Hot Water Heater Blanket 48" X 75" Water heater insulation can significantly improve the efficiency of your water heater. This foil-backed fiberglass insulation blanket is designed for gas, oil, and electric water heaters up to 60 gallon capacity. Adding insulation to your hot water heater can reduce standby heat losses by 25% to 45%. This can save you around 4% to 9% in water heating costs. * Please measure your water heater before you order to make certain this standard size will fit. If your water heater is larger, we can custom make any size to order. Just call us for specifications and pricing.