Also, I think the Clarity has a heat pump heater in it, so make sure your AC use is enabled, as the heat pump and the AC are the same thing. It is possible that if you disable the AC it won't pre-heat properly. I am not certain on the heat pump, but it does show on the Honda information page under the Driving Range FAQ:
https://automobiles.honda.com/clarity-plug-in-hybrid#maximize-range
I will mess around with mine some too, but haven't had much chance yet. Honestly, the heater blows hot air so fast (like 50 feet from the house), that I don't see much reason to preheat it and I don't get to drive it very often
My wife did say the fan is making a rattling noise at temps less than about 0 F.
However, this could be a copy paste error from the Clarity BEV which says the same thing.How do I maximize my range when driving the Clarity Plug-in Hybrid?
The Clarity Plug-in Hybrid features energy-smart climate control technologies, an efficient Heat Pump, eco mode, and multiple levels of regeneration to help maximize your driving range
https://automobiles.honda.com/clarity-plug-in-hybrid#maximize-range
I will mess around with mine some too, but haven't had much chance yet. Honestly, the heater blows hot air so fast (like 50 feet from the house), that I don't see much reason to preheat it and I don't get to drive it very often

My wife did say the fan is making a rattling noise at temps less than about 0 F.