Solar inverter data can seem confusing at first, but focusing on a few key readings can give you a clear and useful picture of how your system is performing. Regularly checking these figures helps you recognise normal patterns and fluctuations throughout the day, such as the rise in power output during peak sunlight hours and the drop-off at dusk. This understanding makes it easier to spot unusual changes or potential faults early on. By knowing what to look for, you can describe any issues accurately when seeking help, enabling quicker diagnosis and resolution.
Keeping an eye on your inverter data not only helps maintain optimal energy production but can also prevent minor problems from turning into costly repairs down the line.
Reading the main inverter figures
Current power, shown in kW, tells you how much electricity your solar panels are producing at that moment. It changes constantly with sunlight, cloud cover and shading, so a low reading during a dull afternoon is not automatically a fault.
Daily energy, shown in kWh, is the total amount generated since the start of that day. Lifetime generation is the cumulative total produced by the system since installation, making it useful for long-term records but less useful for diagnosing a sudden problem.
kW shows the system’s output right now.
kWh shows energy generated over a period of time.
Lifetime generation helps compare performance over months and years.
Exported energy may be different from total generation because some electricity is used in the home first.
Try checking the portal at similar times on clear days rather than judging performance from one isolated reading. It can also help to record the date, weather, current power, daily kWh and any warning messages in a simple note or spreadsheet.
Following production across the day and year
On a clear day, solar output usually rises after sunrise, reaches its highest level around late morning or early afternoon, then falls towards sunset. The graph should generally form a broad curve, although passing clouds, shading from trees or chimneys and changes in household demand can create dips.
Seasonal variation is expected. Longer, brighter days in spring and summer usually produce more energy than short winter days, while low sun angles, cloud and shading can reduce winter output considerably. Comparing this week with the same period last year can be more useful than comparing a bright June day with a cloudy December day.
A gradual reduction in output may be linked to seasonal conditions, new shading, soiling or a change in household energy use. A sudden step-change, where production drops sharply from one day onwards and stays lower, deserves closer attention.
Understanding strings and MPPT readings
Solar panels are commonly connected in groups called strings, with the inverter using MPPT channels to manage their output. Portal readings may show voltage and current for each string or MPPT, although the exact display depends on the system and inverter manufacturer.
At a high level, comparable strings facing the same direction should often show broadly similar behaviour in suitable sunlight. Differences can be normal where panels have different orientations, shading patterns or panel counts, so readings should be compared with the system design rather than assumed to be identical.
One string reading zero while the other expected strings are producing can indicate a tripped protection device, a connection issue or a problem affecting that section of panels. Do not remove covers or inspect live equipment yourself. Record the reading, time, weather and any related alarm, then arrange professional advice.
Checking grid voltage and temperature
Grid voltage is the electrical voltage measured by the inverter at the property. In the UK, supply voltage is nominally around 230V, but it can move within permitted limits. If voltage becomes too high, the inverter may reduce its output or disconnect temporarily to protect the installation and the wider network.
An occasional high reading may be affected by local demand, network conditions or the time of day. Persistent high grid voltage, especially when the inverter repeatedly limits output or restarts, should be reported to a qualified solar or electrical professional. Note the voltage shown, the time it occurs and whether nearby appliances or other local generation are operating.
Temperature readings can also explain lower output. Inverters and panels may reduce power when equipment becomes hot, a process commonly called derating. A warm inverter on a sunny day is not necessarily faulty, but repeated derating in mild conditions, blocked ventilation or unusually high temperatures warrants an inspection.
Red flags worth recording
A sudden step-change in daily production rather than a gradual seasonal decline.
One expected string or MPPT reading zero while others remain active.
Repeated inverter restarts, disconnections or unexplained gaps in the portal graph.
Persistent high grid voltage that limits output or triggers warnings.
Temperature-related derating that occurs unusually often or in moderate weather.
Portal data can occasionally be delayed or inaccurate because of internet or monitoring faults, so check the inverter display if it is accessible without opening anything. Take screenshots where possible, including timestamps and fault messages, and avoid resetting the system repeatedly as this can make the pattern harder to assess.
Take a safe, useful approach
Solar inverter equipment can contain hazardous electrical voltages even when the sun is not shining. Stay safety-first: observe the display or app, record the evidence and follow the manufacturer’s normal user instructions, but never open the inverter, disconnect cables or test electrical parts yourself.
For extra context on warning messages, read our guide to inverter warning lights. If unusual readings continue, contact GEO M&E Ltd on 02392388799 to book a diagnostic visit. Clear records of what the numbers are doing can help an engineer identify the cause more efficiently and recommend the right solution.
