Hi Ann the input control is how hot the surface of the heater will get. The output adjusts the opening time of a flap on the top of the heater core so an early boost would mean that this flap would open letting more heat out much earlier than a late boost but this also depends on how hot the heater is. The most economical way is leave it off and then use it like a switch in the evening when it is needed, turn it up to early boost for max output remembering to turn it back down before bed time. I worked for the electricity board on these heaters and my advice was always remembering the higher the number the more it will cost. I still use this type of radiator myself.
Her is a good page for explanation Ann, I hope it helps it’s from southern electricity. Walke40
copy and paste it.
http://www.southglos.gov.uk/NR/rdonlyres/71D38653-66ED-416D-BDBC-37470E0B0364/0/HSG070077.pdf
Walke40, May 2010
