Quote:
Originally Posted by nybbler
But how much less did it run between 7am and 4pm?
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That's irrelevant but I think it is what too many people get hung up on. It ran less during the day, but longer that evening. Any savings that we may have recognized were negated by the additional run time to bring the house back down from ambient room temperature.
On the Saturday we tested, the unit ran for 3 hours between the hours of 7am-8pm.
On the following Sunday, the unit ran for 3.98 hours between the hours of 7am-8pm.
Let's say you only use this schedule during the work week, that's an average of 22 hours per month of additional run time for the unit. (I know other variables come into play such as temperature, clouds, etc but not enough to negate 22 hours)
My heat pump is a 4 Ton Rheem package unit. It uses 14 KW/h.
On a normal July month between 7am-8pm it runs an average of 92.4 hours. We pay $.09 per kw/hr. The average cost to run the HVAC is $116.42.
If we follow the method of adjusting the thermostat, it would run on average 114.4 hours per month between 7am-8pm. At $.09 per kw/hr the average cost to run the HVAC would be $144.14. That's almost a $30 cost increase to let the system run less during the day when we aren't home.