If you need more power you have 2 options. You can add more batteries in parallel and increase the size of the cables to take the higher current, or you can go

If you need more power you have 2 options. You can add more batteries in parallel and increase the size of the cables to take the higher current, or you can go to a 24 volt system which means you can use the same cable. 24 volt components are maybe harder to find though. My system is really intended for short periods of peak power (say 30 minutes a week running the mower). It was harder to find cheap inverters to handle more than 1kW at the time too.