Shorter waiting time for hot water

If you can reduce the pipe size or length between hot water tank and shower + hot water taps, maybe you can save quite a bit. If you can save just 30 seconds in waiting time with tap and shower open with 10 ltr water/min and you need hot water 4 times/day, you will save 20 ltr/day of hot water equal to 7 m3/year. This will save around 360 kWh/year.

The example is for replacing 18 m of DN20 mm tube with 18 m 12*2 mm PEX tube that costs 1 €/m = 18 € + work to replace it, total around 40 €.