Heat loss from uninsulated pipes = ΔT × heat loss factor × pipe length × hours.
A bare 10m hot water pipe (80°C) in a 20°C room loses ~8,760 kWh/year.
Good insulation reduces heat loss by 70–90%.
A bare 10m hot water pipe can waste over 8,000 kWh/year — costing $960+/year at $0.12/kWh.