For running a 13,500 BTU A/C and if you really don't want to install an Onan 2800 generator or carry a portable generator then look into under the hood mounted generators. One of these might be what is used in the E-trek
Mobile Electric Power Solution, Inc. (MEPS) -
http://www.meps.com/products.htmlAura Systems Inc -
http://www.aurasystems.com/pages/prod_intro.htmlRaven Technology -
http://raventechpower.com/Fabco Power -
http://www.fabcopower.com/generat/bgen.htmIt might be best to have an Onan 2800 generator installed under your Roadtrek though.