I have a small generator and I fixed a socket source outside my apartment for public charging of phones for my neighbors so as to have privacy in my room. But, what's surprising me is that if I fill my tank with 4 liters, it use to drain fast so I'm thinking maybe it's because of the people charging outside.

One phone with 2a charger is 10w, 1a is 5w. This means if you charge 10 phones with 2a charger at a time that is 100w. Add the 100w to your load of about 200w or more that is over 300w. More load means more fuel