I am looking to expand my solar system. I currently have the discontinued Enphase M250 micro inverters on my solar system. Can I add on Enphase IQ6+ micro inverters?
No, the IQ series is only compatible with other IQ products. See our article Enphase IQ6 vs IQ6+ Comparison on the differences between the two Enphase IQ micro inverters. You would be able to do one of two options:
Add either Enphase M250 or Enphase M215 onto the trunk cable. While both models are discontinued, we do have some of the Enphase M215s still available for purchase (at least at the time of writing this article).
Have a separate parallel IQ system. Note that this will require separate breakers, different monitoring and other additional equipment.