cgfan wrote:When the numbers you provided are corrected for that it moves your steady-state costs even lower, and hence your break-even point even further out...

I linked several previous discussions of the "leave it on, leave it off?" question in my earlier post. A common assertion is that you can save energy by leaving an espresso machine on versus cycling it on/off (e.g., once in the morning, once at lunch, once in the evening). A number of posters in Leaving a Prosumer HX Espresso Machine On DOES NOT SAVE ENERGY debunk this assertion.

Here's what I measured using a Kill-a-Watt last time this question came up:

HB wrote: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).

Jim adds a helpful qualifying comment:

another_jim wrote: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.

One can readily argue the convenience of extended operation, but there isn't a "break even" point in terms of energy usage. If you're not convinced, see the thread above; or better yet, measure yourself.

HB wrote:One can readily argue the convenience of extended operation, but there isn't a "break even" point in terms of energy usage. If you're not convinced, see the thread above; or better yet, measure yourself.

and

HB wrote: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).

OK, let's say that Dan's estimate of the cost of leaving a machine on 24/7 is on the low side, and instead of $0.20 x 30 =$6 for your average month, let's call it $10. And there may be some additional expense in the summer for people who air condition their houses at night, but for some others there will be savings as "waste heat" enters the room and reduces heating expenses. And let's forget about the arguments such as certain parts lasting longer if the machine is not cycled. Let's just focus on the practical aspects.

Electronic components tend to fail on start up; I don't think that this is even a negotiable point. For whatever reason, this is true, at least in my own universe. Many small leaks in espresso machine plumbing will seal themselves as a machine comes up to temperature and pressure. Once sealed, they tend to stay sealed until a machine is cooled down and then reheated; what will happen the next time is anyone's guess.

Pressurestat seals fail on start up also; I'm not talking about failure in the sense that the electrical parts cease working, I'm talking about the situation where the P-stat fails to evacuate the false pressure, and one is left with a recently warmed up machine that appears to be hot but is not really functional due to vacuum breaker failure. This never happens in a heated up machine in steady state.

Having owned commercial espresso machines for more than 15 years, I can say that I cannot recall a single instance where I went to sleep with a functioning heated up machine and awoke to a non-functioning machine. I guess you could have some sort of failure that would cause the boiler safety valve to blow, but that has never happened to me over this time period. Some cheaper home machines may not be as reliable to leave running unattended 24/7, but good commercial machines are.

I have for short periods of time experimented with using machines on a timer. Even over a period of a few months, I experienced, more than once, a vacuum breaker functional failure where my machine which I assumed was hot and functional, was in fact not usable when I wanted to use it, due to "false pressure" in the boiler. I had other failures as well, including minor startup leaks that did not seal.

Does your espresso usage (or the usage of your friends and guests) always follow a predictable pattern? Do you never have a hankering for a shot after dinner?

To me, $10 a month is a pretty minor expense to pay to be able to make a shot whenever the spirit moves me (or someone else requests it), and to be 99.99% sure that I will awaken to a working espresso machine at optimal thermal equilibrium. There are many other ways that I could save $10/month that would make much more sense to me personally.

ken

Ken Fox wrote:Does your espresso usage (or the usage of your friends and guests) always follow a predictable pattern? Do you never have a hankering for a shot after dinner?

Not all espresso machines require hours to reach thermal equilibrium. Most semi-commercial espresso machines are ready in less than 30 minutes. A typical lever espresso machine is ready in around 10 minutes. The Mypressi TWIST is ready in 3 minutes. It isn't uncommon for hardcore espresso aficionados to own "travel kits" (I use the Elektra Microcasa a Leva for long vacations and the Mypressi TWIST for short ones). If you have such a setup, it comes in handy for those hankering for late night espresso.

So Dan, just so I have this straight; you are hosting a dinner party for friends at the Kehn household, and at the end of dinner some guests express an interest in an espresso beverage. You then proceed to excuse yourself, go into the closet to retrieve your Mypressi TWIST, heat up a kettle, and just leave your big beautiful Elektra sitting cold and dejected on the kitchen counter?

ken

If it were just for a few drinks, I'd probably use the Elektra Microcasa a Leva. It's a pleasure to use, they might enjoy watching the novelty of a lever espresso machine in action, and it only takes 12 minutes from power on until first cappuccino complete.

Dan,

May you be an example to us all.

ken
p.s. do you still drive that Hummer?

So after seeing that plamberti reported on both the turn-on power consumption as well as steady-state power consumption to arrive at the (at least to me) unexpected conclusion that argued for an always-on use for his home setup, I decided to also monitor my power-up consumption. Up until now I just assumed that keeping my equipment on a timer to turn it on every morning was unarguably the way to go for my usage pattern, which is mainly for a morning shot of espresso. (While I do fire it up on occasion in the afternoon or evenings, that is far from an everyday occurrence...)

So from a cold start I measured with my "Kill-a-Watt" device the power consumption up until the brew boiler power extinguished for a first time. Here are my results:

Brewtus I initial warm-up: 0.32 kWH (20 minutes warm-up time)

(While I will use the figure above in my calculations, in reality I would need to keep my Brewtus I on for almost double this time in order to thoroughly heat-soak the group head and portafilter...)

Now unfortunately I never measured for a purely steady-state power consumption, but rather measured the total power-consumption of my Brewtus I over a period of 63 days. Since during this time my Brewtus I would have been turned on by my appliance timer at least 63 times, I can at least deduct the presumed power-up consumption for 63 cycles, though in reality there were probably several more non-timer-activated power cycles for the occasional afternoon to evening shot.

(Note that all Wattage measurements are an effective dissipation number given my usage pattern amortized over the entire measurement period of 63 days, rather than just during its on-time...)

Brewtus I total effective dissipation from earlier post: 29 W

63 power-up cycles consumption: 0.32 kWH * 63 = 20.16 kWH
power-up cycles effective dissipation: 20.16 kWH * 1000 W/kW / (63 days * 24 hours/day) = 13 W

Brewtus I effective steady-state dissipation: 29 - 13 W = 16 W

So it seems that with my usage pattern 13/29 = 45% of the power I consumed over the monitoring period went towards initial warm-up. Which means that if all the power I used to warm-up my machine were automagically used instead towards steady-state operation alone, I could have kept the machine on for 13/16 = 81% longer.

Which implies that if my average on-time per power-up cycle over my measurement period was in excess of 24 hours/1.81 = 13.3 hours, then I might as well have kept it on for the full 24 hours. Though I never did measure it, my daily average usage would have been at most, say, 3 hours a day, which is very very far from my estimated break-even point of 13.3 hours. I'm actually even further from my break-even point as this may make it seem, as if I had really run my machine for an average of 13.3 hours per power-on cycle then the initial warm-up dissipation alone would have been a much smaller percentage of the total power dissipated, moving my break-even point even further out.

This is probably stating the obvious, but as I had assumed with my once a day usage pattern, 24 hours operation is far from being justified from a power consumption standpoint. Now what if I had tripled my current usage, but over 3 discrete turn-on times per day, as might a more frequent espresso consumer. (Doing so keeps the percent used towards initial warm-up the same as my earlier measurements...) So my high estimate of 3 hours a day on-time would turn into 9 hours a day, which still is only 9/13.3 = 68% to my break-even point of 13.3 hours. So even if I had setup my espresso machine to turn on 3 separate and discrete times during the day I still cannot justify 24 hours operation based upon power consumption alone.

All respect to those who keep theirs on for the full 24, but for me it just doesn't work out...