Should I change my old solar system, add panels or add a new one?

Should I change my old solar system, add panels or add a new one?

  1. Adding more panels using your inverter: you can have a solar system up to 133% bigger than your inverter to still be eligible to the STCs financial incentive. The challenge here is:
    1. Unless your original installer does the upgrade, the warranty of your older system will be cancelled.
    2. You will need to find the same of similar solar panels to add to your system. 
  2. Purchase a bigger inverter to add even more panels 
    1. You current inverter is a brand that is not recommended anymore and this would be a great opportunity to replace it with a better one, such as Fronius, SolarEdge or SMA.
    2. You can add different panels to your existing ones by getting an inverter with 2 inputs instead of one. Then you should get an inverter with SUNSPEC/MODBUS (so it can "communicate" with both your solar arrays). 
    3. Inverters are not eligible to the STCs, but your new solar panels are.
  3. Getting an additional solar system working next to your older one
    1. This way, you can keep both warranties intact. 

It all comes down to the reason you'd like to add more panels and on how much space you have on your roof. You can now have 400W panels installed, that will be producing almost double the energy as your older panels. 
Regarding installing a battery, it depends on how much excess solar energy you've got at the end of the "solar" day. Batteries are quite expensive at the moment and unless you have a big solar system (7kW+) and consume lots of energy in the evening, we would not advise you to get one. Instead, make sure all your big appliance run during the day.