There are many considerations to take into account when you are designing a solar electric system. And growth is one of the considerations. Perhaps you design a system to suit your current electric usage, but then want to add an electric car into the mix. So the question is can you add to a solar electric system. The answer is a qualified yes.
Discuss you current and potential needs with your design consultant. Design the system with a large enough inverter to handle future loads and additional modules. Perhaps you hope to add batteries in the future. All of this is significantly easier if your start with the end system in mind.