Zero, missing or stale: three different readings

Ask whether the field is supported

Start with the exact device and field. An inverter may report battery-terminal voltage without reporting individual BMS cells. A controller may report its own load output without measuring the whole property. If the field is not available from that source, an empty tile is not equivalent to zero.

Compare the supported measurement set with what the dashboard expects. Do not invent a replacement value because another tile looks related. Unknown grid import should remain unknown rather than being displayed as no import.

Check freshness before interpreting magnitude

Read the timestamp and connection state. Sunstead’s live aggregation treats connected samples within its freshness window as current; older samples are not interchangeable with live measurements. A browser can remain visible even when collection has stopped.

Use actual timestamps in a support report. “It looked old” is much less useful than “the last sample was 14:32, viewed at 18:10.”

Look at neighboring evidence

Check whether other fields from the same device are updating. If voltage and status are current but one field is absent, investigate field support or parsing. If every field from one device is stale, investigate that device’s communication path.

If all equipment readings are stale across multiple screens, investigate the host or collector before blaming the screen. If one browser is frozen while another is current, begin with that browser’s connection and rendering.

Keep zero out of missing intervals

Substituting zero for a missing power sample can understate energy use or production. Carrying the last value indefinitely can overstate it. Preserve the gap and explain the coverage instead.

Home Assistant’s integral documentation illustrates how sampled power can be converted into an energy estimate. The result depends on the samples and method; a gap is not a measured zero interval.

Use a classification record

• Field name and unit.
• Device identity and interface.
• Visible value or unavailable indicator.
• Last sample time and observation time.
• Other fields from the same source.
• Comparison from another screen.

End with a provisional category: supported fresh zero, unsupported or unavailable field, stale source, or screen-specific issue. It is acceptable to leave the category unresolved when the necessary timestamp or source information is missing.

This small classification prevents large unnecessary changes. You can investigate a missing BMS field without altering battery settings, and investigate a frozen browser without reconnecting equipment that is still reporting correctly.