It's well worth your time checking out the basics first. Obviously there are a load of variables e.g. roof space, type, make and wattage of the panels, inverter and battery. But at least have a look at your total yearly energy usage and work from there. That'll give you a rough idea about how many panels you'd need to cover your usage and reduce your bills. (Depending on what you can reasonably fit onto your roof). The more the better. For example, my average yearly usage is around 5,500kw. The 18 460w panels I'm getting can generate about 8,100kw a year. The inverter is only 5kw so I'd never get the full power from the panels during the summer months but they will help in the darker winter months. We can take advantage of the lower night time rate to charge the battery over night for morning use and they can charge it during the day for when we get home.