Does a good cup of coffee need to start with cold water? My father-in-law just got a Keurig machine and he insists on putting ice cold water in the reservoir in the morning. It gets heated up anyway so you’d think it wouldn’t matter.
You can check the answer of the people under the question at Quora “keurig coffee maker hot and cold“
The water in a percolator has to be at least cool, say 65° F for it to brew properly.
I catered a wedding once where the air temperature was 107° F and the tap water was about 90°.
Coffee percolators are controlled by a thermostat and when a certain temperature is reached, the heating element shuts down. The coffee makers were shutting down in about 5 minutes, and what they produced was barely brown in color. The grounds were mostly dry. These were 100 cup commercial coffee makers.
We unplugged them, took the grounds basket out and dumped out half the water and added ice to bring the liquid volume up to the right level. Put the baskets back and tried again. It worked fine.
If you’re wondering who would want to drink coffee in weather like that, it was conservative Baptist wedding in a small town in West Virginia about 3.5 hours from the DC area.
I don’t know of any other reason to need cold water especially in a Keurig type machine.
Your FiL is simply wasting energy.
The starting temperature of the water has absolutely no effect upon the final product. Water quality does make a difference, but that has nothing to do with its temperature.
Also as the heating element has to work longer, it will wear out faster.
I put in cold water but not ice cold. Does it make a difference, I have no idea, it just seems the right thing to do. In any case I use distilled water so I don’t have to worry about clogging it up with minerals. I have the water in bottles and it is room temp.
The heating element of the coffee maker is a fixed wattage. If the water is too warm, more water is “boiled” per unit time. The generation of steam at the heating element forces the water out of the reservoir and through the capsule or grounds holder (for other thypes of machines). Since the water is boiled quickly, the throughput is too high, and the dwell time (water with the grounds) is too low for good extraction.
Control of the time of extraction is one reason people like French presses – you add the grounds, then the boiling water, and you time the extraction to get the end product you want.