Singapore Wholesale Electricity Price and PowerWall (Home Batteries)

Just a random thought that came up... We have the Singapore Wholesale Electricity Price (WEP), which fluctuates every 30mins. But articles have pretty much shown that they are, most of the time cheaper than the Open Electricity Market (OEM).

While someone who lives on a landed property, with a roof, could install solar panels and sell electricity back to the grid, am just thinking if it makes sense to combine the following:

• Tesla Powerwall 2 or similiar
• Wholesale Electricity Price
• Probably a smart meter or smart home that allows one to charge the battery when the cost of electricity is below 30%-50% of the daily fluctuation average, and sell it when its above 30%-50%?... even an off peak hour charging and peak hour selling might make sense too?
• What would the ROI be like?

Potentially thinking this might

• Further mitigate the erratic fluctuations of Wholesale Electricity Price
• Possibly make some money from the selling of electricity to pay for the installation and powerwall
• Something that can be done in a HDB/apartment unit, since solar panels are not allowed