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.
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.