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How to participate
- The claim form
- Choosing a supplier and a system
- Contacting the Help Desk
- Choosing the right solar water heating system
- Criteria for systems to qualify for a rebate
- The Supplier
- The Installer
- How does solar water heating work?
- Types of solar water heating systems
- Types of solar collectors
- Different ways solar water heaters circulate your water
- Using the timer
- Installation tips
- Usage tips
- Selecting the right size solar water heating system
- Saving with a solar water heating system
- Environmental benefits
- Post installation requirements
When purchasing an approved system from a registered Eskom supplier consumers will be provided with a claim form. The form needs to be completed by the supplier and consumer. Details on where and how to forward claims are included on the claim form. The rebate is paid within 8 weeks of submission of the form
The amount of rebate your system qualifies for depends on how much electricity the system will displace. For cost, installation and rebate values go to The Supplier page.
- Look on The Supplier page to see which suppliers and products are registered with the programme.
- Contact suppliers in your area
- Have them recommend a system to you, based on your home, family size, usage pattern, location and budget.
- Confirm that the system you choose will qualify for a rebate, as not all systems being sold by suppliers will.
- Follow the normal sales procedure with your chosen supplier.
- Ensure your old electric geyser is disabled.
- Complete and sign required documentation.
- Submit required forms in the supplied envelope to the facilitating auditors.
- You will receive SMS progress reports on your claim.
Click here to go to The Supplier page with all registered supplier detailsE-mail us: solar@eskom.co.za
Phone us: 011 800 4744
Choosing the right solar water heating system
Before making a decision on purchasing a system, Eskom recommends that you familiarise yourself with the options that are available through registered suppliers. Before installing we recommend that you either call our DSM Helpdesk or check the latest list to confirm that the proposed installation qualifies for a rebate.
Criteria for systems to qualify for a rebate
Only registered products, complying with the following criteria, qualify for the rebate:
- The system must have passed the South African Bureau of Standards (SABS) tests, and comply with the South African National Standards (SANS) for thermal and mechanical performance and safety.
- It must be a high-pressure system with pressure higher than 100kPa.
- The system must have a timer to optimise energy savings and regulate everyday usage. Alternatively, a load management device, i.e. a geyser buddy or ripple relay, to control the usage in crisis situations must be installed.
- The system must be appropriate for the household and area in which it is installed, in terms of size, frost protection and water quality compatibility.
- It must have a comprehensive guarantee of at least five years.
- The supplier of the system must be registered with SESSA (Sustainable Energy Society of South Africa) solar water heating division.
- The system must be installed by a registered installer and the customer will only be able to claim the rebate once facilitating auditors receive a final invoice from their supplier.
All suppliers and installers participating in the solar water heating programme have voluntarily registered themselves and their systems, the process having been managed by an independent auditing firm. The types of systems tested and sold depends entirely on the supplier.
• List of registered suppliers and products
- Breakdown of SABS
- SABS Test Certificate
In order to be part of the Eskom Solar programme, suppliers are required to have their systems tested and passed according to SABS standards. Systems that do not pass the SABS test will not be allowed to be part of the programme up until such time that they can pass the complete test. A test certificate for a system is valid for 1 year.The test certificate serves only as an indication of the quality of the system, it does not constitute SABS Mark approval.- SABS Mark Approval
SABS Product Certification Mark approval is a voluntary scheme that entails a test report to be submitted to the approvals board and an audit of the quality system at the applicant‘s manufacturing factory (e.g. ISO 9001).
To maintain SABS Mark approval acceptance, manufacturers have to submit samples for subsequent testing to demonstrate ongoing acceptance and conformance to the relevant specifications.Note: SABS test report
A test report relates only to the specific sample(s) tested as identified there in. It does not imply SABS Mark approval of the quality and/or performance of the item(s) in question and the test results do not apply to any similar item that has not been tested.
SABS Mark approval gives a vastly better assurance of quality products, and consumers should bear this in mind when making a decision about the price and longevity of products. SABS approval for solar water heating systems is not currently common in South Africa but is being pursued and more suppliers are expected to become SABS Mark holders.
Note: The programme does not stipulate what systems suppliers have tested.
The suppliers are fully responsible for their own installation teams, and you are advised to liaise directly with the suppliers in this regard.
