A friend dropped me this email yesterday, asking for some advice (slightly edited):

We spent a lot on oil last winter.  We have a 23 year old heat pump which gives us A/C in the summer, but no heat any longer.  I had a proposal from the installer for a new 14.5 seer heat pump replacement.

Here is the question: how much more efficient will that unit be compared to our old unit?  We are not convinced that it is worth the cost, so we thought you might give us a ball park estimate of potential savings.  Bottom line is enough: does this sound like a good decision?

This is such a great question, that I wanted to share it, and my answer, with the rest of you.

Let’s start with the basics – what is a heat pump?

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