Every choice here decides the next one

The inverter's maker, and your supply

Everything downstream hangs off two answers, which is why they come first. The manufacturer decides which batteries, gateways and meters are ever offered — those are compatibility facts about a range, not preferences, and picking a different brand later does not carry your choices across.

Phase is not a preference at all. It is what the supply into the building already is, single or three, and it is a property of the meter cupboard rather than a decision anyone gets to make here. Getting it wrong does not produce a worse system; it produces one that cannot be installed.

What the system is for

A hybrid inverter runs panels and a battery on one machine. Solar only leaves no way to add storage later without changing the inverter — which is the expensive part — and battery only is for a building that already has an array, or is not getting one.

This single answer removes whole chapters below. Choose battery only and there is no roof to specify; choose solar only and the storage chapter disappears.

Series, then power

The series is the family; the power rating is the machine. They are asked separately because the family is the real decision: it fixes which batteries exist, whether a gateway is even offered, and how many battery modules may be stacked. The rating within a family is a sizing question you can revisit.

Every list after this one is filtered by what you pick here.

Modules and how many

Panels are the one part of the system with almost no compatibility constraint, which is why the list barely narrows: a string inverter accepts a wide range of modules.

What the countdoes constrain is the array's total rating against the inverter's input. The sanity of that pairing is the thing worth checking here — rather than the brand, which is mostly a warranty and supply decision.

Gateways and transfer switches

Without a gateway, a grid-tied system shuts down when the grid does — including the battery, however full it is. That surprises people, and it is not a fault: it is the anti-islanding rule that stops an inverter energising a line someone is working on.

A gateway is the transfer switch that makes a backed-up circuit possible. It is offered only where the inverter you chose actually supports one.

Battery, stack and count

The battery list is already filtered to what the chosen inverter can talk to, so this is a shorter decision than it looks.

The two answers after it are the ones that catch people: how many modules the inverter permits in a stack, and whether that stack needs a parallel box to reach the size you want. Both are limits of the inverter you chose two chapters ago, not of the battery.

CTs and export control

A CT clamp or meter is how the system knows what the building is importing and exporting — which is what makes self-consumption, export limiting and any half-sensible monitoring possible.

It is the cheapest part of the specification and the one most often left off, at which point the system runs but cannot tell you, or the network operator, anything about what it did.

The whole system, in one place