How does solar water heating work?
A solar water heater is a combination of three elements:
- Solar collector - an energy device, designed to absorb solar radiation and transfer the energy to the energy transfer fluid or material passing through the collector.
- Energy transfer medium - a medium that through the process of conduction or convection, transfers the absorbed heat to the water. The type of material used is dependant on the design and needs of the installation. Where freezing of the transfer medium is a concern, the liquid used should be mixed with a non-toxic coloured anti-freeze liquid and a corrosion inhibitor.
- A thermally insulated hot water storage vessel or geyser with a protected inner lining, copper, steel or a polymer. There are solar water heating systems that work on a low pressure, but most are pressurised from 100 kPa to 600 kPa, depending on the materials used. (The Eskom programme will initially only rebate high pressure systems)
Solar water system tanks/storage vessels should normally be larger than conventional household geysers. This is because the sun is heating the total volume of hot water that is required for the day. For your conventional 150 litre electric geyser to heat 300 litres it will need to cycle and heat the extra body of water.
Solar water heaters can be plumbed in series to pre-feed your existing geysers, or can completely replace existing geysers. The complete system can be mounted on top of the roof, if the structure can hold the mass, or the hot water storage vessel can be mounted under the roof at a high level or at ground level in a utility room or cupboard. Solar water geysers/storage vessels function best when mounted vertically. However if there are physical or aesthetic concerns the geyser can be mounted horizontally.
Types of solar water heating systems
There are two broad types of solar water heating systems:
- Open circuit or direct systems circulate water directly from the collectors to the tank/cylinder. These types of systems are not normally freeze resistant or resistant to hard or corrosive water.
Rebates will not be paid for direct systems installed inland where frost occurs unless the SABS proves them to be frost resistant according to the standards.
- Closed-circuit or indirect systems contain a heat exchanger, normally a fluid which is held inside a piping system and solar collector panel where it is heated by the sun. This fluid is circulated through the piping system to the hot water cylinder/tank where the heat from the fluid is transferred to the water. The cooled fluid is then returned to the collector for reheating.
Closed circuit / indirect systems should be used in areas that get frost (temperatures below 4 ºC) or have water with a high mineral content (hard water), as they are not affected by these characteristics.
There are two main types of solar collectors:
- Flat-plate collectors
- Vacuum (Heat pipe) / Evacuated tubes
There are various ways in which these two systems can work effectively for you. We suggest you look at the two types to understand the different ways they can function and for what reasons. Your selection should be based on a combination of factors that can give you and your specific needs the best possible performance and value for money.
Both variants are available in direct and indirect, pumped and thermosiphon applications. (Link to this page). Further, they be can be installed in a pre-heat (link to pre-heat section) configuration, where you make use of your existing geyser.
1. Flat collectors have a good price-performance ratio, as well as a broad range of mounting possibilities (on the roof, in the roof itself, or unattached).
Fig 1: Example of a flat-plate collector
A flat-plate collector has the following features:
- A cover (glazing), usually made of toughened glass.
- An absorber plate, coated with a high absorption and low emissive layer of black high-temperature paint or special selective coating.
- A tube system made of the same or a similar material as the absorber plate itself that removes the absorbed heat to the tank.
- A casing that is both non-corrosive and waterproof. Insulation is needed on the back and sides to assist in maintaining the absorbed heat.
2. Vacuum tube (heat pipe) / Evacuated tube collectors
Vacuum tube collectors have the following characteristics:
The collector in this type of system is located in individual glass tubes.
- These tubes are rigged in parallel with one another to make up the collector.
- When the tubes are exposed to high temperatures, the air inside them is forced out or ‘evacuated'. This evacuation of the air creates a vacuum effect and it is this vacuum effect that makes the tubes good insulators. In plain English, this vacuum effect keeps the heat (hot water) inside the tube, while leaving the outside cool.
- Heat pipes have a single layer of glass whereas evacuated tubes have a double layer of glass.
- Heat pipes and evacuated tube collectors both contain a special fluid which begins to vaporise at low temperatures. The steam rises in the individual tubes and warms up the water in the main pipe by means of a heat exchanger. The condensed liquid then flows back into the base of the heat pipe.
