We plug in the Fusion Eneri every night, after 7 years and 105,000 miles it's still has 93% of it's original capacity. The 90% rule applies to BEV's like my Mach-e.
You are going to love it, my wife has a 2016 energi we bought new it has been almost trouble free for 90,000 miles. Long term ave mileage for her is right at 55 mpg.