Solar Inverters

What the inverter does

Panels produce direct current at a voltage that rises and falls with light and temperature. Your house runs on 230V alternating current, and the grid will only accept electricity that matches its voltage, frequency and phase closely. The inverter does that conversion and that matching, and it disconnects automatically if the grid supply disappears.

It is also the part of the system that thinks. Everything else in a solar installation is passive.

How MPPT works

At any instant an array has one operating point where the product of voltage and current is at its maximum. Draw at a lower voltage and current is high but voltage is wasted; draw at a higher voltage and current collapses. That peak moves continuously — with cloud, with time of day, with panel temperature.

A Maximum Power Point Tracker sweeps the operating voltage and settles on the peak, then keeps re-checking. This is why an inverter’s number of independent MPPT inputs matters more than most specification sheets suggest.

Everything wired to one tracker is held at the same operating voltage. If a south slope and an east slope share a tracker, the tracker finds one compromise voltage, and both arrays run away from their own optimum for most of the day. Split them across two trackers and each finds its own peak. The same logic applies to any group of panels behaving differently from its neighbours — including a shaded group.

The four architectures, compared honestly

String inverter

All panels wired in series into one or more strings, one central box doing the conversion. The lowest cost per watt, the fewest components, the simplest fault-finding, and one unit to replace in fifteen years. On an unshaded roof of one or two orientations, this is usually the right answer and the best value. Its weakness is that a series string is limited by its weakest panel, and it is a single point of failure.

Hybrid inverter

A string inverter with battery management built in. Manages array, battery and house demand in one unit rather than two. The sensible choice when a battery is being fitted now, or is genuinely likely later. It costs more than a plain string inverter, so it is not the right answer for someone who will never add storage.

Microinverters

One small inverter per panel, mounted on the roof. Each panel converts independently, so shading on one affects only that one, and there is no high-voltage DC on the roof. They cost considerably more per watt and put electronics under the array where reaching a failed unit means scaffolding. They earn that cost on genuinely difficult roofs: heavy or complex shading, several small arrays at different orientations, awkward geometry.

String inverter with power optimisers

A middle position. Each panel gets a small DC-DC device that lets it operate independently within the string, while conversion stays in one accessible box. Recovers most of what shading takes, costs less than microinverters, but still adds a device per panel on the roof.

Suitability

The honest summary: unshaded, one or two orientations, no battery planned — string inverter. Battery now or likely — hybrid. Partial shading you cannot design out — optimisers. Severe shading, fragmented arrays, or a preference for no DC on the roof — microinverters. Paying for per-panel electronics on a clear roof buys nothing.

Installation, warranty and cost

Siting drives longevity. Heat shortens electronic life, so a hot loft is a compromise; a garage or a shaded external wall is usually better. All units need clearance for airflow and access for service.

Inverter warranties are shorter than panel warranties and vary widely by product, with extensions often available at purchase. Because the inverter is the component most likely to need replacing, that term is worth reading properly. The specific length, the conditions attached, and the price of any extension are stated on the datasheet and in your written quotation.