measure, you can understand; if you can understand, you can optimise.

If you like, in a future post we can bring this down to earth with a real example (e.g. a plant with compressors + self-consumption) and show which decisions emerge when you go from 24 to 96 prices a day.

La entrada Goodbye to ‘hourly’ prices: the electricity market now runs in quarter-hours (15 min) se publicó primero en Powercloud | Energy monitoring and management.