Five Things to Know About 'Always On'

Always On can be a confusing and controversial “measurement” for some users. But it serves a real and important purpose for users who want to accurately account for their energy usage.

  • Always On is Real - Many devices have an Always On component, that the traditional Sense detection, based on on/off transitions, can never see. For some electronic devices like routers, modems and switches, virtually all their usage is Always On. Most appliances consume both via Always On usage, which powers their controller, and via dynamic usage, when the appliance is actually in operation. Always On on usage typically adds up to a substantial portion of a home’s usage, and doesn’t register in the Sense AI-based detection.

  • Always On is a Broadly Used Concept - Chip designers and electronics designers have been using Always On for years to build power-efficient chips and systems. Chip designers break up low-power chips into separately controllable “voltage and clock frequency islands” that can be turned on and off, put to sleep, and sometimes made to run slower or faster, at will, to keep power usage under control. All the power control smarts and the connections to the outside world that guide the power control are designated “Always On” so they together can manage power usage. For instance, the part of an iPhone processor chip that listens for Siri commands has to be Always On, while many other parts of the processor chip can sleep part of the time.

  • The Always On calculation for your home is useful - In most cases, the Sense calculation gives you a pretty good idea of how much Always On power is being used across all the devices in your home. Because Sense AI detection can’t see Always On usage at the device level, a top level view is very important. And reducing Always on power takes a very different set of strategies and typically targets very different devices than Sense AI detects.

  • The Always On calculation for devices on smart plugs is useful - Sense AI Detection doesn’t show Always On for devices, but smart plugs do, and Sense does a similar calculation for Always On for devices on smart plugs. With smart plug Always On information, one can whittle down the amount of unknown Always on usage contributing to the house level Always On.

  • The Always On calculation is useful, but not infallible - there are few cases where Always On won’t be right. Sometimes Always On can be too large and in one case too small.

    • Overlapping Devices - If a home has two devices, D0 and D1, that are frequently on, and one is almost always on when the other is turned off 24 hours a day, the two devices can hide the lowest points of usage in your home, making the Always On (AO) appear far larger than it really is.

    • A Single Device riding the “hairy edge”. Another user pointed out the usage pattern of one device of theirs that was just the right shape to mess with the smart plug Always On calculation. The short drops in heat pump energy usage when the heat pump stopped, then entered a defrost cycle, then ramped up again were just the right on/off size to cause big changes in the Always On calculation right around the spikes in this screenshot. And a single device pattern that causes fast changes in the smart plug Always On is likely to do the same with top-level Always On

  • Many devices with significant Always On on smart plugs - If you have many devices on smart plugs, your Always On won’t be wrong, but your Other might be artificially small. This is because the Always On is likely double counted by both the smart plug, and in the top-level Always On calculation.

  • Data dropouts - If your usage data sometimes gets dropped (either Total Usage or smart plug usage), that drop shows as a zero for the Always On calculation. If the drop is long enough, your Always On calculation will get pulled down by the zeros, eventually becoming zero if the drop last for long enough. Fortunately data drops are far less common than they used to be.