If depreciation is a major concern, an EV or PHEV may not be your best choice (short of some exceptionally good regional or seasonal sale price).
A good way to start the estimate is the moment you drive off the dealer lot, the used value should be reduced by the going federal incentive plus any local incentives, which for a Clarity might put you at around minus $9k. Also, take another percentage off for just converting a new car into a used car, probably in the $1k to $4k range.
Other factors (bad) could be if Honda dumps the last of them (2019, 2020, 2021?) at deep discount. That would, at least momentarily, depress used prices.
As of now, after a year, you would be lucky to get $24k for a used Clarity. On the other hand, if you got the incentive(s) yourself, then you can take those out of the equation when considering actual depreciation as personal cost.
Then, the EV part is the more years out, the more likely that the technology, especially battery capacity, will improve, making say a three to six year old EV less attractive.
An additional complication with Clarity is that nobody knows how long the Clarity model will be available, or what that might mean for depreciation. One good Hollywood movie Clarity with relatively small production numbers could be good (like a Delorean?). More likely, in eight to ten years, they will have little monetary value.
Possible good outcomes (depreciation less of a concern) include if you happen on one of the exceptional Honda Clarity lease deals (if you are good with two or three years), or you buy one, fall in love, and keep it for ten+ years.