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Maxímetro: What it is and why it matters for SMEs (and large homes)

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A maxímetro is a measuring device that records the highest peak of electrical power used during a specific period without cutting off the supply. In Spain, this system is essential for SMEs and large homes with 3.0TD tariffs, as it prevents power outages when exceeding contracted limits while adjusting the final bill based on actual demand.

En 30 segundos

✓Locate the 'Billing Data' section in your PDF invoice.
✓Identify the 'Potencia Facturada' (Billed Power) vs 'Potencia Contratada' (Contracted Power).
✓Check if your billed power is consistently 85% of your contracted power (the minimum billing rule).

Stop paying for 'Ghost Power'

Our AI performs a forensic autopsy on your bill to see if your maxímetro readings suggest you should lower your contracted power.

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Free and no signup
AI trained on the Spanish market (~30s)
Privacy-first: ephemeral processing (we don't store your bills)

Transparencia y fuentes

Authorship, methodology and official sources.

Actualizado: 10 de enero de 2026

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Autoría

Equipo ahorr.ai

Auditoría energética (España)

Metodología orientada a decisión: separar coste fijo/variable, detectar extras y comparar opciones con números claros.

Metodología

→Separamos coste fijo (potencia/término fijo), energía y cargos/impuestos.
→Buscamos sobrecostes típicos: potencia sobredimensionada, servicios extra, lecturas estimadas.
→Damos pasos accionables (qué tocar primero) con ejemplos orientativos, no promesas.
→Enlazamos fuentes oficiales y marcamos lo que puede variar por comercializadora.

Fuentes oficiales

Información orientativa (España). Comprueba condiciones con tu comercializadora: precios, peajes, cargos e impuestos pueden variar.

What is a maxímetro: the definition without the jargon

Forget complex electrical engineering. The maxímetro is simply a 'high-water mark' for your electricity usage.

The definition in one sentence

A maxímetro is a device (integrated into modern meters) that records the maximum power you demand at any given time, allowing for billing based on actual peaks rather than just a fixed limit.

Where it appears on the bill

Look for the 'Potencia' or 'Lecturas' section. You will see values for P1, P2, P3 (and up to P6 in 3.0TD tariffs). Next to your 'Contracted' power, you'll see the 'Maximum Demand' or 'Maxímetro' reading.

Why it matters: money, decisions, and typical traps

In the Spanish market, the maxímetro is the heart of the 3.0TD tariff, used by most SMEs and large homes.

The most common error

Many businesses contract 'just in case' power. If you contract 20 kW but your maxímetro only ever hits 10 kW, you are still billed for 17 kW (85% of 20). You are literally gifting money to the provider.

The clue almost no one looks at

If your billed power is exactly the same every month and matches 85% of your contracted power, you have a 'Power Vampire' in your contract. You are oversized.

How to check it in 60 seconds (Auditor's Checklist)

You don't need a technician to find the truth. Your PDF invoice has the evidence.

What to look for in the PDF

Search for the term 'Maxímetro' or 'Potencia Maxestada'. Compare these values across the different time periods (P1-P6). Usually, one period will be much higher than others.

What to note for comparison

Note down the highest peak of the last 3 months. If that peak is lower than your contracted power, there is a clear opportunity to optimize and save.

If you want certainty: autopsy your bill and decide with numbers

Manual checks are fine, but an automated forensic audit is faster and more precise.

What ahorr.ai detects

Our engine scans the relationship between your peaks and your contracted power. It flags if you are paying the 85% minimum unnecessarily or if you are paying 'Excesos' (penalties) that could be avoided by slightly raising your limit.

What to do with the result

Once you have the report, you can call your provider with the exact numbers. No guessing, no 'maybe'. Just the facts.

Forensic Checklist: Is your Maxímetro working for or against you?

✓Locate the 'Billing Data' section in your PDF invoice.
✓Identify the 'Potencia Facturada' (Billed Power) vs 'Potencia Contratada' (Contracted Power).
✓Check if your billed power is consistently 85% of your contracted power (the minimum billing rule).
✓Look for 'Excesos de potencia' (Power excesses) penalties in the breakdown.
✓Compare the peak recorded by the maxímetro in the last 12 months with your current contract limit.
✓Decide: If peaks are always below 85%, you are overpaying for 'ghost' power.

Maxímetro Billing Logic: The 85-105% Rule

Real Peak vs. Contracted	What you are billed	Impact on your Wallet
Below 85%	85% of Contracted Power	Inefficient: You pay for power you don't use.
Between 85% and 105%	The exact peak recorded	Optimal: You pay exactly for your maximum demand.
Above 105%	Contracted + Penalty (Double the difference)	Critical: High penalties; you need to increase power or manage loads.

This rule is standard for 3.0TD tariffs (SMEs) and some legacy high-power domestic contracts.

The 'Safety Margin' Trap: A Real Case

A family living in a 90m² apartment was being billed under a structure similar to SMEs due to an old contract setup. They had 4.6 kW contracted, believing they needed the 'buffer' to avoid trips. However, their actual peaks never exceeded 2.8 kW. They were paying for capacity they never touched.

Hallazgos

✓4.6 kW contracted vs. real peaks of 2.8 kW.
✓6.99 €/month wasted on an unnecessary 'extra service' fee.
✓Effective cost of 0.23 €/kWh (including taxes) vs. a much lower adjusted alternative.

Not ready to upload?

Create your energy profile manually and we'll tell you what to look for in your specific tariff.

Related guides

Preguntas frecuentes

It is a measuring function within your smart meter that records the highest average power demand in 15-minute intervals. Unlike a 'breaker', it doesn't cut power; it just takes note for billing purposes.

The most common error is having a contracted power much higher than your real peaks. Because of the 85% rule, even if you use 0 kW, you will be billed for 85% of what you contracted.

You can request a power adjustment (bajada de potencia). By aligning your contracted power with your real maxímetro peaks, you reduce the fixed cost of every bill immediately.

Our AI extracts the 'Billed Power' and 'Contracted Power' fields from your PDF. It then simulates the 85-105% logic to see if you are in the 'waste zone' or the 'penalty zone'.

One bill reveals the current state, but a full year (or several bills) allows us to see seasonal peaks (like AC in summer) to ensure you don't lower power too much and hit penalties later.

Transparent and Private

Free, no signup required, and we never store your bills. Just pure data to help you save.

Disclaimers

Informational tool; not financial advice.
We don’t guarantee savings: these are estimates.