Well I actually work as an Solar Design Engineer out here in California. Interestingly, what I found was Photovoltaics is actually not new technology, it actually has been around for almost a hundred years. It is true that initial start up costs are high, however, the system has a life-span of 25 to 30 years, and your ROI in Malaysia would be about half of that (Actually, I'm going to say this depends on how much of a utility bill you get in the first place). In California, there are government based and utility based incentives to help balance the cost of Solar systems here and ROIs can go from 4 to 7 years depending on the size of the system. Though, it would be unfair for me to point on California's case.

It is true that power is not produced during the night, however you would be surprised that power can still be produced in cloudy weather, though production may be halved or even more. However, all these would have already been taken into account in the first place when sizing a system, so your building/house would be covered. Also, do keep in mind that renewable energy systems will definitely not take over current forms of energy, but it would actually mitigate the amount of coal being burnt, hence making KL's skyline more visible at times.

Efficiency of panels range from 18 to 20 percent and its bound to only go higher. Especially with the recent boom in the European market again due to large incentives and not forgetting the large American market. Prices on PV panels are now so competitive due to the over production in China.