Depending on the appliances and equipment being used in the food truck, a 4000-watt generator should be the minimal size to consider for optimum efficiency and effectiveness.  This should allow for all appliances to run at full load without peaking the generator’s output. It is suggested you get a generator with a bit more power, of between 4000-7000 watts, if you intend to run multiple appliances, to give you that extra bit of capacity.