MPG drops 50% when AC Blower is On

To all readers and contributors, thank you in advance for your time and help, now and in the past. Long time lurker here, but I finally made an account today after hitting nothing but dead ends on this issue.


Short Story:

2013 Prius C Three. 147,000 miles. MPG averages @47-49 (up to @60 if trying) when AC blower is off. This drops to 27-33 MPG when heating or cooling is on. MPG gets worse as I increase the speed of the fan. Any ideas?


Long Story:

This issue started around 135,000 miles. The dealer advised that this was just the cost of using the AC in the summer and that I had just never noticed. They would not offer any possible solutions unless a CEL came on.


Fast forward 4 months to @146,000 miles. I popped a CEL. The Hybrid Battery was dead. The car still ran fine on the gas engine. Over @200 miles I was getting @30 MPG with no AC, closer to 20-25 with the AC on. Despite the CEL, the car never stopped running fine on gas only.


Toyota quoted @$4,000 to replace the battery. I requested a good will discount from corporate and they only came down 15%. And they would not guarantee that this would fix my original MPG issue.


After reading reviews, getting multiple quotes, and understanding the risks, I opted for a rebuilt battery swap from a shop in LA. $1,300 with a 3 year 45,000 mile warranty. And I paid with my AMEX just in case they wouldn’t stand behind their warranty.


Now, about 1,000 miles into the new battery, I’m back where I started this summer, perhaps slightly better. The car works nearly as efficiently as when brand new, as long as the AC blower isn’t on. Turn it on, and I’m getting at least 100 miles less per tank.


The dealer and 2 local shops will only recommend putting in a new factory hybrid battery for @$3000-$4,000. Only then will they consider diagnosing any potential, but likely imaginary they say lol, additional problems.


The only thing I can think of is to replace the AC blower motor and see what happens. Any advice?