You are missing a factor of 24, which comes in because they said "0.155 miles per day on battery power".
The easiest way to do the calculation would be, assuming a Prius Prime can do M mi/kWh on battery power, is to calculate 0.155 mi/day x 1/M kWh/mi x 1 day/24h = 0.0065 kW = 6.5/M W. That gives us W which can directly be compared with the 2 W he gave.
Also, 1.42 mi/kWh seems way low for battery power operation. I'm pretty sure that is for mixed gas/electric operation, expressed in MPG-e (47.9) and mi/kWh for convenient comparison to pure EVs. (You can convert between MPG-e and mi/kWh used the conversion factor for 33.7 kWh/gal.
It has a 13.6 kWh battery and a 39 mile all electric range, which suggests M = 2.9 mi/kWh. Plugging that into 6.5/M W gives 2.2 W.
M is probably actually a little higher because the car probably doesn't let the battery actually use 100% of its capacity. Most sites I see seem to say 3.1-3.5 mi/kWh.
On the other hand there are some losses when charging. On my EV during times I've the year when I do not need to use the heating or AC the car is reporting 4.1 or higher mi/kWh, but it is measuring what is coming out of the battery.
When calculated based on what is coming out of my charger it works out to 3.9 mi/kWh. This is with level 2 charging (240 V, 48 A). Level 1 charging is not as efficient as level 2.
If we go with 3.1-3.5 mi/kWh, and assume that is measured on the battery output side and that the loses during charging are about 8%, we get 2.9-3.2 mi/kWh on the "this is what I've getting billed for" side. If we use the average of that and plug into 6.5/M W we get 2.1 W.