Solar inverter guide
Panels make direct current. The house and the grid use alternating current. The inverter is the device that joins those two worlds, and the type you buy decides whether a power cut leaves you in the dark.
What an inverter does
It tracks the array, converts DC to AC, and synchronises that AC to the grid when a grid is present. It also watches voltage, frequency, and fault current. Those protection jobs are why a normal grid-tied inverter switches off in an outage instead of trying to power the lane.
The nameplate is in kilowatts or kilovolt-amperes. That number is not the same as the module kilowatts. The two are chosen together.
Types
String inverter
One inverter serves a string, or a few strings, of modules. Shade on one module can affect its string. It is the usual rooftop arrangement, as against a microinverter under every module.
Grid-tied inverter
Works only with a live grid. Anti-islanding turns it off during a power cut. It does not charge a battery and it does not provide backup.
Hybrid inverter
Manages panels, a battery, and the grid. Backup is limited to the loads on the backup circuit and to the energy in the battery.
Off-grid inverter
Feeds the loads from panels and batteries without a distribution connection. If the battery is empty and the sun is weak, the loads stop.
Selection ideas
MPPT
Maximum power point tracking continuously adjusts voltage and current so the array stays near its best output. More than one MPPT lets different roof faces run independently.
Efficiency
European or weighted efficiency describes conversion across a day better than a single peak number. A 1% difference is real, but it is smaller than the loss from shade or heat.
DC/AC ratio
Module kilowatts divided by inverter kilowatts. A ratio above 1 is common because modules rarely sit at their nameplate together. Too high a ratio clips midday power. The right ratio is a design choice, not a fixed number here.
Protection
Look for DC isolation, AC protection, surge protection, anti-islanding on grid-tied units, and a clear way to shut the system down. Do not defeat a trip.
Safety
Inverter covers stay closed. Capacitors inside can hold a charge after the switch is off. Alarms and error codes are for a qualified person to interpret. Do not bridge a breaker so the inverter 'keeps running'.
Common mistakes
Buying backup that is not there
A grid-tied inverter stops in a power cut. If backup is the goal, the quotation has to say hybrid or off-grid, and it has to name the backup loads.
Matching the inverter to the bill only
The roof voltage, the string length, and the sanctioned load also limit the choice.
Ignoring where it will hang
Heat, dust, and rain shorten life. The manual states clearances and whether the unit may sit outdoors.
Where to read further
Inverter questions
Does a bigger inverter make more energy?
No. Energy comes from the modules and the sun. An oversized inverter does not create watts the roof did not produce.
What DC/AC ratio should I use?
This page does not give one. The designer checks clipping, the inverter's allowed window, and the roof. Ask to see that check.
Can I add a battery to a grid-tied inverter later?
Not usually, unless that inverter was built for it. A later battery often means a hybrid inverter or a separate arrangement, which is a new design.
Related guides
- Solar panel technologyCells, module types, efficiency, heat, degradation, and why DCR matters for the central scheme.
- Solar structure and mountingThe structure holds the modules to the roof. Its size is an engineering result, not a catalogue guess.
- Solar wiring and protectionDirect current from the roof and alternating current in the house are protected differently.
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