This is a simple, but at the same time complex question. If you install a system with the intention to increase to a larger system in the future, you need to research your initial installation. It’s easy to say “just add a few more panels” but if you haven’t planned for it, you may be in for a shock.
In most cases, the inverter will also need to be upgraded, which is an expensive exercise. So you’ve planned in advance and installed a larger inverter in anticipation of upgrading… Also a bad decision as an underpowered system will be extremely inefficient until you upgrade. If you really want to take this approach, then we suggest taking a good look at the inverter specifications.
- Traditional inverters: You need to start with an inverter that has a minimum of two MPPT strings, for example a 4kW SMA inverter has two 2kW MPPT strtings which means you can fill one string (2kW) now and get the maximum performance from that string, then add another 2kW at a later date. This scenario works but you must add the whole 2kW at a time to ensure you don’t lose efficiency throughout the process.
- Solar Edge inverter: All Solar Edge single phase inverters (up to 6kW) will function at 100% efficiency with just 1.5kW of panels connected. This gives you the flexibility of adding as much as you want or as little as you want at a time. That’s right; you can add just one panel at a time until you reach the maximum. This is accomplished due to the Solar Edge philosophy of employing MPPT at the panels, not within the inverter.