Fig2: Example of an evacuated tube collector
Evacuated tubes work in much the same way as your electric geyser in terms of overflow. A safety valve opens to let out hot water when the pressure is too high. If your system is not installed with extra piping to channel this water away, it will run down your roof. Though this is not a big issue, after a while you could see white streaks on your roof due to chemical build up. If you are concerned about this, we recommend that you speak to your supplier to advise you further.
Different ways solar water heaters circulate your water
Water can be moved around the solar heating system in one of two ways:
a. Forced circulation / Pumped system
The system works with a small circulation pump, controlled by a temperature differential controller, which circulates the heat transfer fluid from the collectors to the heat exchanger in the solar geyser. Collectors are mounted outside on the roof, with the solar geyser installed in a space provided.Pumped systems can be more expensive than natural convection systems due to the added technology, particularly if antifreeze measures are required. However, they can be the right solution if your roof structure and support beams (trusses) cannot support the weight of the solar water tank. If the pumps performance is maximised then your systems operation and savings will be maximised.
A temperature differential controller is used to control the pump:
- This differential controller switches on the pump when the correct temperature is detected at the hot water outlet (the controller will only allow water to be released once the water in the collector is higher than that stored in the storage vessel/water tank at any given time).
- The differential controller therefore also switches the pump off when the fluid in the collectors is within 50C of the return temperature's cold probe from the solar geyser.
The pumps in forced circulation systems have low power requirements. Direct current (DC) pumps powered by small photovoltaic (PV) panels which convert sunlight into DC electricity are sometimes used. Although, care needs to be taken here as photovoltaic technology works on light received and not heat.
Should a photovoltaic pump be used, emphasis should be made not to control the pump using panel voltage. A differential temperature controller must be included.
This will ensure the system is not cooled in the late afternoon when there is sufficient light to run the pump but insufficient solar radiation to heat the water.Advantage: if you are concerned about aesthetics, you will not need to place the system on your roof.
Disadvantage: unless you use photovoltaic technology to power the pump, if there is no electricity you will not have hot water.All geysers taking part in this programme with electrical backup will use timers in order to maximise savings. The use of a timer has being proven to be the most efficient way to use a solar water heater in South Africa. (Please link to 4.7)
b. Natural convection / Thermosiphon system
Thermosiphon systems work with the natural laws of circulation - hot water rises and cold water sinks.
As the water in the collector is heated, it rises naturally into the geyser, while the cooler, heavier water in the geyser flows down to the bottom of the collector, causing circulation through the system. To achieve circulation during the day and to limit reverse circulation at night, the water tank/cylinder must be above the collector.Thermosiphon systems can be freeze-resistant. Anti-freeze valves and built-in freeze resistance can be used by placing a closed circuit between the collector and the geyser. This means a heat transfer fluid will be used.
Natural convection systems are mainly used in houses where the water tank can be installed at a higher level than the collector, either inside or on top of the roof. This type of system works best if installed in houses with roofs pitched higher than 15º. Roofs with a lower pitch will still work, however the overall effectiveness will just be decreased although additional inclined support frames can be supplied.
Typical thermosiphon installations use a close-couple configuration. This means the solar water tank and the collector will be in close proximity to each other, with the solar tank higher than the collector.
The tank can be placed inside your roof, as long as it remains above the level of the collector.Thermosiphon systems can be either close-couple or split systems.
- In a close-couple system, the solar geyser and collector are mounted externally and close together. In thermosiphon circulation a close-couple system is very reliable if installed properly.
- In a split thermosiphon system the solar geyser and collector are separated with the geyser usually installed in the roof. The geyser must be above the collector with connecting pipes rising smoothly. The pipes should not level out or dip at any point, as this could cause poor circulation.
Advantage:
- you do not need any power source to get hot water: systems are reliable and simple
- you will maximise your energy savings.
When solar water heating systems do not use timers, they rely on thermostats to control when the element switches on and off. This is not an efficient or cost-effective way to operate the system.
Say for instance, you use your hot water in the morning for whatever purpose. If you do not have a timer, the thermostat will automatically come on to heat your water. BUT, this is not practical as this is when the sun will also start to heat your water. Therefore if you do not have a timer or it is not programmed properly, you will not save money as you will use both electricity and solar energy to heat your water until it reaches the set temperature.
