A couple of years ago, I was asked for input on a proposed heating system in which two electric boilers were being added to a school’s heating system. These new electric boilers would supplement the output of the existing gas-fired cast-iron boiler, and take advantage of low “off-peak” electrical rates.
The load was four zones of low water temperature floor heating. Great! Lower water temperatures allow most heat sources to operate at higher efficiency. However, this is not the case for electric boilers. For them, 1 kWh of electrical input yields 1 kWh of thermal output regardless of water temperature.