Rooftop solar and an 80 kWh battery for St Andrews Office Park (Block A)

The park buys its electricity from Ekurhuleni on a business tariff that charges for energy and for peak demand. From 1 July 2026, high-season energy costs R5.03/kWh, about double the low-season rate of R2.47/kWh.

An annual consumption figure tells you how much power a building uses and nothing about when. So we put loggers on site. On weekdays, demand climbs from about 8 kW at dawn to a peak of around 23 kW mid-afternoon, with a smaller rise in the early evening. On weekends it sits flat at 6 to 7 kW.

That gap was the design problem. An array sized for weekday demand makes far more than the buildings can use on a Saturday. One sized for the weekend barely touches the weekday bill.

We designed from the logged load and six months of municipal bills. The roof carries 108 Astronergy 620 W bifacial modules, 66.96 kWp in total, feeding a single WEG 60 kW three-phase hybrid inverter. Five 16 kWh WEG battery modules give 80 kWh of storage.

The battery earns its place twice. On weekdays it shaves the afternoon peak, which keeps the demand charge down. On weekends it stores the solar that the quiet buildings can’t use and releases it overnight, so less of the array’s output goes to waste.

It also holds at least four hours of backup for outages. If the park’s needs grow, more battery modules can be added later.

Work started on site on 25 August 2026 and the system was commissioned on 12 September. We handed it over to the Body Corporate on 6 October.

Our model projects that the system will cover about 77% of the park’s energy needs and cut its municipal bill by around 41%. That works out to roughly R276k off the bill in the first year and R3.9M over ten years.

Those savings land on common property costs, which the Body Corporate can pass on to owners and tenants.