In short: single-phase is allowed up to about 15 kW in Spain — ample for almost any home
Whether your solar system runs single-phase (monofásico, 230 V) or three-phase (trifásico, 400 V) depends on your existing connection and on the power your home draws — not on the number of panels. An ordinary home is on single-phase, and in Spain that allows far more than people think: the connection capacity can go up to 14.49 kW (63 A), and for solar generation the standard permits single-phase up to 15 kW. A popular contract is 5.75 kW (25 A), but that’s your chosen capacity — not a ceiling. Only well above what most homes need, around 15 kW, does three-phase become compulsory. Importantly, that limit is about your grid connection, not your inverter or your battery — and that’s exactly where the confusion arises that sometimes costs people a needlessly expensive installation.
Single-phase or three-phase — what decides it?
Your connection, not your roof. Most homes on the Costa Blanca have a single-phase connection; larger villas sometimes already have three.
- Single-phase (230 V) — the standard for an ordinary home. Your connection capacity (the potencia contratada) can go up to 14.49 kW (63 A); many households choose far less (5.75 kW is a common contract), but that’s a choice, not a limit.
- Three-phase (400 V) — for homes that draw a lot of power at once: several air-conditioning units, a pool, perhaps a heat pump. Three-phase spreads the load across three conductors and handles a great deal more.
So the number of panels doesn’t decide this directly — your connection and your peak demand do.
How many kW can single-phase take?
More than most people think. Connection capacity (consumption) can go up to 14.49 kW single-phase (63 A × 230 V), and for solar generation the Spanish standard permits single-phase up to 15 kW. The often-quoted 5.75 kW is not the ceiling but one of the standard contract steps (potencias normalizadas): 5.75 kW is simply 25 A × 230 V, and those steps run from 3.45 kW up to 14.49 kW (63 A). You pick the step that matches your consumption — because you pay a fixed amount every month per contracted kW (the término de potencia), whether you use that power or not, so you take no more than you need. What each step up to 63 A roughly costs, and why you pay for it, is in Potencia contratada in Spain. That contract says nothing about how much you may generate on single-phase.
Watch the distinction most people miss:
- Your connection (consumption) — how much you may draw from the grid: up to 14.49 kW on single-phase.
- Your inverter (generation) — how much your panels and battery deliver: up to about 15 kW on single-phase, since the standard began allowing it in recent years.
The 5.75 kW you often hear is a common electricity contract — not the limit of what single-phase allows. That’s precisely where most people go wrong.
Work out your system in the price estimate, free and without obligation
So can a 6, 8 or 10 kW inverter run on single-phase?
Yes, quite happily. An inverter doesn’t have to stay below your chosen contract capacity: you naturally generate more than you’re using at that moment, and the surplus goes to your battery or the grid. On single-phase a solar inverter may go up to around 15 kW — so 6, 8 or 10 kW is no problem at all. Only above roughly 15 kW is three-phase compulsory anyway.
Why, then, do you often hear you’ll “soon” need three-phase? Because a home that consistently draws that much power usually already has, or takes, a three-phase connection — but that’s a decision based on your total consumption, not a hard limit on your inverter. The exact limits differ by grid operator (i-DE, Iberdrola), so we always check that for your connection before committing to anything.
Note: this applies to a grid-tied system
The limits above apply to solar panels connected to the grid (autoconsumo). An off-grid system stands apart from the grid, and different rules apply there — the maximum power is then set by your installation, not by a grid connection. What that involves is in Going off-grid: what’s involved.
What the phase does not decide: which battery you get
Whether you have one phase or three says nothing about the type of home battery. That’s a separate choice — low voltage or high voltage — which depends on your inverter and your power, not on the phase. We explain that difference in Low-voltage or high-voltage home battery.
What we do for you
We look at your existing connection, work out whether single- or three-phase suits your consumption and your plans, choose the right inverter to match, and arrange the legalisation with Industria. So you can be sure your system is right — technically and to the Spanish standard.
This is one of those points where a second opinion is genuinely worth having, because being told you “need” three-phase is an expensive thing to accept on trust. If another installer has told you that, send us their reasoning and we’ll tell you honestly whether we agree — even if the answer is that they’re right.
Request your free, no-obligation quote — free and no obligation. We’ll work out your situation precisely and put it in writing, so you can compare it against anything else you’ve been quoted.
