Geyser Size Calculator — South Africa
Calculate the correct geyser capacity for your household using the standard SA sizing convention, SANS 10254 compliant. Compares running costs for electric, heat pump and solar geysers.
Quick answer: The standard SA industry rule of thumb is 50 litres per person for standard household usage, so a family of 4 needs a 200-litre geyser. High-usage households with double showers or bathtubs should increase to 60–70 litres per person. Heat pump geysers have a slower recovery rate for the same capacity.
Geyser Size Calculator
South Africa
For planning purposes only. All geyser installations in SA must be done by a registered plumber. A Compliance Certificate is required under SANS 10254 and SANS 10252.
How to Use This Calculator
- Enter number of occupantsThe number of people living in the property. The standard SA industry rule of thumb uses 50 litres per person as the basis.
- Select usage profileMedium, 50L per person, is the standard default. Choose Low for minimal showers or High for baths and double showers.
- Select geyser typeElectric is cheapest to buy. Heat pump and solar cost more upfront but far less to run.
- Enter electricity tariffCheck your municipal bill for your rate in R/kWh, used for the running-cost comparison.
- Click Calculate Geyser SizeResults show the recommended capacity, element size, recovery time and a running-cost comparison across all three geyser types.
Geyser Sizing in South Africa
The water heating system is typically the single largest electricity consumer in a South African home — accounting for 30–40% of the total electricity bill. Selecting the right geyser size and type is one of the highest-impact decisions a homeowner or property investor can make for energy efficiency and running cost reduction.
Geyser sizing itself follows standard SA industry convention rather than a fixed SANS table: the base calculation is simple, 50 litres of stored hot water per person per day for medium usage. This ensures the geyser can meet peak morning demand without running cold before everyone has showered. Installation and safety requirements are governed separately by SANS 10254 (The installation, maintenance, replacement and repair of fixed electric storage water heating systems), law since 2001.
Standard Geyser Sizes Available in South Africa
| Capacity | Occupants | Element | Recovery Time | Approx Price (2026) |
|---|---|---|---|---|
| 100L | 1–2 people | 2kW | ~2.5h | R1,800–R3,500 |
| 150L | 2–3 people | 3kW | ~2.5h | R2,200–R4,500 |
| 200L | 3–4 people | 3kW–4kW | ~3h | R2,800–R5,500 |
| 250L | 4–5 people | 4kW | ~3h | R3,500–R7,000 |
| 300L | 5–6 people | 4kW | ~3.5h | R4,500–R9,000 |
Electric vs Heat Pump vs Solar Geyser
South Africa's load shedding environment and high electricity tariffs have made geyser type selection more important than ever. Here is the practical comparison for SA conditions:
- Electric resistance geyser: Cheapest to install (R2,000–R5,000 + installation). 100% efficient — converts all electricity to heat. Most affected by load shedding. Highest running cost.
- Heat pump geyser: Higher purchase cost (R8,000–R20,000 + installation) but 60–70% cheaper to run. COP of 2.5–3.5 — produces 2.5–3.5 kWh of heat per kWh of electricity. Continues working during load shedding if powered by inverter/battery. Highly effective in SA's warm climate year-round.
- Solar geyser (thermosiphon or flat plate): Uses the sun directly to heat water. No electricity for heating in sunny weather. Requires electric backup element for cloudy days and winter. Pays back in 3–5 years in most SA locations. Not affected by load shedding for daytime use.
Geyser Placement and Installation Requirements
SANS 10254 specifies that electric geysers must be installed in an accessible location with adequate clearance for maintenance, fitted with a drip tray and drain pipe and connected to a dedicated circuit with the correct breaker rating. Most South African municipalities and insurers require a drip tray with an overflow pipe draining to outside the building — an overflowing geyser without a tray causes ceiling and structural damage that is not always covered by home insurance if the tray was absent. All geyser installations must be certified by a registered plumber who issues a Certificate of Compliance (CoC).
Geyser placement affects energy consumption significantly. A geyser installed close to the most-used hot water points loses less heat in the pipe run between the geyser and the outlet. Long pipe runs mean the hot water standing in the pipe cools between uses, wasting the energy used to heat it. Locating the geyser centrally between the major hot water points reduces standing losses meaningfully over the installation's lifetime.
