Wrap it up!

“If your water heater is more than 15 years old, install an insulating wrap to reduce "standby" heat loss. It's also a good idea to insulate hot water pipes where they're accessible.”

https://www.powerhousetv.com/EnergyEfficientLiving/EnergySavingTips/101WaysToSaveEnergy?utm_source=WS&utm_campaign=Energy-EfficientLiving/Energy-savingsTips/027471