Low rpm gasoline generators. Coleman Vertex 5500 (other versions would probably work well too) hack really seemed to be super fuel efficient when i put a zip tie around the throttle to keep it at a lower rpm. the fuel tank will last months not in direct sunlight and its super quiet.
Works great for construction projects when one person is using it. would try and use this to power an electric car even. probably makes almost 1 kw at idle probably suposedly its a 1.5kw generator on the bottom yet produces 5500 watts.
!Also kink the fuel line. forgot to mention earlier the hose has some wire on it if you look. it prevents the jet from spraying as hard i think or keeps a vacuum on the line and idles better slowly dripping in maybe using half carb or pulses of gas. (i might have found the sweet spot by letting it run out of gas where its just using fumes)
to try it on any generic generator just pinch the fuel line a bit and hold it at idle or near idle with a device plugged in using power. dirty power(possibly dips lower than 60hz but still very usable for most devices if you need more plug an inverter into a battery charger or something along those lines)
wenkel washing machines
other pm generators
static electricity devices