Guide · Diagnostics
Solar Monitoring Data Explained
Direct answer
Reading the production graphs in your inverter monitoring app or VRM portal. What a healthy day looks like, what a fault looks like, and what to ignore.
Your solar monitoring app shows you everything the system is doing, if you know what to look for. Most owners check it once when it’s installed and never again. Worth the ten minutes to learn how to read it, because the patterns tell you whether the system is healthy long before any fault code appears.
What a healthy production graph looks like
A clear-sky day on a north-facing array produces a smooth bell curve. Production starts at sunrise, climbs steadily, peaks at solar noon (around 11:30am to 12:30pm depending on your longitude and time of year), then declines smoothly to sunset.
Key features of a healthy curve:
- Smooth, continuous shape: no sharp drops, no spikes
- Symmetrical or near-symmetrical around solar noon. East-west arrays will be flatter, but still smooth.
- Peak production roughly equal to system size: a 6.6 kW system peaking at 4.5–6 kW at midday is normal (panels rarely produce their full nameplate rating because of temperature de-rating)
- Production starts within an hour of sunrise and ends within an hour of sunset
A healthy summer day for a 10 kW system in Hope Island would produce 50–65 kWh. A healthy winter day produces 30–40 kWh. If your numbers are materially lower than this, something’s wrong.
Common patterns that indicate problems
The midday flatline
Your production curve climbs normally, then suddenly flattens at a specific kW value, holds that level through midday, and then declines normally. Cause: clipping. The inverter is producing at its maximum capacity and ignoring the extra solar energy. This happens when an array is oversized for its inverter. Not always a problem, often a deliberate design decision, but worth understanding.
The asymmetric drop
Production climbs normally in the morning, peaks where it should, then drops faster than expected in the afternoon. Cause: shading. Trees, neighbouring buildings, or new construction casting afternoon shadows. Worth a roof inspection.
The sudden cliff
Production was normal yesterday, today it’s zero or near-zero. Cause: a fault that happened overnight or this morning. Check the inverter screen and fault log immediately.
The long slow decline
Comparing this month to the same month last year, production is 10%+ lower. Causes range from soiling (cleaning required) to panel degradation (warranty claim) to a slowly failing string. Worth a Solar Health Check.
The repeated afternoon drop-out
Production looks normal in the morning but drops to zero around 2–3pm every day, then resumes around 4pm. Cause: grid voltage exceeding the inverter’s tolerance band. The inverter is disconnecting to protect itself. Solution is volt-watt response configuration, battery storage, or asking the DNSP to investigate the local feeder voltage.
The morning under-production
Production is fine all day except for the first 1–2 hours after sunrise. Cause: usually shading from a tree or chimney that the original installer didn’t account for. Sometimes string mismatch (panels in different orientations on the same MPPT input). Fixable by reconfiguring or adding optimisers.
What to ignore
Not every dip in the graph is a fault. The following are normal:
- Cloudy days: production drops 30–80% on overcast days. That’s just weather.
- A 2–4% drop year-on-year: panel degradation is normal, typically 0.5%/year, sometimes more in the first year. Anything under 5% per year is within manufacturer specification.
- Lower production in winter: solar irradiance in Queensland is roughly 50–70% in mid-winter compared to mid-summer. Lower sun angle, shorter days.
- Brief production spikes above nameplate: on cool, bright days right after a thunderstorm, panels can briefly produce above their rated output. The inverter will clip if needed; otherwise it’s a free bonus.
Where to find the data
Each inverter brand uses its own portal. None of them are particularly user-friendly. Bookmark the relevant one.
| Brand | Portal | Notes |
|---|---|---|
| Fronius | Solar.web (solarweb.com) | Best fault visibility of the four |
| SMA | Sunny Portal (sunnyportal.com) | Good historical data, slow interface |
| Sungrow | iSolarCloud (app and web) | App is better than web |
| GoodWe | SEMS Portal (semsportal.com) | Basic interface, gets the job done |
| Victron | VRM (vrm.victronenergy.com) | The best monitoring portal of any brand |
The Victron VRM is in a different league. If you have any Victron equipment in the system, you’re probably already using it. If you don’t and you’re considering a battery system upgrade, the monitoring quality alone is worth the price difference.
What good monitoring looks like
If you’re specifying a new system, monitoring quality is something to push for during quoting:
- Real-time data (refreshing every 5–60 seconds, not every 15 minutes)
- Historical data going back at least 2 years with the ability to download CSVs
- Per-string visibility: not just total production, but each MPPT input separately
- Battery state of charge and battery cycle history (if you have storage)
- Grid import and export tracked separately: useful for tariff optimisation and detecting feed-in cap issues
- Alerts via email or app push: not just on the portal, where you’d have to check it
A Home Assistant integration on top of your inverter’s native monitoring layer adds:
- Single dashboard combining solar, battery, grid, and household consumption
- Custom alerts (e.g. “notify me if production drops below 80% of expected”)
- Permanent local data retention (the manufacturer’s cloud may not keep your data forever)
- Integration with other systems: water tanks, pool pumps, EV chargers
Common questions
My monitoring shows zero but my power bill says I’m exporting solar. Which is right? Both. The export meter is what your retailer pays you on, and that’s based on the smart meter reading. Inverter monitoring is separate. If they disagree, the meter wins for billing purposes. The disagreement itself is a sign that the inverter monitoring connection has failed. The system is still producing, but you’ve lost visibility.
How long does monitoring data last on the cloud portal? Depends on the brand. Fronius keeps data indefinitely. Others delete after 2–10 years. If long-term data matters to you, set up a local Home Assistant integration that pulls and stores the data on your own hardware.
Can I check production from outside Australia? Yes. All the major monitoring portals are accessible from anywhere via web or app. If you’ve set up a VPN to your Home Assistant, you also get access to your local dashboard from anywhere.