The water in the supply line will not be hot if it’s had a chance to cool down after the last use. Typically the water in the supply line will take 3-5 seconds to flush out with hot water.
The size of the incoming gas line required for your tankless unit could have a big impact of the installation cost. Most water heaters have a 1/2″ supply line for the incoming line. Many tankless units will require 3/4″ gas line in order to meet the demand of tankless units. Each situation is different and should be assessed by a licensed gas specialist.
The life expectancy for a tankless water heater is about 20 years but will vary with water quality and overall water consumption.
A tankless water heater should be flushed out just like a regular water heater should be flushed out to maintain efficiency. The process for flushing out a tankless water heater is a little more involved and requires a pump, vinegar, and a few buckets. This process should be completed at least once every 12 months.
Typically electric tankless water heaters don’t produce enough energy to meet the average demand of a household. The Kansas City climate gets too cold in the winter time for most electric units to keep up with.