our oil company tells us we can't shut off the furnace as we have a tankless water heater attached to the furnace. We are away most of the summer so are paying for the water to heat while no one is using it. Why can't we shut down the furnace while away?
I also have an old hot water boiler that has a domestic hot water coil that makes continuous hot water. You can turn off the boiler and save oil, but there will be no hot water unless it is on. I turn mine off and on all the time because its a summer house and when its gets real hot a warm/cool shower is fine. Sometimes we turn it on for showers,dishwasher,washing mach. then turn it off in the summer.