Pressure at the pump is not that relevant. What is relevant is the pressure at the point where pressurized water meets the coffee puck. And this pressure very much depends on multiple factors but let's say that the coffee ground level is one of the most important things. If you have a pump pumping water at 15 bars but you have a very coarse ground coffee in your basket, resulting pressure is _not_ going to be 15 bars. Similarly, if you grind the coffee at very fine levels then the resistance of the coffee puck will increase and therefore resulting pressure might very well end up being _more_ than 15 bars.

That said, another thing which plays a big role in the resulting pressure is the design of the brewing head and the design of your basket. Baskets can be either pressurized (they have a single hole through which the coffee will flow) or non-pressurized (they have a lot of small holes through all of which coffee will flow). You can imagine that the resulting pressure will depend on the type of the basket you're using.

Because cheaper appliances will by default use pressurized baskets, they will tweak the pump to some pressure level which they found to work the "best" for their type of machine and that level is exclusively much more than expected 9-10 bars. Nespresso will for the same reasons do the same with the difference that they make one step forward to take over the full control over the puck preparation process through their prepackaged pods.

Doesn't the OPV release any excess pressure above a certain setting?

OPV machines sure but I was referring to appliances in the field. I don't think these are OPV capable?

Even the Gaggia Classic has an OPV, and it's an entry level machine.

Ok, what's the point you're trying to make? In the early beginning I have had DeLonghi and it most certainly didn't have any OPV.

Well you made some statements in your previous comment about pressure which suggested they were generally applied to espresso making. That simply isn't true.

Espresso machines without OPV are really a minority. Even single-boiler entry level machines like the Gaggia Classic or the Rancilio Silva have an OPV.

Parent comment seemed to suggest that (much) higher pressure produces better espresso and my comment had a sole intent, at the expense of simplifying some things, to give some grounds why espresso manufacturers might use higher than 9-10 bar pressure at the pump.

Gaggia Classic is a 350 EUR machine whereas Rancilio Silvia is 600 EUR machine. These are not entry level machines. They are entry level for someone becoming more interested in espresso but not for ordinary people. And ordinary people do not spend 400-500 EUR for a coffee machine if they think they are going to get the same for twice less money. Twice less money machines do not have OPV.

> These are not entry level machines

Yes they are. To put some perspective, my current machine (Bezzera BZ10) costs about $1,700 USD and it's not even close to being a high end machine.

Respectfully, you don't know what you're talking about. Even the Delongi Dedica, which is at the bottom end of espresso machines, has an OPV valve.

Without a pressure release, they might explode right? Seems bad, I would expect it to be standard equipment.

They are not going to explode but on such machines if you remove the portafilter straight after extracting the espresso, the puck will "explode" and is going to create a mess. In more expensive machines this is regulated through OPV and solenoid valve through which the pressure built up is going to be released.

Nespresso's taste is least likely to be anything anyone is looking for in a good espresso.

That high pressure causes some odd taste notes and it would cause channeling in the puck. Not to mention all sort of other issues which start already at ~11 bars.

I’ve found there to be a distinct taste to Nespresso and go some way to avoid it (literally in some cases, it’s in cafes all over Europe). I’m not sure if it’s the coffee container or the high pressure and bean combo but it’s taste is not something I’d ever aim for.

I strongly believe that the Nespresso was designed to solve/create a problem to fit their business model.

In this order: Proprietary, good margin, small foot print (pods and extraction unit), easy to use, disposable.

That Euro cafe served nespresso coffee is different then the nespesso capsules for making espresso. I've had so I understand what you mean. The nespresso pod machines, it sure is a razorblade model but you can get quite and varied espressos.