mgthompson wrote:... the nagging thought in the back of my mind is "How accurate is it really?"

To clarify, the Duetto's brew temperature is quite precise, i.e., it reproduces the same temperature each time. Whether it is accurate, i.e., does it produce the displayed brew temperature at the grouphead depends on how accurately the PID's offset matches reality. This distinction is shown below:


High precision, low accuracy

Long answer: Accuracy is important if you wish to compare results with another person who has provided the target brew temperature. Precision, in my opinion, is far far more important. Once I've established a starting temperature what works for a given coffee, the digital display could say "X" and "X+1" for all I care, as long as the "+1" really means it increased by 1 every time. In my research for the Izzo Alex Duetto V3 Review, the Duetto was quite precise. The accuracy of the displayed temperature compared to the readout from a Scace thermofilter was acceptable, i.e., the digital readout from the onboard PID and the measured temperature at the grouphead tracked closely. IIRC, they diverged slightly at the higher end of the settings. That is, the onboard readout would match the grouphead readout exactly at 200F, but when setting the PID to 203F, the grouphead reading was slightly lower. I didn't really quantify this minor divergence since it was consistently repeatable at a given setting.

Short answer: If you really want a good idea of the delivered brew temperature, a grouphead thermometer is a lot cheaper than a Scace thermofilter. I don't think you need a grouphead thermometer for tweaking the brew temperature on a Duetto since the digital readout is nicely repeatable. Thus, in my opinion, it boils down to a wants vs. needs decision.