Iceboxes & Fridges & Freezers are always-Always On overthink

I’ve semi-ranted about this before but it’s still gnawing at the Sense part of my brain.

This topic lives outside of extensive Always On analysis because I see it as a meta-analysis issue and is essentially an argument in response to this:

So, some arguments

  • Most fridges/freezers are never switched off manually once installed unless for maintenance or replacement. Iceboxes, btw, are considered “non-cyclic refrigeration”.

  • Ask somebody without Sense “Is your fridge always on?”, what is their answer?

  • Looking back though 40+ years of fridge energy data, roughly:
    In 1972 the U.S. standard for household fridge energy usage was around 2,000 kWh/year.
    By 2010 that dropped to around 500 kWh/year.
    By 2019 the most efficient fridges use around 300 kWh/year.

  • Beyond that, and more important to this argument, is that refrigeration technology has been refined. Efficient refrigeration now employs better insulation; fan control; physical thermodynamic design (bottom freezers!); and most importantly perhaps inverter-based compressors. The demands of modern hygiene and refrigeration usage also dictate that temperature variation from optimum has been limited. Fridges work better.

  • These improvements have resulted in fridges that tend to actually run for longer (i.e. be “on” for longer periods) but at significantly lower average power. By extrapolation, fridges move (technologically) toward a literal always-on and always-running state. This matches the fundamental physics and technological limitations. Insulation is much more challenging to improve than compressor efficiency and ultimately every fridge gets opened so effective insulation is always much less than perfect. Knowing that there is a constant average energy loss due to less-than-perfect insulation and that sporadic door opening requires rapid re-cooling, compressors are designed to run near-constantly in efficient fridges. This is very noticeable if you upgrade to an inverter-based fridge.

Here’s my fridge (on a Wemo Insight) as an example:

A typical month:

A typical day:

Currently the Fridge lives outside of Always On (AO) and it’s AO component is 2W. This gives me a false sense of what I would consider Always On in my house. If you want to argue that “Well, there’s nothing you can do about it” in terms of “unplugging to save energy” (which is a core concept of what AO is all about) then I would argue “Well, I could unplug it and get a new, more efficient one”. Same goal/result just on a much slower cycle!

My argument(s) boil down to this:

A fridge/freezer is a special device in regard to it’s AO; it’s AO should be calculated as (Actual On consumption)/(Time plugged in)

My fridge, for example, could list something like 304.1kWh/(365*24h) = 34.7W.
Better, Sense would integrate actual usage over its actual detected time.

The initial listing under AO for a fridge is debatable … perhaps in the order of weeks/months after being detected vs. hours/days … but, I would argue, the AO component is not.

Please argue!

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I dont know what to argue.
All I can think of is thinking of a fridge being “always on” from a non sense user. The fact that it’s plugged in.
Would t that be the case with almost every single device in a home? Maybe it’s a heat pump but it’s not cycling, it still draws a limited amount of power for the transformer to control the boards and thermostat.
Even a television, where it’s in standby, waiting and watching for a signal from a remote.
Kind of got away from your theme @ixu

There are distinctly different device types (incomplete list):

  1. Manually switched on/off for use, e.g. a light; a fan
  2. Automatically switched on/off, e.g. a water pump
  3. Devices with standby, e.g. a TV
  4. Offline-capable UPS/backup batteries, e.g PowerWall
  5. Fridges/Freezers

#1 & #2, depending upon the cycle frequency, have the probability of never clocking as AO.

#3 has a somewhat obvious AO component (standby power) that exists regardless of the usage cycle unless it never goes to standby. Easy case.

#4 is by definition never AO though in some cases has a standby function that would register. In many ways (until it needs to charge) it’s a transparent device.

#5 is by design meant to never be switched off (or unplugged) or go into an equivalent of a standby mode other than perhaps considering a defrost cycle as some form of “standby while we defrost”. Not exactly standard standby. The 2W my fridge uses between cycles is not standby … it’s actually pretty much OFF while still being ON and ready to go … my argument is that because the cycle itself is so constant and the fridge is never actually switched off, then depending on how close you look (in time) you can see it as being AO (or not). It’s always AO because you can’t switch it off. If it goes off for more than a “normal” cycle then it’s a problem.

Another way of viewing it is: What would the AO component of a fridge be if Sense’s sample rate was hourly? (Your TV AO in that case would probably stay the same, the “standby” wattage, unless you watch a lot of TV. The fridge AO would jump closer to what I’m suggesting.)

Was it ever OFF?


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my 2c.
We’re moving to a world where almost all grid attached residential devices are composite devices:

  • They have controller electronics that are always on, listening for some kind of external input and/or running their own timers, sensors. Most major appliances, furnaces, etc. have an always on, electronics board. Smaller appliances are gaining them. Only power tools and vacuums seem to still avoid.
  • Once excited, either via internal or external stimulus, they go into corresponding cycles with perhaps a number of different power modes along the way (think washing machine, furnace or dishwasher, or TV set).
  • They can also run concurrent cycles composed of different types of modes (a server)

Schrödingers cat …

Imagine the ultimate fridge with perfect insulation that never gets opened.

It needs initial power to refrigerate but then can be switched off.

As long as it’s never used (opened) it will keep things cool.

Is it a fridge?

OK, I’ll try a different argument:

A modern fridge is a special case unlike any of your examples because it’s doing work (functioning “as a fridge”) all the time even when in an off cycle as long as it’s switched on! Switch it off and it loses ice cream & “energy” (well actually we know it gains energy, but you get the point).

NAS: Its average power is roughly what it will register as its AO as long as it is always-on. Switch it off and it’s no longer available but you don’t have to throw away your data!

Porsche just announced their first EV … 750HP and it will do regenerative brake charging at 270kW. That could be relevant to my arguments. :wink: