Better late than never I suppose.
Tankless water heaters will raise the temperature of the water by X amount. This means one has to take into account the temperature of the water going into the heater as well as the heaters specifications to determine how hot the water will be heated. If the water was at 40 degrees, which is unlikely, a unit that heated the water by 40 degrees, will only get you 80 degrees of heated water.
When we built our house, we really wanted a tankless water heater. In the end, we just put in a tank water heater because it was cheaper at the time and it was the better solution for us. We do not have gas or propane at our house. The gas/propane tankless water heaters had a much greater temperature rise than electric. The units we looked at 10 years ago just did not look like they would heat up the water enough.
A few years ago, we were talking with the plumber who worked on our house and he said he will NOT install a tankless water heater in a house. He has had too many problems with them. I can't remember if he mentioned the problems but I would guess hard water is an issue. Another advantage of a hot water tank heater is that it stores water which comes in handy if you are on a well and loose power. We have drained water out of the tank on occasion when we were without power.
We have very hard water and I have to run vinegar through the coffee maker every few months to clean out the piping.
My coffee maker started having problems after the last vinegar cleaning. Now the appliance is so old that the lettering for the buttons has worn off so the coffee maker may have been on its last legs in any case. I researched coffee makers and I did not like what I was reading in regards to the coffee makers quality, reliability and cost. In the end, I bought a stainless steel funnel and 1 quart/liter pyrex measuring cup for $20. I heat one quart of water in a 1500 watt microwave for eight minutes to get the water to 190-200 degrees and pour the water over coffee grounds that are in a basket sitting in the funnel which in turn is in the coffee pot or thermos. Works just fine, was cheap, tain't gonna break, travels well, and makes the best coffee I have ever had.
I have taken the setup to a couple hotel rooms and it works just fine. I take an instant read thermometer to make sure the temp is right. Pretty danged easy, cheap , and a multitasker.