Thanks for your question. It depends on the size of your home and how much your combined household appliances will draw. You can get an electrician to take a reading on your house and the overall power it draws. Typically 8kVA to 13kVA will power most things in a standard home, e.g. your lights, fridges, freezer, computer, television, fans, kitchen appliances etc. When you start adding larger wattage appliances on top (e.g. Washing Machines, Dryers, Air Conditioners etc.), then you may need a larger unit. Again, 8 to 13kVA will work for most homes, but it depends on your particular home and the appliances.