How are Always On and Idle calculated?

With the introduction of the smart plug integration and with the recently released Always On Stats feature, many users have asked how exactly we calculate Always On usage and the related, but different, Idle state. In the interest of full transparency, these definitions are pretty technical. You can find more simplified explanations at the link above. Note that these calculations are subject to change.

Always On

Always On is a calculation of the lowest power of each of your mains, added together, where “lowest” refers to the 1% bin of the observed wattage histogram over the previous 24-48 hour period. It is updated every half second, though most users will not see significant real-time changes given the 48 hour lookback window.

Always On component of a smart plug device

This is an estimate of the Always On-ness of a smart plug device based on its power draw over the past 24 hours. It is updated once every few hours based on consumption data. Always On-ness is determined by looking at the distribution of wattage at a high granularity (1 second) and estimating a value corresponding to the 1% bin of its observed wattage histogram. It may or may not align with the state of a device, such as “Idle”, which is determined by a more complex set of algorithms.


An “Idle” state is only calculated when a smart plug device spends a thresholded amount of time (about 15%) significantly higher than the lowest, non-zero wattage cluster. Devices that have a constant wattage do not have an Idle component. Idle exists to prevent on/off notification spam; some devices (like fridges with cycling mullion heaters) turn on and off in a way that doesn’t match what most users think is “on.”

For example, a security camera is an Always On device with no Idle; it always uses the same wattage. A fridge with a cycling mullion heater is a device with no Always On but does have an Idle state, when the heater is cycling. The fridge is “On” when any combination of the compressor, fridge light, icemaker, or defrost element is on. A smart TV might have both an Always On and an Idle state where it consumes a constant wattage regardless of on/off status while also consuming a low Idle wattage in certain situations like a sleep or rest mode.