ahorr.ai · Blog
How to Calculate Your Ideal Contracted Power in 60 Seconds
Respuesta rápida
To calculate your ideal contracted power, sum the wattage of your most-used appliances or check your maximum peak demand on your distributor's website. In Spain, this fixed cost represents a significant portion of the electricity bill, and adjusting it to your actual consumption can lead to immediate savings.
En 30 segundos
- ✓Locate the 'Potencia Contratada' section on your latest bill to see your current kW.
- ✓Identify the 'Potencia Máxima Demandada' (Maximeter) for the last 12 months in the technical details.
- ✓Check if you have different power levels for Peak (Punta) and Off-peak (Valle) periods.
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Transparencia y fuentes
Authorship, methodology and official sources.
Actualizado: 10 de enero de 2026
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Transparencia y fuentes
Authorship, methodology and official sources.
Actualizado: 10 de enero de 2026
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.
Información orientativa (España). Comprueba condiciones con tu comercializadora: precios, peajes, cargos e impuestos pueden variar.
The real problem behind calculating ideal contracted power
Most consumers believe their electricity bill is high because they 'use too much light.' In reality, the fixed term—the power you contract—often represents a massive chunk of the bill that never changes, even if you are on vacation.
What te hace pagar de más
Standard contracts often include 'vampire' services or power levels designed for old, inefficient appliances. If your breaker never trips, you are likely paying for a safety margin you don't need.
What you can actually change
You have the right to change your contracted power. You can even have different power levels for the day and night (P1 and P2) to optimize costs if you use heavy appliances like electric vehicles or storage heaters at night.
Method rápido (without a scientific calculator)
You don't need to be an engineer to find your number. The data is already in your bill; you just need to know where to look.
The data point you need
Look for the 'Potencia Máxima Demandada' section. This is the highest amount of power you actually used simultaneously in the last year. It is the 'smoking gun' of your energy consumption.
How to interpret it
If your contracted power is 5.5 kW but your maximum demand was 3.2 kW, you are wasting 2.3 kW every single month. A safe bet is to set your power at Peak Demand + 0.5 kW to avoid accidental trips.
Checklist before touching anything
Before calling your company to lower your power, run through these forensic checks to ensure you don't end up in the dark.
Señales de riesgo
If your ICP (breaker) trips when you use the oven and washing machine together, you are already at your limit. Lowering it further will cause constant blackouts.
How to avoid surprises
Remember that the distributor charges about €11 for any change. If you lower it too much and need to raise it back, you will pay 'derechos de extensión' which are significantly more expensive.
The decision: Bajar potencia luz
Optimizing your kW contratados is the fastest way to reduce the 'término fijo' of your bill. Once you have the data, the decision becomes a simple matter of arithmetic rather than guesswork.
- →Check your last 12 months of peak usage.
- →Add a 0.5 kW buffer for comfort.
- →Request the change via your provider's app or customer service.
- →Verify the change in your next billing cycle.
Checklist to Calculate Your Ideal Contracted Power
- ✓Locate the 'Potencia Contratada' section on your latest bill to see your current kW.
- ✓Identify the 'Potencia Máxima Demandada' (Maximeter) for the last 12 months in the technical details.
- ✓Check if you have different power levels for Peak (Punta) and Off-peak (Valle) periods.
- ✓Verify if your 'Interruptor de Control de Potencia' (ICP) ever trips (the 'leads' falling).
- ✓Compare your current kW with your highest recorded peak plus a 0.5 kW safety margin.
- ✓Confirm the one-time fee your distributor charges for changing power (approx. €11 per change).
Power Optimization Decision Matrix
| Symptom | Diagnosis | Recommended Action |
|---|---|---|
| Breaker (ICP) never trips even with all appliances on | Power is likely oversized | Calculate peak usage and consider lowering kW |
| Breaker trips occasionally during peak hours | Power is correctly adjusted or slightly tight | Avoid simultaneous use of high-consumption appliances |
| Breaker trips frequently | Power is undersized | Increase power by 0.5 kW increments |
| Fixed term is more than 40% of the total bill | Severe power/tariff imbalance | Immediate forensic audit required |
Lowering power usually costs around €10-11 as a processing fee from the distributor.
The 90m² Flat Trap
A family living in a standard 90m² apartment in Madrid suspected their bills were too high. They had 4.6 kW contracted, a very common default setting. After analyzing their smart meter data via their bill, we found their highest peak in the last year was only 2.8 kW, even during winter months with the heating and oven running.
Hallazgos
- ✓Contracted 4.6 kW vs actual peaks of 2.8 kW
- ✓Paying €6.99/month for an unnecessary 'emergency' maintenance service
- ✓Effective cost of €0.23/kWh due to oversized fixed terms
- ✓Potential annual saving of over €110 by adjusting power and removing 'vampire' services
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We process bills ephemerally. We don't store them, and we never sell your data to third parties.
Disclaimers
- Informational tool; not financial advice.
- We don’t guarantee savings: these are estimates.