Health, cleaning and inverter checks

Helio 2 adds checks that answer "is my system working as well as it should?". This page explains exactly how each one is worked out, what it needs, and where it can be wrong.

System health

Question it answers: was a day good or low for the sunshine it got?

Step	Formula
Specific yield	day's units ÷ panel size (kWh per kWp)
Sunshine	daily solar radiation on flat ground from Open-Meteo, in kWh/m²
Performance	specific yield ÷ sunshine
Your "good day"	the 90th percentile of performance over the last 30 finished days
Day score	performance ÷ good day (100% = as good as your best days)

Status	Meaning
Good	90% or more of a good day
Slightly low	75–90%
Low	under 75%
Too cloudy to judge	under 1.5 kWh/m² of sunshine; low output is expected, so the day isn't scored
No generation	zero units on a day with usable sun
No data	before your WiFi stick started uploading
Not enough history	fewer than 7 scored days so far

Your system is compared with itself, not with a textbook figure, so panel tilt, direction, shading and inverter size are already built in. Sunshine is measured on flat ground, so the percentages are relative, not a formal performance ratio.

Without a location, Helio compares raw yield only and says so: a cloudy day can then look like a problem.

Cleaning advice

Question it answers: is dust costing you output?

1. Take the sunny days (scored, not too cloudy) in the last 7 days since the last wash. A wash is a day with 5 mm of rain or more, or the day you tapped I cleaned them today.
2. Compare their median score with how the panels did on the first sunny days just after the previous wash. If there wasn't a wash in the last 30 days, compare with your best days instead.
3. Advice:

Compared with	Cleaning recommended	Dust may be building	Looking clean
Just after a wash	8% or more below	4–8% below	under 4%
Your best days	12% or more below	7–12% below	under 7%

The thresholds are wider against your best days because normal day-to-day variation would otherwise trigger false alarms. It needs at least 4 sunny days since the last wash.

Limits: dust, new shade (a tree, a water tank) and a failing panel all look the same in this data. Haze and smoke lower output, and the weather model doesn't always capture them fully, so a hazy week can read as a few percent of "dust". The cleaning date is saved on that device only.

Today's estimate

good-day performance × today's forecast sunshine × panel size, shown as a range from the 60th to the 95th percentile of your past performance. It's what a clean system would make if the forecast is right. Forecasts miss passing clouds and haze, so treat it as a guide.

Location

Weather needs your roof's location. Helio picks it in this order:

1. SITE_LAT and SITE_LON, if you set them.
2. The location saved on your ShineMonitor plant. Most installers fill this in, so usually nothing is needed.
3. On the dashboard: Use this device's location (while you're at home) or type the coordinates. Saved on that device only.

Only the coordinates go to Open-Meteo, rounded to 2 decimals (about 1 km), from your own server. Set WEATHER=off to never call it; health then uses raw yield only.

Panel size

Per-kW figures use, in order: SYSTEM_KWP if set, else panels × watts recorded on the datalogger in ShineMonitor, else the plant's nominal power. These can differ: a plant saved as "3.24 kW" may really have 6 × 580 W = 3.48 kWp of panels.

Inverter and grid

Read from the inverter itself through ShineMonitor, every 5 minutes:

• Now: inverter status, output, panel (PV) voltage and current per string, grid voltage and frequency, internal temperatures, grid safety standard.
• Grid check for any day: lowest and highest grid voltage with times, frequency range, and a chart.
• Events:
  • High / low grid voltage: above 110% or below 85% of GRID_VOLTAGE (default 230 V → 253 V and 195.5 V).
  • Grid frequency: more than 1 Hz from GRID_FREQUENCY (default 50 Hz).
  • Output stopped: output at zero for 10 minutes or more while the inverter was producing before and after. If grid voltage was within 3 V of the high limit just before, it's marked as a likely high-voltage trip.

These limits come from IEC 61727, the utility-interface standard many inverters ship with. Installers often widen them, so your inverter may keep running above 253 V; when that happens Helio says so. Field names differ between inverter models; anything your inverter doesn't report is simply not shown.

Alarms and WiFi stick

• Alarms: the inverter's own warnings, errors and faults from the last 180 days, with start and clear times.
• WiFi stick: online or offline, upload interval and firmware.

Export

Export in the top bar downloads CSV files (UTF-8 with BOM, ISO dates) that open directly in Excel, Google Sheets and Numbers.

Daily file columns:

Column	Unit / notes
date, weekday	ISO date in the plant's time zone
energy_kwh	inverter's day counter
specific_yield_kwh_per_kwp	units ÷ panel size
peak_power_kw, peak_time	from the 5-minute curve (ranges up to 93 days)
first_generation, last_generation, generation_span_hours	first and last non-zero sample
solar_irradiation_kwh_m2, rain_mm	Open-Meteo (last 92 days)
performance_vs_best_pct, status	as in System health
grid_voltage_min_v, grid_voltage_max_v, grid_voltage_max_time, grid_frequency_min_hz, grid_frequency_max_hz	inverter readings (ranges up to 31 days)
inverter_temp_max_c, pv_voltage_max_v	inverter readings (up to 31 days)
output_stops, over_voltage_events	counts of the events above
value_min, value_max, currency	all exported → all used at home, at the rates shown on screen
plant_capacity_kwp	panel size used

The monthly file has energy, specific yield, days with generation, average per generating day, best day and value range for each month. Blank cells mean a value isn't available for that day or range.