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A solar inverter takes the direct current from your panels and turns it into the alternating current your lights, appliances and the utility grid actually use. That is the whole job. It does not store energy, it does not make the panels produce more sun, and it cannot run the house during a power cut unless it is a hybrid with a battery. Everything else people argue about — string or micro, hybrid or grid-tied — is a different way of doing this one conversion.

On a sunny midday a home array might be at 400 volts DC or, with microinverters, at about 60 volts DC under each panel. The sockets in the house want roughly 230 volts AC at 50 or 60 hertz, depending on the country. The inverter is the box that crosses that gap, keeps the waveform clean enough for the grid to accept, and stops immediately if the grid disappears.

Last updated: October 2026. The steps below describe a grid-tied string inverter, which is still the most common design. Differences for hybrids and microinverters are marked where they change the story.

The short version of the path

  1. Panels make DC. Light frees electrons in the cells. Current rises and falls with sunshine. Voltage moves the other way with heat: a hot panel produces a lower voltage than the same panel on a cold morning.
  2. The MPPT finds the useful point. There is one combination of voltage and current where that panel, right now, delivers the most power. The tracker hunts for it.
  3. A switching stage chops the DC. Transistors pulse the current thousands of times a second.
  4. Filters turn the pulses into a sine wave at the grid's voltage and frequency.
  5. A relay connects, or refuses to. If the grid is inside its limits, power flows. If the grid is down or out of spec, the inverter opens and stays open.

What the panels are actually handing over

A photovoltaic cell is a one-way electrical source. Connect nothing, and you measure an open-circuit voltage. Short the leads, and you get a short-circuit current with almost no voltage, which means almost no power. Power is voltage times current, so the useful spot sits on the bend of that curve, where neither number has collapsed.

Sunshine pushes the current up and down. Temperature pushes the voltage. A cold, bright morning can put the array voltage higher than a summer noon, which is why the inverter's maximum DC voltage has to be checked against the coldest day at the site, not against the sticker on the panel at 25°C. Exceed that voltage and you are not "making more power." You are outside the rating that keeps the transistors alive.

Shade, a cracked cell, or a string of mismatched panels puts more than one bend in the curve. A single tracker can sit on the wrong bend and leave power behind. That is the entire reason a roof with two directions wants two trackers, and the reason a heavily shaded roof starts a conversation about module-level electronics. It is not a reason to expect any inverter to invent watts the cells did not make.

How maximum power point tracking works

The tracker is a controlled DC-DC stage. It changes the electrical load the panels see, watches the power that results, and steps toward more of it. Dozens of times a second it nudges the voltage and asks whether power went up or down. The method has been standard for years. What you buy is not the existence of a tracker. It is how many independent trackers the inverter has, and how much current each one will accept.

A small home inverter often has two. Each tracker wants its panels matched: same orientation, same shade, same number of modules. Hang an east array and a west array on one tracker and the tracker has to compromise. Hang them on two trackers and each roof face keeps its own bend in the curve. A microinverter takes this to the limit and gives every panel a tracker of its own. The hardware principle is identical. The number of trackers is the product decision, and it is covered in string inverter vs microinverter.

Current is the spec people skip. A modern 550–700 W panel can push a high short-circuit current. If the tracker's maximum input current is below that, the inverter quietly throws the extra away all year. The datasheet line matters more than a claim of "99.9% MPPT efficiency," which only describes how well the tracker sits on the curve, not whether the curve fits the input.

From DC pulses to a grid sine wave

Once the tracker has a stable DC bus, a bridge of transistors connects that bus to the AC terminals in alternating polarity. Left alone, that would be a crude square wave. The transistors are pulsed with a varying duty cycle, pulse-width modulation, so the average of those pulses follows a sine. Inductors and capacitors then smooth the edges. What leaves the inverter is a sine wave locked to the grid.

Locking is the part a battery inverter and a grid inverter do differently. A grid-tied inverter watches the utility voltage and matches its frequency and phase. It is a guest on someone else's waveform. An off-grid inverter has no guest role. It creates the waveform itself, which is why you cannot casually parallel it with the street. A hybrid does both jobs, at different moments: guest while the grid is up, host on the backup terminals when the grid is not. The conversion hardware is the same family. The control rules are not.

Most home inverters today are transformerless. They are lighter and a fraction more efficient than the old transformer designs. They also leak a little current to earth by the nature of the circuit, so they need residual-current monitoring and a proper earth. That is a wiring requirement, not a brand preference. Older transformer-based inverter-chargers, still common off-grid, are heavier and more forgiving of motor surge. You can see the difference on a pallet before you read a word of marketing.

Why it switches off when the grid switches off

If a tree takes the line down, the inverter must stop sending power into that line within a fraction of a second. Otherwise a worker isolating a fault can still find voltage coming from your roof. The inverter watches voltage and frequency. Step outside the window the local grid code defines, and a relay opens. Come back inside the window and stay there for a set delay, and the inverter reconnects. It will not "help" the grid by staying on. Helping, in this case, would be the hazard.

