I have a new Amana 220v 12,000 window heat pump and a 6 year old 4 ton Goodman heat pump which is over-sized for our 2,000 sq ft house. The electric bill is running about $300 per month with the central air alone.

I did a test and the window unit seems very capable of keeping the entire house cool with the central air blower running full time when ambient temps were below 90. I realize the window unit may not keep up by itself when temps get over 95. Am I saving any money using the window AC with the central air blower? When winter comes will using the window heat pump with the central blower save money?

 

Welcome to the forums.

Not running the big heat pump will technically save you money.

The window heat pump will not have enough heating capability to heat that house.

 

if you have leaky ducts in a basement or ducts in a hot attic, the window unit will save you money over running the central.

Especially if you're comparing a energy star window unit to a older 8 to 10 seer central a/c.

A lot of central air systems are poorly engineered, installed and commissioned, so they don't perform as they should.

Done right, these systems can be very efficient.

 

Thanks for your help! Being in MS the fall/winter is pretty mild so the window heat pump may work on mild days.