I wound up with the 24" Insignia 720P on sale for $139. A little bigger viewing area for our aging eyes....and can't really tell the difference between 720 and 1080 at that screen size anyway. Interesting that the 22" and 24" both have the 12v wall warts, but the 19" has an internal power supply with a 120v cord.
The 24" says 36W power consumption.
One last question on the installation: I have a Samlex 150 PSW inverter wired via 15A transfer switch to power one circuit in the RV, and the outlet for this TV happens to be on this circuit. I have 2 options:
1. Eliminate the wall wart and plug the TV directly into the lighter socket at the antenna jack. This does mean the set will see higher voltages when plugged into shore power and charging.
2. Keep the wall wart and plug into the inverter powered outlet. Downside is that since this is the bedroom TV, the inverter will stay on all night since nobody (me, LOL) will get out of bed to shut it down. The inverter draws 500 mA at idle, how meaningful of a parasitic draw is this?