Why your potencia contratada is probably wrong

Picture a three-bedroom villa in Jávea. Sea view, modest pool, two split-unit air conditioners, an electric water heater. The owners are Dutch. They use the place for six weeks in summer, two weeks at Christmas, the occasional long weekend. The rest of the year, the house sits empty.

Last year, the electricity bills for the months they were not even in Spain came to €312. About €240 of that paid for capacity they never used — not for any electricity they consumed, but for the right to use a certain amount of power, whether they switched a light on or not.

This is the most expensive misunderstanding in the Spanish electricity market, and it lives quietly on roughly nine out of ten foreign-owned bills on the Costa Blanca North. The fix is free. It takes one phone call. And in 2026 specifically, getting it right matters more than it has in years.

Your bill is two bills, not one

A Spanish electricity bill has two main charges that work in completely different ways. Understanding the split is the unlock for everything that follows.

The first charge is consumo — what you actually used, measured in kilowatt-hours (kWh). If you ran the AC for forty hours, you pay for forty hours of AC. If the house is empty, this number is close to zero. Logical, intuitive, the way most people assume electricity works everywhere.

The second charge is potencia contratada — the maximum amount of power your home is allowed to draw at any single moment, measured in kilowatts (kW). You pay for this capacity by the day, every day, regardless of whether you use one watt or hit the ceiling. It is roughly 40% of the typical Spanish household bill. On a holiday home that sits empty for eight months of the year, it can easily be 90% of the bill.

The standardised potencia tiers available to Spanish homes are 2.3, 3.3, 4.6, 5.75, 6.9, 8.05, 9.2 and 10 kW. Almost every Costa Blanca property sits somewhere between 4.6 and 9.2.

Why this is a 2026 problem, not a generic problem

The fixed-versus-variable split has always been a quirk of the Spanish system. What changed this year is the relative size of the two halves.

In January 2026, electricity network tolls and regulated system charges were updated, adding around 4.1% to the fixed-charge side of every bill. The 'reinforced shield' mode the grid has been operating in since the April 2025 Iberian blackout is keeping additional power plants online to stabilise voltage — and the cost of that, estimated at over €500 million, is filtering into the fixed portion of household bills as well.

Meanwhile, the wholesale electricity price — the engine behind the variable kWh charge — has softened. The January 2026 wholesale average sat at €71.17/MWh, and futures markets are trading 2026 averages well below 2025 levels thanks to record renewable generation. The Ministry for Ecological Transition is forecasting that the typical regulated-tariff household will see final bills drop by about 4.66% across the year, despite the fixed side going up.

The diagnostic: what is your potencia right now?

Pull out any recent electricity bill. Somewhere on it, usually in the contract details box near the top or in a 'datos del contrato' section, there is a line that says something like Potencia contratada: 5,75 kW. That number is the diameter of your pipe.

Now compare it against what your property actually needs. The honest rule of thumb for Costa Blanca North properties looks like this:

If your contracted potencia is one or two tiers above what the table suggests, you are paying the inheritance tax of whoever owned the property before you. The capacity setting almost never gets revisited at sale. New owners sign with the same supplier, same contract, same potencia — and quietly absorb the overcharge for years.

The summer trap (and why winter is a liar)

Here is the catch that traps people who try to fix this themselves. Potencia is sized for your peak simultaneous load, not your average usage. In a Costa Blanca winter, peak load is small — maybe an oven, a kettle, a couple of LED lights. A new owner moves in during October, decides 4.6 kW seems fine, calls the supplier, drops down. Six months pass with no problem.

Then July arrives. Two AC units come on. The pool pump kicks in for its six daily hours. Someone fires up the induction hob for paella, the dishwasher is already running, and the breaker trips. Lights out, fridge off, holiday ruined for an hour while everyone hunts for the fuse box.

The mistake was not the potencia drop itself. The mistake was sizing for winter peaks instead of summer peaks. On the Costa Blanca, the summer peak is the only peak that matters, because that is when you have AC plus pool plus more occupants plus visitors using more appliances at the same time.

This is also why you can't trust gut feel for the fix. The number you actually need is your maximum simultaneous demand recorded in the past twelve months, which your smart meter has been quietly logging the whole time. On Spanish bills it appears as max_demand_p1 (peak hours) and max_demand_p2 (off-peak hours). It is the single most useful number on the page, and it is also the one almost nobody knows how to find.

The maths: what this saves on a Jávea villa

Let's run the Jávea villa from the opening through real 2026 numbers. Assumptions: 3-bed villa, two AC split units, electric water heater, no pool. Currently contracted at 6.9 kW — the previous Spanish owner had electric underfloor heating and needed it; the new Dutch owners do not. Realistic actual peak demand: around 4.0 kW in August.

At 2026 regulated rates of roughly €0.13 per kW per day for the fixed term de potencia, the standing charge math looks like this:

Add the 5.1% electricity tax and 10% VAT that ride on top, and the real annual saving lands at around €125–€130 a year — call it €240 over two years, since potencia changes only really get reviewed when something forces the question.

Crucially, this saving applies whether the house is occupied or not. Months when nobody flies down, when the Wi-Fi router is the only thing drawing power, the saving is the same as in August. There is no other line on a Spanish electricity bill where a single one-time action gives you a guaranteed annual return on an empty house.

For a villa in the larger 8.05 → 5.75 kW band — common in 4-bed properties without pools — the annual saving lands closer to €170. For a small apartment dropping from 5.75 to 3.3 kW, it is closer to €280, because the relative gap is bigger.

Solar changes the calculation, but not the way you'd think

If your villa has solar panels installed, your instinct might be that potencia matters less because you generate your own power. The opposite is true.

Solar reduces your consumo — the variable kWh you pull from the grid in daylight hours. It does almost nothing to your potencia charge, because the grid still has to stand ready to deliver your full contracted capacity at 8pm in February when the panels are dark and the AC is on. Worse: solar households often have the highest potencia settings, because the original installer specified for worst-case grid draw.

If you have solar and your potencia is at 6.9 kW or above, recheck. The economic case for right-sizing is stronger for solar households than for anyone else, because the fixed charge is now a larger proportion of the bill that is actually pulled from the grid.

How to actually change it

Three things matter:

1. Call your comercializadora — the company that sends you the bill (Iberdrola, Endesa, Naturgy, Holaluz, Frank, whoever). Not the distribuidora, which owns the wires. People mix this up constantly because the distributor's name appears on the bill too. The change is a commercial arrangement; the distributor only implements it.
2. Reducing potencia is free. There is no fee, no electrician visit, no paperwork beyond confirming the new tier. The change takes one to two billing cycles to appear, typically within a month. Increasing potencia later, if you got it wrong, costs a one-off fee of roughly €15–€20 plus possibly an electrician check on your installation — which is why getting it right the first time is worth the ten minutes of analysis upfront.
3. Do this before May, not in August when the breaker is already tripping. The change takes a billing cycle to land. If you wait until your AC is overloading the system, you'll either be stuck in the wrong tier through summer or you'll panic-overshoot to the next size up and lose the saving entirely.

The shortcut

If reading your own bill, finding your CUPS, identifying your max_demand_p2, comparing against tier tables and modelling next summer's peak load sounds like a lot of unpaid homework — that is exactly what HolaSwitch is built to do.

Upload your most recent bill and we'll tell you, in plain language, whether your potencia is mis-sized — and if it is, the exact tier to drop to and the annual saving in euros.

The bill upload takes less than a minute. The fix it points to takes less than a phone call. And on a Costa Blanca holiday home, both together are worth more in 2026 than any other single thing you can do to your electricity contract.