If power consumption is low and the solar is able to offset the power bill entirely the solar power is not fully utilised and selling back electricity to TNB is usually at a lower rate, it will have longer ROI.

If power consumption is high, then the solar power can be fully utilise, provided the panels are facing the correct direction and scrub wash every 2-3 months for maximum generation efficiency. Without batteries, only power consumption during the day can be offset while residential power consumption are usually higher at night with the A/C switched on. Having batteries will help offset daytime generation to night time consumption, with added cost of course but it will allows better utilisation of power.