Learn how to spot solar monitoring underperformance, faults and unexpected changes in your solar output.
Solar Panel Monitoring: What the Numbers Mean
Key numbers and what they mean
Current power output (W or kW): This shows how much electricity your solar panels generate right now. On a clear summer day, a 4kWp solar PV system might produce around 3,000–3,800W near midday. On an overcast day, it could produce just 200–600W. Output changes constantly with sunlight, clouds, shading, panel temperature and the sun’s position. Therefore, short-term changes are normal.
Today’s generation (kWh): This shows how much electricity your panels have generated so far today. As a rough guide, a 4kWp south-facing solar system might produce 18–22kWh on a good summer day. In winter, it may generate around 2–6kWh on a typical day. However, location, roof direction, shading and weather can all affect the result.
Annual generation (kWh): This provides one of the best ways to check solar panel performance. Compare your monitoring data with the annual estimate in your original solar quote or commissioning report. Some variation is normal because weather changes each year. However, a persistent shortfall deserves further investigation.
Warning signs to watch for
Zero solar generation on a clear day: Your panels should produce electricity in good sunlight. If the app shows zero, check the inverter status light first. Also check the monitoring connection and any solar inverter fault codes. If the inverter shows an error, contact your installer or a qualified solar engineer.
Much lower generation than last year in similar weather: A large drop can signal a problem. Possible causes include new shading, dirty panels, damage, inverter faults or monitoring issues. However, avoid judging performance from one day alone. Compare several days or weeks instead.
Generation repeatedly stops and starts: Intermittent output can point to grid voltage problems, inverter protection settings or other electrical faults. This can happen in areas with lots of rooftop solar. Therefore, repeated interruptions need investigation rather than being treated as normal.
