Geyser · break-even
Heat pump or solar geyser — when does it pay?
Hot water is about 40% of a South African electricity bill. Pick a heat pump or a solar geyser, put in the quote, and see the year the savings over an electric geyser cover the cost.
How we calculate it
- What an electric geyser uses comes first — the litres of hot water a day heated from 20 °C mains to 60 °C (4.186 kJ a litre a degree), plus the heat the tank loses standing (0.012 kWh a litre a day).
- A heat pump uses 1/COP of that — at a COP of 3 it uses a third of the electricity for the same hot water.
- A solar geyser lets the sun do part of the heating; the element covers the rest (cloudy days, winter).
- Year 0 is the install cost, as a minus. If your old geyser has burst anyway, put in what a new electric one would cost — that part comes off.
- Each year saves the kWh you no longer buy x the price that year, rising by the increase you set. With a loan rate, interest runs while you are still behind.
- Rand as spent, not today’s money; servicing, repairs and a replacement are left out.
We calculate; we never name a product or an installer. Get more than one quote, and check the warranty on the tank and the compressor or collectors.
Where the typical figures come from
- Hot water is about 40% of a household bill (34–41% for an Eskom Homepower 4 user). BusinessTech.
- Install prices (2026): heat pump R27 500–R44 500 (100–150 L), R39 500–R53 500 (200 L), R44 500–R59 500 (250–300 L); solar geyser R22 500–R29 500 (100 L), R25 500–R34 500 (150 L), R29 500–R42 500 (200 L), R32 000–R50 000 (300 L); an electric geyser R4 800–R14 500. The presets use about the middle. EnergyBee heat pumps, 2026, EnergyBee solar geysers, 2026.
- Heat pump COP 3.0–4.5 (EnergyBee); we start at 3.0 for a South African winter. Solar geyser 60%: Eskom’s calculator assumes “a saving of approximately 60%” for a solar geyser or a heat pump, and 20 °C mains water; a study across 43 African countries found 25–88% for evacuated tubes, depending on the region. Eskom calculator assumptions, AGRIS / FAO.
- Hot water and tank size: about 50 L a person a day (Eskom’s calculator uses 80 L an adult); 100–150 L for 1–3 people, 200 L for 3–4, 250–300 L for 5+. SANS 151 allows up to 2.5 kWh a day standing loss on a 150 L tank. Kwikot sizing guide, Kwikot electric geyser guide.
- Price increases — Low 6%, Moderate 9%, High 13%: the same NERSA figures as our solar calculator. Engineering News, 2026.
- Our estimates, not sourced: the standing loss for tank sizes other than 150 L, the 60 °C setting and the hot water in each preset. Use your own quote and your own household.