This is also why a house with a normal grid-tied inverter goes dark in a blackout even in full sun. The panels may be producing. The inverter is doing what the law requires. Backup during that blackout needs a battery and a hybrid, or a separate backup inverter, that can open the grid connection and then power an island of circuits on the house side. The physics of DC-to-AC does not change. The permission to keep running does.

The windows are not universal. Germany, Britain, Australia, the Philippines and California each publish their own voltage, frequency and reconnect delay. A unit can be electrically excellent and still be the wrong unit if its certificate names a different grid. "CE" does not answer the question. The national grid code on the certificate does.

Matching inverters, isolators and cable to the DC voltage you are actually building?

Where the energy goes missing

No inverter is 100% efficient, and the peak number on the cover is the best moment, not the year. At very low power, early morning and late afternoon, the control electronics are a large share of what the panels are making, so efficiency drops. In the middle of the day a good string inverter is often around 97 to 98.5%. Weighted figures, such as European efficiency, average this across a realistic mix of power levels. Compare those, or compare nothing. Comparing one brand's peak with another brand's weighted number is how a worse inverter wins a spreadsheet.

Heat is the other loss you can hear. Transistors and magnetics dump the wasted percent as heat. If the heatsink cannot get rid of it, the inverter derates: it deliberately reduces output rather than cook itself. A 10 kW nameplate at 45°C in a sealed closet is not a 10 kW inverter. Fans avoid the derate and annoy anyone whose bedroom shares the wall. Natural convection avoids the noise and needs shade and clearance. The manual's clearance diagram is a performance spec.

At night a grid-tied inverter still draws a little power, usually well under a couple of watts on current models, sometimes more if a hybrid is holding a battery management system awake. Over a year it is a small bill. It is not zero, and it is why the monitoring portal can still see the unit after sunset.

What the display is telling you

A healthy inverter, on a clear day, shows AC power close to what the array should produce after conversion loss. A few checks separate a fault from a dull sky.

  • DC voltage in range, AC power near zero. The inverter is awake but not connecting. Grid voltage or frequency is outside the window, the relay is open, or export has been limited to nothing.
  • Power far below the array on a clear day. A string may be down, a tracker may be clipped by current, or shade has pushed the tracker onto the wrong part of the curve. Module-level monitoring finds this faster. String monitoring only tells you the total.
  • The unit runs, then derates every afternoon. Heat. Look at clearance, direct sun on the cabinet, and whether the fan is actually turning.
  • It trips when a large load starts. More common on hybrids and off-grid inverters. The load surge is above the overload rating. The solar is not the problem.

Where ShineTong fits

ShineTong builds microinverters, the version of this circuit that sits at the panel instead of on the wall, in single, dual and quad units. We do not build the large grid-tied string inverters or the hybrids described above. The DC hardware around either design is the same kind of work: isolators rated for the array voltage, surge protection, connectors and cable.

If you are specifying a roof and you want the conversion at module level, or you want the wall inverter from another brand and the DC parts from one shipment, send the panel model and the destination grid. The voltage and the grid code decide what we can ship. A 60 V microinverter input and a 600 V string input are not interchangeable parts, and we would rather decline the line than put the wrong one in the box.

Specifying the DC side of an inverter?

Tell us the panel model, the inverter type and the country. We reply with options, documents and lead times. No public price lists.

Related reading

Frequently asked questions

What does a solar inverter do?

It converts the direct current from solar panels into alternating current at the voltage and frequency of the local grid, and it disconnects if that grid is absent or out of limits. In a hybrid it can also charge and discharge a battery. It does not store energy by itself, and it does not increase the amount of light the panels receive.

Does a solar inverter work at night?

It does not convert solar power at night, because the panels are not producing. A grid-tied inverter stays in a low-power standby so it can reconnect at sunrise, and that standby draws a small amount from the grid. A hybrid may still supply the house from the battery after dark. The solar conversion itself waits for light.

Why does my inverter shut down during a blackout?

Because it is required to. Anti-islanding protection stops the inverter from energising a dead utility line. A standard grid-tied inverter then has no role until the grid returns. Backup power during the blackout needs a battery and a hybrid or backup inverter that can disconnect from the street and run selected circuits on their own.

What is MPPT on an inverter?

Maximum power point tracking. The inverter constantly adjusts the load on the panels so they operate at the voltage and current that produce the most power under the current sun and temperature. More than one MPPT lets different roof faces or shaded strings run at different voltages. One MPPT shared across mismatched panels compromises.

How efficient is a solar inverter?

A current grid-tied string inverter often reaches about 97 to 98.5% near full power. The figure that describes a year is a weighted efficiency, not the peak. Efficiency is worse early and late in the day, and the inverter will also reduce output if it overheats. A half-percent gap between brands is usually smaller than losses from shade, heat or a mismatched string.

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