The inverter is the heart of a solar PV system. When it stops, the panels on the roof keep catching the sun, but the electricity doesn't reach your home or battery. We repair solar inverters and battery inverters in our service centre in Prague 10. We repair at component level, so it's often enough to replace a fan, a capacitor or a power transistor instead of the whole unit.
How to recognise an inverter fault
| What you see | What it usually means |
|---|---|
| Insulation fault (Isolation fault, ISO, Riso low), the inverter won't start in the morning | Often moisture in the connectors, a damaged cable or panel on the DC side – i.e. not the inverter. If the DC side is fine, the insulation measuring circuit in the inverter is usually faulty. |
| The inverter reduces output at midday, it's hot, the fan is humming or stopped | A clogged heatsink, a faulty fan or dried-out thermal paste. The inverter protects itself against overheating and limits its output. |
| The inverter won't start, the display is dark, or it keeps restarting | A faulty auxiliary power supply, dried-out electrolytic capacitors or the control board. |
| Relay error, the inverter won't connect to the grid | A faulty grid relay or grid measuring circuit. But first rule out high grid voltage – that's a matter for the distribution operator, not the inverter. |
| The inverter is dead after a storm, fuses are blown or there's a burning smell | Surge: damaged varistors, IGBT or MOSFET transistors, their drivers, or the control board. |
| Half output, error on one DC input (MPPT) | A faulty input circuit or a burnt connector. Sometimes it's a faulty panel string, so it's worth having it measured. |
| The display or buttons don't work | A faulty display, its cable or the control board. |
| The app shows offline, the Wi-Fi or LAN dongle doesn't work | A faulty communication module (dongle), communication board or firmware. A restart or a new dongle often helps. |
| The hybrid inverter won't charge or discharge the battery, BMS communication error | Faulty communication with the battery, or the battery converter (DC-DC section) in the inverter. |
What you can check yourself
- Take a photo of the error code on the display or in the app, and of the inverter label with the model and serial number.
- Check the history in the app to see when the fault started and whether it's linked to a storm, frost or rain.
- Check the circuit breakers and fuses in the PV distribution board.
- Never open the inverter cover. There is high voltage inside even after it's switched off.
Safety: the inverter must be removed by an electrician
There's voltage from the panels on the DC side whenever the sun is shining, and on larger installations that means hundreds of volts. The capacitors in the inverter hold their charge for some time after disconnection. Removal and refitting must therefore be done by a qualified electrician, ideally your installer.
- Before removal, switch off the AC breaker, the DC isolator and, on hybrid inverters, the battery as well. Then wait for the time specified by the manufacturer in the manual.
- DC connectors must not be disconnected under load.
- After refitting, your installer recommissions the inverter.
We only work in our service centre. We don't go up on roofs and we don't do PV installations or inspections.
How we repair inverters
- Intake and inspection. We check the inverter outside and inside: signs of overheating, moisture, corrosion and surges.
- Diagnostics. We measure the power supply, the power stage, relays, capacitors and measuring circuits and find the cause of the fault.
- Price in advance. We tell you what's faulty and how much the repair will cost. We don't replace anything without your consent.
- Repair. We replace faulty components: fans, capacitors, relays, varistors, IGBT or MOSFET transistors, connectors, display. If needed, we update the firmware.
- Test. We test the repaired inverter, and only then do we return it.
Brands we repair
| Brand | Typical series | Manufacturer's warranty (usually) |
|---|---|---|
| GoodWe | ET, EH, ES, DNS, DT | 5 years |
| Solax | X1 and X3 Hybrid G4, X3-Ultra, X1 and X3 Fit, X3-MIC | 5 years; for some series 10 years after connecting to Solax Cloud |
| Huawei | SUN2000 | 10 years |
| Fronius | Symo, Primo, Symo GEN24 | 5 years, can be extended |
| SMA | Sunny Boy, Sunny Tripower | 5 years, can be extended |
| Growatt | MIN, MOD, SPH | according to the warranty card, up to 10 years |
| Deye | hybrid SUN-SG04LP3 and others | 5 years, 10 years with extension |
| Victron Energy | MultiPlus-II, Quattro and other battery inverters | 5 years |
| SolarEdge | Home Wave, three-phase SE…K | 12 years (7 in some countries) |
| Others | Sofar, Solinteg, Kostal, Kaco, ABB / Power-One and more | depending on the manufacturer |
Warranty terms vary by series, country and registration. Your warranty card is what counts. Have a different brand? Send us the inverter type and we'll tell you whether we can repair it.
When a repair is worth it
- The inverter is out of the manufacturer's warranty. A repair is usually much cheaper than a new inverter, and you don't have to change settings or deal with battery compatibility.
- Lightning or surge damage. Manufacturers (e.g. GoodWe, Solax, Deye, Growatt, Victron) exclude such damage from warranty. A repair is then usually the fastest way back to generating power.
- Worn parts. Fans and capacitors age, and replacing them often extends the inverter's life by years.
When to make a warranty claim first: if the inverter is under the manufacturer's warranty, contact your installer. Third-party work usually voids the manufacturer's warranty. For small, inexpensive inverters we'll sometimes tell you that buying a new one makes more sense. Even then, diagnostics are free.
How to hand over your inverter
- In person at our shop Rostovská 260/2b, Praha 10 – Vršovice, Mon–Fri 9:00–17:00.
- By parcel within the Czech Republic. Send the inverter via a carrier, usually UPS. We'll tell you the shipping price in advance.
- From Slovakia and abroad. Write to us and we'll arrange transport and the price.
Ideally pack the inverter in its original box, otherwise in a sturdy box with plenty of padding. Include the error code, a photo of the label, a short description of the fault and your contact details. Don't send battery modules without arranging it first – lithium batteries are subject to special shipping rules.
Price and diagnostics
You'll find indicative prices in the price list on this page. We'll give you the exact price including parts after diagnostics, before the repair.
Diagnostics are free if we carry out the repair. They're also free if the repair would cost more than a new inverter. You only pay for them if the repair is worthwhile and you decide to have it done elsewhere.
Warranty
We give a 24-month warranty on every part we replace during a repair.
Have a question about your inverter? Contact us via the contact page or by phone on +420 792 480 835.