Yes — both can be added, but timing and platform choice matter.
Solar panels: Add anytime to available roof or ground space; new strings tie into existing inverter capacity.
Batteries: Plan additions within about three years — after that, specific models may be discontinued and compatibility gets harder.
100UP’s usual approach: oversize the solar array upfront (cost-effective, maximises rebates) and install a lean battery bank for current needs. You harvest more power now and add storage when budget or load increases — without a full redesign.