Inverter not turning on
No lights. No display. No response. A completely dead inverter has several possible causes — and the most common ones don't require an engineer. Before assuming hardware failure, work through the power supply checks below.
Note: it is completely normal for inverters to be dark at night — check this during daylight hours only.
If AC supply, DC isolator, and MCBs are all correct but the inverter is still dead, it needs an engineer assessment. Hardware failure diagnosis and repair is usually needed.
Book a Remote Diagnostic — from £75 → Solar system repairSafety: do not open the inverter enclosure. Internal components include live high-voltage DC even when the AC supply is isolated. See our shutdown guide for safe isolation procedures.
Checking at night? Grid-tied solar inverters shut down completely at night — no lights, no display. This is completely normal. Wait until there is at least some daylight (even overcast) before concluding the inverter has a fault. Many early-morning calls turn out to be owners checking at 6am before sunrise.
Why an inverter won't start
Starting with the simplest and most common causes.
Most common cause. The AC solar isolator has been switched to OFF — after a maintenance visit, a power cut, or accidentally. Turn it back on and wait 3 minutes.
The solar circuit breaker in the consumer unit has tripped. Look for a breaker in the mid or down position. Reset once — if it trips again, call an electrician.
On some inverter models the control electronics are powered by the DC string. If the DC isolator is off, the inverter has no power at all, even if the AC supply is present.
Grid-tied inverters require the grid to start. During a power cut the inverter will not operate. It will restart automatically when the grid supply returns.
A lightning proximity event or grid switching transient has damaged internal components. The inverter was working, then a storm or grid event occurred, and it has been dead since. Requires engineer diagnosis.
The inverter itself has failed — capacitor degradation, failed power supply board, or IGBT failure. More common on inverters over 8–10 years old. Requires component-level diagnosis.
Power supply checks — do these first
Do these checks during daylight hours only.
Find the AC solar isolator — usually a red rotary switch mounted near the consumer unit or solar generation meter. Check it is in the ON (I) position. If it is in the OFF (O) position, turn it on. Wait 2–3 minutes for the inverter to initialise and begin startup checks.
Open the consumer unit and look for any MCB in the tripped position (mid or down) labelled Solar, PV, or Inverter. Also check the main RCD or RCBO. Reset any tripped breaker once. If it holds, wait for the inverter to start. If it trips again immediately, leave it and call an electrician.
Locate the DC isolator on or near the inverter. It should be in the ON position. If it is OFF, turn it on. On some inverter models this is the primary power source for the control electronics.
Check that other appliances in the house have power. If the grid is down, the inverter will remain dark until it returns. Most inverters wait 60–90 seconds after grid restoration before attempting reconnection — this is a G98/G99 requirement.
If the AC supply is present, the DC isolator is on, the MCBs are healthy, and there is no power cut — but the inverter is still completely dark — the inverter itself has likely failed. This requires component-level diagnosis and cannot be self-resolved. A remote diagnostic session will confirm the situation before an engineer visit is arranged.
Brand-specific startup notes
Inverter startup requirements differ by manufacturer. Use the note for your brand before working through a full fault investigation.
GivEnergy AIO and Gen2 hybrid inverters require both AC isolation (consumer unit breaker) and DC isolation (rooftop DC switch) to be live before the unit will boot. A blank display with power present usually means DC voltage is not reaching the inverter — check the DC switch and any inline fusing. See the GivEnergy hub for detailed startup checks.
Growatt SPH and MIN series inverters require a complete L/N/E AC connection before the unit will start — a missing Neutral or an open AC output breaker prevents boot entirely. If the display stays blank, verify the AC output terminal block connections at the inverter before investigating further.
Sunsynk inverters include an internal AC output circuit breaker accessible via a small hatch on the unit. This breaker occasionally trips on surge events and is easy to miss. If the inverter receives DC power but does not boot, check and reset the internal breaker before investigating further.
Frequently asked questions
A completely dark inverter means it has no power. Check: the AC isolation switch, any tripped MCBs in the consumer unit, the DC isolator, and whether the house has grid power. These are the four most common causes and all are fixable without an engineer.
Yes — grid-tied inverters shut down completely at night. A dark inverter at 11pm is not a fault. Check it during daylight hours, ideally when the sky is at least partly clear. Some inverters take 15–20 minutes after sunrise to start generating.
Sudden death is often caused by: a power surge from lightning or a grid event; an internal fuse blowing due to a wiring fault; or the AC supply being interrupted (tripped MCB, switched isolator). Check the consumer unit and isolators first. If a storm occurred at the same time, surge damage to the inverter electronics is possible.
Most inverters are rated 10–15 years. String inverters commonly develop faults between years 8 and 12 due to capacitor degradation. If your inverter is over 10 years old and has failed, replacement may be more cost-effective than repair depending on the fault type — a diagnostic will advise.
Inverter confirmed dead — what next?
A remote session reviews whatever portal data is available and confirms the situation before recommending the right on-site service. For a non-responsive inverter, an emergency repair visit may be appropriate.