Does it matter in terms of energy usage whether my gas heater is set to higher or lower temperature?
Situation: - 2 floor house, all water radiators heated by the same gas boiler system
-1st floor has gas heater, radiators without Thermo heads, and a single thermostat attached to heater set for day/night temperatures (21/19C). 1st floor is also not renovated (yet) and has higher heat loss through old windows, cold floor (not enough isolation from a wet basement I think),etc.
-2nd floor has radiators with thermo heads each set individually but basically within the same range as downstairs thermostat day setting.
Now, I can set the gas heater to heat the water in a range of approx 30-60C.
The question is, under the above conditions, does it matter, in terms of gas expenditure, if I set heater for higher water temperature or lower?
If I set it for lower, it will take longer to heat the rooms, but (I assume) use less gas during heating process. In addition, it only needs to turn on every now and then when the temperature drops below thermostat point.
I guess I can try to look at gas meter one way and then another, for a week or so, with taking in account also outside temperatures, but is there maybe some rule of thumb?