ENERGY
T
his steep and sustained rise in electricity prices, combined with rising concerns about the health and environmental impacts of South Africa’s “dirty” coal-fired electricity, has prompted a country-wide search for ways to reduce our dependence on the grid. Water heating is the single biggest energy consumer in South African households at 40% of total household energy use ref. That makes it an obvious target for reducing the electricity bill. South Africa’s National Building Regulations prescribe minimum energy efficiency standards (through Regulation XA), which requires all new residential properties to derive at least 50% of the annual household water heating requirement from an energy source other than grid electricity.
THE WATER HEATING OPTIONS • Solar PV (photovoltaic) • Solar thermal (also known as solar geysers) • Heat pumps • Natural gas or liquefied petroleum gas (LPG) • Biomass • PV thermal (PVT) – a mix of solar PV and solar thermal
Water heating options.
WHICH IS BEST?
As with most things in life, the answer depends on individual priorities and circumstances. Factors such as location and climate, size of household, budget, reliability of electricity supply and importance of environmental considerations all have an impact on the suitability of available water heating options. However, there are clear advantages to some possibilities over others. Let’s first look at cost. When considering the cost of any system, it is important to factor in total lifetime cost. This includes the upfront cost of the system and installation (capital cost), as well as any ongoing expenses, such as electricity, and maintenance or repair outlays. The lifetime of the system is also a mitigating aspect. There is a methodology to account for all the above factors called levelised cost of energy (LCOE). It calculates the total cost per unit of energy (called a kWh or “kilowatt-hour”) for various energy options. The graph on the right shows the overall cost or LCOE for several water heating options in South Africa as at 2021 (see tab “levelised cost of energy” at ref). The graph clarifies that solar PV and solar thermal water heating are by far the lowest cost options for heating water. The most expensive option is, as anticipated, electricity from Eskom or the municipality.
Water heating is the single biggest energy consumer in South African households at 40% of total household energy use. Range of Eskom and municipal residential electricity tariffs 2021-22
Overall cost* for residential water heating (R/kWh).
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