What gauge wire? Enphase solar

I have two trunks entering an enphase combiner box. Each using IQ8+ and having 6-8 300w panels. So each trunk is on a 15a breaker. From the combiner box I need to make a run back to my main panel about 100ft away. I’m thinking that should use 10awg wire. Do we agree? Or should I use 8awg in case I upgrade panels in the future?