I've been using one for the past three years in our EV. It works well as 
long as the inside temperature is in the 60s or 70s. However, as you may 
know these coolers/warmers keep the temperature in cool mode about 40 
degrees F below the exterior (to the cooler) temperature, or in heat mode 
about 40 degrees above the exterior temperature.

So if your van is parked in the sun and the interior temperature starts 
rising above 90 degrees, essentially your cooler turns into a warmer. I 
don't see these coolers as replacement for a regular refrigerator for long 
term use for that reason. We do get around the problem to an extent by 
putting a frozen bottle of sparkling water in the cooler when we know the 
van will be sitting in the sun for a while, otherwise if we don't our food, 
etc. gets "cooked".

Hope this helps.

Ric