The current FEH has its own heating and cooling (air conditioning!) system. The software limits the hybrid battery SoC to normally range between 40-58%. It is possible to sometimes exceed the upper limit (downhill) but Ford put this limit in to preserve longetivity. There was a thought the 2008 FEH has a range of 35 to 65% hybrid battery SoC but this remains unconfirmed.

There is an individual in Indiana who has hacked the Prius software and piggybacked two hybrid battery packs for a PHEV.

2005 AWD Escape Hybrid
Best tank trip MPG 39.02 (scangauge II) for 402 miles on I-70, 10.3 gallons used over mostly flat terrain.

Best tank trip MPG 34.6 for E30 for 271 miles along I-80 in Indiana and Ohio.