Heating your geyser for less: The hidden costs of solar thermal and heat pumps systems

This year South Africans are bracing for electricity hikes of up to 25%, this means your geyser – the biggest electricity guzzler in your home - is going to cost 25% more to run.

What’s more the National Energy Regulator of South Africa (NERSA) is planning to target grid-tied solar users, driving the cost of electricity used at night peak times up and effectively destroying the business case for installing solar PV (electricity), unless you’re totally off the grid.

Geysers generally make up 40% of a household’s electricity bill. Until recently solar thermal (hot water) systems and heat pumps have been the main technologies available to consumers to keep these heating costs down. Although these systems are effective and can save you between 50% and 70% on hot water costs, these savings drop off significantly during winter when daylight hours are shorter and the sun’s lower trajectory means the panels are less effective. 

Solar Thermal systems use solar thermal (heat) energy to heat water, producing - it is commonly believed - about 70% of the energy required to heat the water. However, this assumes that your geyser is big enough to store enough hot water for evening and morning use, which is often not the case as most homes have a 150L or 200L geyser. With a bath typically using 100l of hot water and a shower 50l, a typical geyser will not store enough hot water for a family of four. This means your standard geyser element is working every night to “top-up” the solar geyser for morning use, reducing the proportion heated by the sun. This even more so in winter. A poorly maintained, pumped solar thermal system can actually cost you more money if it is pumping the heat back into the atmosphere. 

There can also be expensive services and maintenance costs associated with solar systems that must be considered, and that extend the payback period of your system. Should the pump in your solar system fail, replacing it costs about R1650. Replacing blocked-up non-return valves, cost R750. Replacing TP and PRV valves, cost up to R1250. These costs add up. 

Heat Pumps claim 67% efficiency, but did you know that this is based on an ambient temperature of 21 degrees? When the temperature drops below this, which it regularly does especially in winter, the energy efficiency of the heat pump also drops. The actual saving depends on the specific environment and condition of the heat pump. There are also the annual servicing costs (R950) to consider, and since heat pumps are made of many moving electrical parts these may sometimes need replacing. Here are some examples: replacing PC Boards, cost up to R2850; replacing compressors, cost up to R6500; refilling the refrigerant gas cost R3500. 

Although there are definite benefits to implementing these energy-savings systems, it’s important to know about these hidden costs, and to ensure that your system is as efficient as possible. Installing a long-lasting ceramic element in your geyser (like an Xtend Element) will reduce heating costs by 25% over the life of the element, increasing the efficiency of your solar system or heat pump. At between R3000 to R4000 to install, a ceramic element has the lowest approximate installation cost and quickest payback time of anything available on the market. 

These ceramic elements, protected by a stainless steel tube, turn your geyser into a thermal battery, storing the power generated in the day to use as hot water later. It works well with Solar PV systems as they produce more energy in the middle of the day (for free, from the sun), when demand is usually at its lowest. This results in the solar system throttling down (reducing production to meet the decreased demand). With a ceramic element, your geyser will store this heat from the sun and keep the water hot until you need it in the evening peak times.