The size of the generator determines the type and number of appliances you can power at once. You need to work out the amount of power you need to not only run your appliances, but to start them. For example, an electric drill might need 1000W starting power but only 500W to keep it running. You can find this information in the appliance user manual. Check the power requirements for each of the appliances you intend to run off the generator at any one time. Total the running power loads. Then look at the appliance with the highest starting power requirement and add this figure to the total. You need to choose a generator that produces more power than this figure. Remember – do not overload the generator, as this may cause damage to the generator or worse still, damage the connected equipment.