boyscout wrote:...leaving my machine on from early morning to late evening used less electricity than turning it off and on four or more times per day.

Discussions of the Law of Thermodynamics aside for a moment, four or more on/off cycles per day is a lot. I typically have the espresso machine on for a couple hours in the morning during the week; on the weekend, its working hours are extended into the mid-afternoon. For my usage pattern, turning it on/off once per day is not burdensome. If I simply must have a late night espresso, the Elektra Microcasa a Leva or mypressi TWIST are ready in short order.

Then in your case Dan, all else being equal, my testing says that you'd save money on electricity by turning your machine on and off. A savings balanced against some unknown additional cost for extra thermal stresses on your machine, so you may or may not come out ahead.

I have my office in my home, often here all day, and drinking more coffee than I should... 3-5 doubles per day. My wife hits it up for tea water 3-4 times too - therefore no longer using a kettle, which I did not include in calculations - but her use is often not at the same time as mine. The Kill-A-Watt showed a very clear winner in leaving it on in our situation.

There are certainly a lot of variables here. If you are going to use a machine for multiple sessions throughout the day, AND WILL BE IN ATTENDANCE, then it probably does make sense to leave it on. My VBM is happiest when allowed to warm up for an hour before use. Three sessions a day would mean three hours warm up time per day (or nearly that much).

My comments were meant to dissuade anyone from thinking that such machines should always be left on, 24/7. As a firefighter I was a burn-building, firegrounds instructor, and I had fought a few actual structure fires related to electrical appliances.. exciting and fun for me- not so much for the homeowner. And while cafeIKE was kind enough to PM me about the likelihood of such an event (prompting me to turn off PM'ing for this website), I still personally prefer, and recommend to others, turning off such devices when not at home.

sweaner wrote:Ian, what about turning it on at 6am, off at 9am, then on again at 5pm, then off at 11pm? Can you graph this?

No need to graph.
On at 6 and off at 11 uses 8.04 + 16 * 1.6 = 33.64 vs 8.04 + 2 * 1.6 + 8.04 +5 * 1.6 = 27.28 heat units.
About 20% cheaper with the long off period.

I'm sorry, the break even point is the deadband of the pstat, and not a second longer. In that zone, turning the machine off makes no difference. Once the pstat calls for heat, the machine's temperature delta to the environment is lower than it was at the top of the cycle. Therefore, at the bottom of the cycle its cool down rate is a little slower, and its heat up rate a little faster. As the machine cools, its cool down rate decreases, and its heat up rate increases, and it uses less energy in making the round trip.

Turning off the machine for short intervals artificially increases the dead band on the pstat, while keeping the top temperature the same. So the round trip will take less power. No ifs ands or buts.

But as I say, it's pointless to argue with people who are so vain that they can't even admit to being wrong about basic thermodynamics I do however take bets No limit; since my neighborhood Chicago Democrat bookie loves those born every minute.

Turning your machine off for very long idle periods like overnight or while you're away at work (8 hours or more) is a no-brainer in terms of electricity costs—it's cheaper to turn it off. But these machines cost all of what, $5/month to run 24/7? That's the kind of savings that can be chewed up easily by parts that fail from being heated and cooled repeatedly.

For more background on the topics covered in this thread, there's:
Electricity Usage Monitor
Leave it on, or turn it off?
Is it really safe to leave a HX on 24/7? [CG]

There are a host of other links not far in on that last link. People aren't kidding when they say this topic's been beaten to death, and none of the data that's accumulated (at least what I've seen) gets to the crux of the issue, which really is how much more likely your 'sensitive,' 'expensive' components are to fail running constantly hot vs. getting hot and cold with a repeated on/off cycle. I don't see this happening anytime soon in any case, so do whatever the heck you feel like and don't worry about obsessing over the efficiency of your usage pattern, which if you fully optimize it is gonna save you, what, 20 bucks a year or so max, at the possible expense of shortening the life of parts that cost anywhere from $30 (cheap pressurestat) up to several hundred dollars (brain boxes, button panels, etc.) on your machine?

Randy G. wrote:My comments were meant to dissuade anyone from thinking that such machines should always be left on, 24/7. As a firefighter I was a burn-building, firegrounds instructor, and I had fought a few actual structure fires related to electrical appliances ... I still personally prefer, and recommend to others, turning off such devices when not at home.

Do you also advise people to turn off water heaters and refrigerators when not at home? IMO the justification above is based on anecdotal evidence, not hard data: how does one respond to the advice, don't go outside, you might get struck by lightning? I'd wanna know how likely it is to happen, not hear a couple of stories about lightning strike victims. You may be right, but I think you'd need to to put down some numbers to raise this advice to the level of a well-informed opinion. There are intrinsic risks to having electrical service to your home at all, and it seems like (yes, my possibly ill-informed opinion) this is what a good insurance policy is for.

Finally, regarding the 'Chicago Democrats' comment and subsequent comment about office space, not to mention a few other snarky remarks that have been made in this thread, please keep in mind the site's Guidelines for productive online discussion, namely "Be respectful. Treat others as you would have them treat you." There is no need to take jabs at people when you disagree with what they are saying; it's enough for the sake of productive discussion to state your disagreement and your reasoning behind it.

Rather than try to recall my college physics lessons, this evening I measured my Elektra Semiautomatica using the Kill-a-Watt. The cumulative kWh data from a cold start:

1 hour consumed 0.30 kWh
2 hours consumed 0.45 kWh
3 hours consumed 0.60 kWh

Based on the last hour of usage, it consumes around ~0.15 kWh per hour when fully heated, or 3.6 kWh per day (0.15 * 24). If you were so inclined to cycle it four times per day for two hours per cycle, allowing it to cool completely between each cycle, it would consume 1.8 kWh per day (0.45 *4). The additional energy cost of 24/7 operation in this case would be 1.8 kWh (around $0.20 in our area).

These readings are deceptive, making it seem that shutting down for less than an hour doesn't save energy. The machine doesn't cool off completely in an hour, and would use less than 150 watt-hours to start up. This is true of of any shut down interval.

This thread is not about cost, component wear or anything except energy use. The OP started this thread with an impossible contention that his machine does not obey the first law of thermodynamics, and has backed this with falsified or imaginary data. We are making a laughingstock of ourselves even considering it.

Jim, I think Ian is just messing with us. The punchline should be coming soon.