Contracted Power Calculator

How to use this calculator

1. Pick your country. Spain and Italy bill in kW, France and Portugal in kVA, Czechia by the rating of your main breaker in amps — the tool switches to the right ladder automatically.
2. Select the power level you contract today (it is printed on your bill).
3. Enter your largest simultaneous load: the total of the appliances that could realistically run at the same instant.
4. For Czech breaker sizing, choose whether that load is on a single-phase 230 V or three-phase 400 V supply; the amps are very different.
5. Click Check my contracted power for the level you actually need, the annual saving, and the payback on the change fee.

Why so many households overpay

Contracted power is a fixed charge. It is billed per kW (or kVA, or amp) per year, and it does not shrink because you were on holiday or because you never come close to the limit. Yet the level is usually chosen once — by a builder, a previous tenant, or a supplier with no incentive to talk you down — and then never revisited.

In Spain, industry estimates suggest roughly 60% of households contract more power than they need, at a cost of tens of euros a year for nothing. In Portugal the penalty is worse than a simple fee, because contracted power interacts with VAT (see below). In Italy the opposite problem is now common: the standard 3 kW supply cannot cope with an induction hob plus an oven plus a heat pump, and the meter trips.

The answer in both directions is the same: work out the largest load that will genuinely run at once, add a margin, and contract exactly that.

Typical appliance loads

The point is simultaneity. The oven, hob, kettle and dryer all have high ratings, but the probability that all four run in the same minute is low in most households — and the tumble dryer can simply wait. Contract for the realistic worst case, not the theoretical one.

The Portuguese trap worth knowing about

Portugal has a rule that costs people real money quietly. VAT on electricity is 6% on the first 200 kWh per 30 days — but only if your contracted power is 6.9 kVA or less. Contract 10.35 kVA and you pay 23% on every single kilowatt-hour, for ever.

So in Portugal, dropping from 10.35 to 6.9 kVA does two things at once: it cuts the fixed power charge, and it restores the reduced VAT rate. The calculator flags this when it applies. Most Portuguese households on 10.35 kVA never needed it in the first place.

Frequently asked questions

What is contracted power?

The maximum power your supply is allowed to draw, agreed in your contract and billed as a fixed charge. Exceed it and the meter trips. Contract too much and you pay for headroom you never use.

How much can I save by lowering it?

It depends on the country's rate, but a single step down is typically worth 30–60 EUR a year in Spain, roughly 35 EUR per 1.5 kW step in Italy, and around 47 EUR for a 9→6 kVA move in France. The change fee is usually small, so it often pays for itself within months.

What happens if I contract too little?

The main breaker trips when you exceed the limit — nothing dangerous, but you have to reset it. If it trips more than very occasionally, go back up a step. That is what the safety margin in this calculator is for.

How do I find my current contracted power?

It is printed on your bill (potencia contratada, potenza impegnata, potência contratada, puissance souscrite) and it is also stamped on your main breaker.

Does an induction hob mean I need more power?

Often yes. A full-size induction hob can draw 7 kW at maximum, though most have a power-management setting that caps the total. In Italy this is the single most common reason households have to move from 3 kW to 4.5 or 6 kW.

Why does Czechia bill in amps instead of kW?

Because the charge is tied to the rating of your main breaker (jistič). The calculator converts your kW load to amps using either single-phase 230 V or three-phase 400 V, so you can compare rungs on the same ladder.