The size of the generator needed to power a house depends on the power needs of the house. To determine the size of the generator needed, you should estimate the total wattage of the appliances and systems you want to power. You can find the wattage of each appliance in the owners manual or on the appliance itself. If an appliance has a motor, you will need to calculate the total wattage using the formula: Running Wattage (R) = Watts x Volts and Starting Wattage (S) = R x 3. Once you have the total wattage, add the numbers together to figure out what size generator would be right for you. A generator that can provide between 5,000 and 8,000 watts would be enough to power a typical house. However, the size of the generator needed may vary depending on the size of the house and the appliances you want to power. It is recommended to choose a generator with a capacity that is 10-20% more than your demand, whichever number you come up with. Choosing a generator that is too small can result in power failure and damage to the unit, while a generator that is too big can be wasteful and not cost-effective.