I have been very involved in maintaining my Quaker Meeting House in Damariscotta, Maine for many years. I have helped to "green" the building in many ways, from adding a modest solar power system, to many efficiency upgrades. The building was constructed in 1995 and was built with "traditional" construction and heating system. This means that it uses an oil fired boiler like many buildings and homes in New England. So about 10 years ago we decided to switch to a B20 (20% biofuel) mix that became available in our area. Higher biofuel ratios do not work well in frigid temperatures because it can congeal and also corrode seals.
But then we realized that the water heater is tied in to the huge oil boiler and the boiler was running during the warm seasons to heat a 30 gallon tank located in the cool basement. In this environment the tank loses heat and needs to be "topped up" fairly often wasting a lot of fuel oil to heat water that was not being used. So we came up with a work-around. We had a small 4 gallon electric heater installed after the hot water tank. Then we installed a timer that only runs the oil "boiler-mate" for hot water on Sundays when we need more for dish washing and events. When the tank is not being heated by the boiler, the stored water is tempered by the ambient environment, thus raising the temperature of the well water from a nominal 45-50F to 50-60F. This reduces the load on the small electric heater a little.
Now the modest weekday hot water needs are met by this small electric heater. Due to the Regional Greenhouse Gas Initiative (RGGI) in New England, the electric supply is supplied from at least 45% renewable sources such as hydro, solar and wind. So this is a win from a cost, carbon footprint and efficiency standpoint.
All this came up when someone noticed rusty water coming from the hot faucets. I drained water from each tank and determined that the small electric unit had rusted out inside. Our local plumbing company wanted $400 for a new heater, plus labor. This seemed unreasonably high so I found a nice Bosch unit on Amazon Prime (free delivery of a 20+ lb package!) for under $200. It took me about 20 minutes to replace the unit.
But then we realized that the water heater is tied in to the huge oil boiler and the boiler was running during the warm seasons to heat a 30 gallon tank located in the cool basement. In this environment the tank loses heat and needs to be "topped up" fairly often wasting a lot of fuel oil to heat water that was not being used. So we came up with a work-around. We had a small 4 gallon electric heater installed after the hot water tank. Then we installed a timer that only runs the oil "boiler-mate" for hot water on Sundays when we need more for dish washing and events. When the tank is not being heated by the boiler, the stored water is tempered by the ambient environment, thus raising the temperature of the well water from a nominal 45-50F to 50-60F. This reduces the load on the small electric heater a little.
Now the modest weekday hot water needs are met by this small electric heater. Due to the Regional Greenhouse Gas Initiative (RGGI) in New England, the electric supply is supplied from at least 45% renewable sources such as hydro, solar and wind. So this is a win from a cost, carbon footprint and efficiency standpoint.
All this came up when someone noticed rusty water coming from the hot faucets. I drained water from each tank and determined that the small electric unit had rusted out inside. Our local plumbing company wanted $400 for a new heater, plus labor. This seemed unreasonably high so I found a nice Bosch unit on Amazon Prime (free delivery of a 20+ lb package!) for under $200. It took me about 20 minutes to replace the unit. 
