Just because its not multispeed doesnt mean it isnt as efficient as you
can get now. what is it rated, or look inside the unit or on the papers
and find input and output btu and calculate it. 94.5 %- 95 is about as
high as they go . Even Carriers 96.7% line is BS as only the smallest
unit 38000 btu is 96.7% the rest are near 94.5%. If you have had it
cleaned and maintained it should be fine. VS DC motors save electricity
but you need the 10 yr warranty.