Geyser Timers and Smart Controllers
A geyser timer is one of the lowest-cost energy-saving devices for South African homeowners, with payback periods under 12 months in most cases. A basic mechanical timer costs R200–R500 and restricts heating to off-peak hours. Smart geyser controllers (R800–R2,500) allow remote control, load shedding scheduling and solar integration. For households on time-of-use tariffs, restricting geyser operation to off-peak hours produces the largest savings. A geyser blanket (R200–R500) reduces standing heat losses by up to 30% on older uninsulated geysers and is one of the simplest energy-saving retrofits available. Newer geysers manufactured after approximately 2015 are factory-insulated to SANS standards and do not benefit significantly from an additional blanket. If your geyser is less than 10 years old, the blanket is unlikely to pay back its cost. On an older, uninsulated geyser — identified by a warm or hot exterior casing — the blanket is one of the highest return-on-investment energy interventions available to South African homeowners. Health guidance for domestic hot water systems recommends geyser thermostats be set to a minimum of 55°C to prevent Legionella growth and a maximum of 70°C for safety. The factory default of 65°C sits comfortably within this range. Heat pump geysers operating at SANS-compliant temperatures produce water at 55–60°C using 60–70% less electricity than a standard element geyser, making them the most energy-efficient option for households with consistent hot water demand above 200 litres per day.
Frequently Asked Questions
The standard SA industry rule of thumb is 50 litres per person for standard usage. A household of 4 people needs a 200-litre geyser. For high-usage households with double showers or bathtubs, increase to 60–70 litres per person. Heat pump geysers have a slower recovery rate and are typically sized at 150–200% of the equivalent electric geyser capacity — so a 4-person household would need a 300–400 litre heat pump unit.
A standard electric geyser uses a resistance element to heat water — it is 100% efficient, converting all electricity to heat. A heat pump geyser moves heat from the surrounding air into the water using a refrigeration cycle — it achieves 250–350% efficiency (COP of 2.5–3.5), meaning 1kW of electricity produces 2.5–3.5kW of heat. Heat pump geysers cost 60–70% less to run but cost more to buy (R8,000–R20,000 vs R2,000–R5,000 for electric). In South Africa's climate, heat pumps are highly effective year-round.
Yes, for electric geysers — a geyser blanket reduces standby heat loss by 25–40%, saving R200–R500 per year on electricity. This is especially effective for geysers in uninsulated roof spaces where ambient temperature fluctuates. Heat pump geysers already have superior insulation and benefit less from blankets. A geyser timer in combination with a blanket can reduce consumption by 30–40% with minimal investment.
SANS 10254 (The installation, maintenance, replacement and repair of fixed electric storage water heating systems) specifies minimum requirements for geyser installation, pressure control valves, drip trays and venting in South African buildings, and is law under Government Regulation No. 7079. Under SANS 10254 and SANS 10252, all new geyser installations and replacements must be done by a registered plumber. The installation must be inspected and a Compliance Certificate issued — this is required for insurance purposes and property sales.
A standard 150-litre electric geyser (3kW element) in a 4-person household typically consumes 4–6 kWh per day, costing R11–R17 per day at 2026 Eskom tariffs of approximately R2.80/kWh. That is R340–R500 per month just for the geyser. A heat pump running the same geyser would consume 1.5–2 kWh per day — saving R170–R380 per month. Solar geysers with electric backup use 1–2 kWh/day in summer, more in winter.
A well-insulated 150–200 litre geyser loses approximately 1–2°C per hour of standing. After a 2-hour load shedding slot, the water temperature drops from 60°C to 56–58°C — still hot enough for showers. After a 4-hour slot, the temperature is 52–56°C — still usable. Problems occur with multiple back-to-back slots (Stage 6) where the geyser never fully recovers between heating cycles. A geyser timer set to heat during off-peak windows between load shedding slots helps considerably.
A standard electric geyser in South Africa lasts 8–12 years, depending on water quality, pressure and maintenance. Hard water areas (much of Gauteng, the Karoo and parts of the Western Cape) cause faster scale build-up on the element and tank lining, shortening lifespan. Warning signs of an ageing geyser include rust-coloured water, a banging or popping noise during heating (scale falling off the element), reduced hot water capacity and the safety valve dripping more frequently. Replacing a geyser before it bursts avoids significant water damage — many insurers also note the geyser's age when assessing burst-geyser claims, and some decline claims on units well past their expected service life. A sacrificial anode replacement every 3–5 years can extend tank life considerably.
A 150L geyser suits a family of 3. A 200L geyser suits 4–5 people or high-use households. A larger geyser costs R500–R1,500 more to purchase but uses the same energy to heat a full tank — meaning you may run out of hot water less often, requiring fewer top-up heating cycles.
A standard 3kW geyser element heating a 150L tank from cold to 60°C uses approximately 7–10kWh. At R2.80/kWh (typical Eskom rate 2026), this costs R20–R28 per full heat cycle. A typical household's geyser contributes 35–40% of the monthly electricity bill — making insulation and solar geysers highly cost-effective.