This can be an economical alternative to a large stand-alone system, since it does not have to be sized for worst case weather conditions. A petrol, LPG, or diesel generating set combined with a battery charger can supply power if the batteries become low. The generator can also power peak loads, giving savings in inverter cost and allowing a smaller battery bank to be used. Often for places without any mains electricity a generator will be the existing source of power so adding a battery store with inverter/charger and additional wind and/or solar generation is the perfect way to reduce fuel costs and to make 24hr a day power available without running the generator all the time.