I've noticed my HVAC usually runs three times per hour around 7 minutes each.
>duty cycle = 7/20 = .35, period = 1/3 hour.
If I leave my heat on at the same temperature 24 hours a day, it will run 504 minutes a day and have to turn on 72 times.
>translate 504 minutes to 504 'units' of fuel, so when on the furnace consumes 504/.35 = 1440 units in 24 hours = 60 units/hr. = 1 unit/min.
If I turn it completely off for the 10 hours I'm away during the day and turn it on when I come home, it will run 354 minutes in a 24 hour period. . .
to turn on around 40 times
>the 24 hours includes 14 hours at .35 duty cycle which means 4.9 x 60 u/hr = 294 units of fuel.
>the 10 hours off consume 354-294 = 60 units.
>the one hour reheat takes 60 units.
>this leaves nothing for the 40 times.