This example build of a 2014 Ford E-350 was done by Catpain-Built. Images used with permission.
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My 12ft Box Truck. 100% built by me. 1k watts solar, 1120ah lithium batteries, tankless water heater, and mini split a/c.
12ft long 6.5 tall. 7200 lbs. 3265 kilos.
Once the a/c cool the space, it idles around 10-120w.
I have a diesel heater for heat. The mini split can heat but it burns up wattage.