How a Family of Three Reached 99% Solar Water Heating in Four Months

The Story

When Riaan and Anel Vermeulen moved into their Centurion townhouse in late 2024, the first bill that caught their eye was Eskom’s. Their 150-litre geyser was cycling through the night, drawing over 200 kWh of grid power each month just to keep water hot for a household of three. Riaan, an IT project manager who tracks everything in spreadsheets, decided the geyser was the lowest-hanging fruit.

They installed a 2.1 kWp solar-PV array on their north-facing roof in February 2025, wired directly to support their existing electric geyser — no gas conversion, no plumbing changes. The system went live on 11 March 2025.

The results were immediate and, frankly, hard to believe. Over the first four months of monitoring — which included Gauteng’s notoriously cold May and June — the system delivered 192 kWh of solar energy to the geyser per month while drawing just 1.4 kWh from the grid. That’s a 99% solar fraction. Their monthly grid cost for water heating dropped to R5.

Anel puts it simply: “I kept checking the meter because I thought it was broken. Five rand a month for hot water — for a family of three, through winter. We haven’t changed a single habit.”

Over the full monitoring window, the system accumulated 839 kWh of solar energy against just 6.1 kWh from the grid. The estimated total monthly saving — factoring in the avoided grid cost and the value of solar energy consumed — sits at R910 per month. At that rate, the system pays for itself well within two years.

The Vermeulen case is notable not just for the headline number but for what it proves: even through a Highveld winter, a modestly-sized PV array on a standard electric geyser can deliver near-total solar coverage with zero lifestyle disruption.