In short: you pay monthly per contracted kW — so take what you need
In Spain you choose your own potencia contratada (connection capacity), and you pay a fixed amount every month for it — per kW, whether you use that power or not. Reckon on roughly €2.40 per kW per month: contract 5.75 kW (25 A) and you’ll pay around €14 a month; take the single-phase maximum of 14.49 kW (63 A) and it’s about €35. So take what you actually need. And, importantly for solar panels: this fixed rate doesn’t limit your generation — you may feed in up to about 15 kW on single-phase, even on a small contract.
The figures in this article are estimates. They’re based on the level of Iberdrola’s Plan Estable (tariff 2.0TD), excluding 21% IVA, and they vary by supplier and by year — the government adjusts the regulated portions annually. For your exact figure we look at your own contract and grid operator.
What does each step cost, from 15 to 63 A?
On single-phase, connection capacity runs from 15 A (3.45 kW) up to the single-phase maximum of 63 A (14.49 kW). Since 2018 you may contract any capacity up to 15 kW in steps of 0.1 kW — below are the most commonly used (standardised) values and roughly what the fixed capacity charge alone costs per month:
- 15 A · 3.45 kW → ~€8
- 20 A · 4.6 kW → ~€11
- 25 A · 5.75 kW → ~€14
- 30 A · 6.9 kW → ~€17
- 35 A · 8.05 kW → ~€19
- 40 A · 9.2 kW → ~€22
- 45 A · 10.35 kW → ~€25
- 50 A · 11.5 kW → ~€28
- 63 A · 14.49 kW → ~€35
Going from 25 A to 63 A is therefore about €21 more a month (~€250 a year) — on exactly the same connection. This is the capacity charge only; your energy consumption and 21% IVA come on top.
Work out your system in the price estimate, free and without obligation
Why does more capacity cost more — it’s the same connection, isn’t it?
Good question, because the cable doesn’t change. The answer: you aren’t paying for the cable, but for reserved capacity. The fixed capacity charge (término de potencia) is literally the capacity the grid keeps free for you, whether you use it or not.
Contract 63 A, and the grid has to be able to deliver you 14.49 kW at any moment, guaranteed — transformers, cables and the whole network are sized for it. At 25 A you’re only reserving 5.75 kW. Same wire, but a bigger claim on the shared network, so higher fixed costs. Think of a reserved table in a restaurant: a table for eight costs more than a table for two, even if you don’t always fill it — it’s being kept free for you.
“I physically have 63 A already — so why do I have to declare anything?”
Because two things get muddled that are really quite separate:
- Potencia máxima admisible — what your installation can physically and safely handle (your wiring and the official boletín, 63 A for instance).
- Potencia contratada — what you contract, pay for and may draw.
The limiter in your meter cupboard — formerly the ICP switch, now the smart meter — cuts off at your contracted capacity, not at what the cable can take. If you have 63 A wiring but contract 25 A, the meter trips at 5.75 kW: the wire could do more, but you may not without contracting (and paying for) it. Your 63 A installation is therefore only the ceiling of what you could draw; you pay for what you actually reserve. If you genuinely want to be able to pull up to 63 A, you contract 14.49 kW and pay around €35 a month; otherwise the meter keeps you lower.
Important: this doesn’t limit your solar panels
All of this is about drawing from the grid — how much you pull out of it. Your solar panels do the opposite: generating and feeding in, and a different, far more generous limit applies there. On single-phase you may generate up to about 15 kW, even if you’ve only contracted 25 A (5.75 kW). So you usually don’t need to increase your contract in order to fit solar panels — precisely the misunderstanding that sometimes pushes people needlessly towards a more expensive contract or towards three-phase. More on that in Single-phase or three-phase in Spain.
What we do for you
We look at your current contract, your meter cupboard and your consumption, and advise which connection capacity suits you — no more than you need, so you aren’t paying every month for capacity you never use. And we show exactly how your solar system stands apart from it. So you know where every euro on your bill comes from.
One honest note on the numbers, because this is the sort of article where it’s tempting to promise too much: payback on a home system here typically runs 5 to 7 years, or 4 to 6 with the grants where they apply, and surplus you feed back earns around €0.065/kWh. We won’t promise you a zero bill or guarantee a fixed yield — nobody honestly can. What we will do is set up the monitoring on your phone so you can watch the actual figures for yourself.
Request your free, no-obligation quote — free and no obligation. We’ll work through your situation precisely, and you’re welcome to take the numbers away and check them.
Curious how quickly it all pays for itself? That’s in How quickly do solar panels pay for themselves on the Costa Blanca.
