Standby

It reads charge, runtime, load and mains voltage straight off the battery over the USB cable you already have plugged in. When the power goes and doesn’t come back, it shuts the machine down cleanly while there’s still battery left to do it in — and stands down by itself if the mains returns mid-count. Your UPS already speaks the standard HID power protocol, so there is no vendor driver, no background service, no Java runtime and no account; it reads the device Windows already found and leaves the inbox battery driver exactly where it sits.

Once a minute, while on mains with a UPS connected, Standby sends one bearer-authenticated JSON POST to <your endpoint>/submeter. Nothing is sent on battery — the shutdown path is never held up by the network, so treat silence during an outage as missing data, not zero. A 200 means stored; anything else is retried a minute later and logged once, and the token is never logged. Set it up from the tray menu: Push load…

{"id":"office-ups",     stable meter id you chose (letters, digits, . _ -)
 "watts":207,           load in watts
 "label":"Office UPS",  display name you chose
 "volts":121.4,         mains voltage at this outlet
 "load_pct":23,         UPS load as % of rated capacity
 "battery_pct":100,     battery charge %
 "runtime_min":23}      estimated minutes remaining — fields the UPS doesn’t report are omitted

For the receiver: watts is everything downstream of this UPS — a subset of any whole-house figure you already have, so subtract it from your baseline rather than adding it on top. Hold a reading forward for a bounded time (Wattle uses 15 minutes) and treat a longer gap as missing.