Three Steps to Choosing the Perfect Gas Geyser When Upgrading

25 May 2026 Posted By admin

The cost of operating an electric water heater accounts for a significant portion of the electricity bill for households across South Africa. The increase in Eskom tariffs which rose 12.74% in 2024-25 and a further 12.7% in 2025-26 also contributed to this.

The result is that a number of households are upgrading to gas geysers which can operate independently of the grid. However, gas geysers are sized differently from electric ones. Getting the sizing wrong means cold showers in winter, fluctuating water temperatures, or a geyser working beyond its design capacity.

Here, we are going to outline three steps that simplify the process for you.

How Gas Geysers Differ from Electric Ones

Electric geysers heat stored water using a heating element. Unlike these, gas geysers are instantaneous, i.e., they heat water as it flow through. As a result, they are sized in litres per minute (L/min) which accounts for the volume of water the unit can heat to a set temperature rise every minute.

A standard gas geyser heats incoming water by approximately 25°C above ambient temperature at its rated flow rate. In winters, incoming mains water can be 10-12°C. This means a correctly sized unit must still deliver a comfortable 35-40°C at the shower head under those conditions.

An undersized geyser doesn’t just deliver lukewarm water. It can create pressure and temperature instability across water outlets.

The Three Steps to Choosing Your Gas Geyser Size

When choosing a gas geyser South Africa, these are the steps you need to follow:

Measure Your Flow Rate Using the Bucket Test

Your geyser must be sized to match your home’s water flow rate, not the water pressure. This is the volume of water that passes through your tap per minute, and is determined by both pressure and pipe diameter.

Perform the Bucket Test by placing a bucket of known volume under each hot water outlet, turning on the tap fully, and calculating how long it takes for the bucket to fill completely. If you have multiple outlets, run all of them at the same time and add the individual flow rates.

Table 1: Minimum geyser size as per household.

Always step up your geyser size when buying since cold water during winter can reduce the effective output of the geyser.

Choose the Right Geyser Model Type

Once you know the flow rate, the next step is to choose the geyser model type. In the South African market, the four main types available are:

Table 2: Gas geyser models available.

Deciding Between Indoor vs. Outdoor Installation

The placement of your geyser has a direct impact on which model is suitable, what compliance requirements apply, and what the installation will cost.

Table 3: Factors that influence indoor vs. outdoor installation.

What to Confirm With Your Installer before Purchasing the Geyser

Before choosing a gas geyser South Africa, speak to your installer and get a confirmation regarding the following:

• Flow rate of your outlets: Best to confirm this via bucket test before selecting geyser size.
• Cylinder size requirement: Check your current setup since fan-forced 20 L/min units need a minimum 48 kg cylinder.
• Pipe diameter and run length: The longer your pipe runs from geyser to outlets the larger is the diameter of the pipe required.
• Flue compatibility: Indoor installations require a flue routed to the outside. Thus, it is important to confirm wall penetration is feasible before buying.
• CoC from current installation: If you are replacing an existing gas geyser, the installer will have to assess whether existing pipework is compliant with SANS 10087-1:2024 before issuing a new CoC.

Wrapping Up

Choosing the right gas geyser is simpler when you have an SAQCC-registered installer working with you since the beginning. Start with doing the bucket test, choose the right geyser size based on your household requirements, and hire a certified installer for the installation and CoC.