I am trying to do a rough calculation of how much I would save replacing 18 year old heat pumps.
A sample would be a 3.5 ton split system heat pump. A basic new one would be 13 SEER. What would the old one from 1994 likely be? 8 SEER?
I know how much I save would depend on how much load (and therefore how much they run) but is a 13 SEER 50% more energy efficient than an 8 SEER?
Is there a rule of thumb on energy savings from a higher SEER?
Thanks very much