A note to remember is that an electrical element can heat the water in about an hour and a half whereas the sun takes longer, but is free.
The greater savings made by using a timer has been proven through a monitoring initiative around the country.
An override function must be provided on all systems installed with timers, but we implore customers to use this only when strictly necessary.
This will save you the optimum amount of electricity and provide the necessary reduction in peak-period use.
The timers will be set to bring the element on from 4 am to 6 am and then again from 4 pm to 6 pm. This will ensure that if there was not sufficient energy during the day to heat your water, you will still have hot water in the evening and early morning.
If customers wish to set the timers differently, they should discuss this with the supplier. However, they must not come on during peak electricity use periods.
Timers do have battery back-up to withstand power outages. Customers should however check that their timers keep good time to ensure optimum performance.
Many solar-heated water consumers will eventually turn the back-up option off completely once they get used to the system. This is also the fastest way to reduce the system's payback period.
Please note that for pre-heat/feed systems this is not feasible as the electric element assists with the standing heat losses that occur due to the lesser insulation abilities of a conventional electric geyser. It is highly recommended that if one takes this route you also insulate your electric geyser with a geyser blanket to reduce your heat/energy losses.
Select the right system for your geographical area.
- There are direct systems that are freeze-tolerant and you must ensure that if you live in an area that gets frost, you must purchase a freeze-tolerant system. Non-freeze tolerant systems should NOT be installed in areas that have winter temperatures lower than 4 ºC and also not in areas with extremely hard or soft water, as lime scale and calcification will occur inside the collector.
- In areas that get frost, freeze-tolerant systems are the way to go. But if you have hard water, you ought to select an indirect system.
- Correct collector orientation and inclination are imperative when installing a solar water heater. Collectors should face true north in the southern hemisphere or, as an alternative, slightly west rather than east, because of the higher ambient temperatures in the afternoon. A deviation of 45º east or west will have no major effect on the collector's efficiency. However, deviations greater than this will require extra square metres of collectors to compensate for losses of solar energy.
- The rule of thumb for pitching the collectors is latitude +10º. This orientation will give you maximum value for sun throughout the year. It is important to note that evacuated tube collectors depend less on orientation than flat-plate collectors.
- If your home does not allow for this orientation the system will still work so long as it receives direct sunlight. Your efficiency and temperature of the water will however be reduced. Additional inclined support could be used
Remember: the sun rises in the east and sets in the west
- Keep shade in mind when deciding where to install the solar collectors. If an area is in shade between 09:00 and 15:00, another position should be found. A simple rule to keep in mind is to position the solar collector at a distance away from the obstacle, that is equal to twice the actual height of the obstacle. This is true for areas of higher latitudes such as Cape Town. For Johannesburg and lower latitudes, the distance can be reduced to approximately one and a half times the size of the object.Partial shading (for example by chimneys and TV antennas) on buildings during sunshine hours is acceptable, provided it does not exceed 10% of the area.
- Solar collectors have to be clean to be as effective as possible. In extremely dusty areas or areas subject to dust or sand storms, the glass panel of the collectors should be washed with clean water once a month to ensure optimum absorption. Adequate rainfall may clean the glass panel naturally.
- Evacuated tube systems may require re-evacuation a couple of times during the system's expected lifetime. Please consult your supplier for maintenance requirements.
- Indirect systems require the heat transfer fluid to be changed on average once every 6 years.
- A solar water heater with an element that works on an automatic thermostat cannot save electricity to its full potential. If a substantial part of the overall volume is consumed in the early morning or the late evening, the element will want to heat the water up immediately, even though there is sufficient solar radiation available to do so. Timers should be fitted where automatic and not manual back-up is required. Maximum savings will only be achieved by either switching off the element or timing it out automatically. An override function will be incorporated in a situation where you know the solar water system will not be able to cope; such as a larger number of people needing to shower. Therefore you can rent rooms out to fans of the 2010 World Cup and still provide enough hot water for them!
- Savings can be further maximised by using hot water in the evening rather than in the morning, for example by showering or bathing before going to bed instead of after getting up. This way you maximise the free energy saved during the day.
- To optimise energy and hot water savings, install energy and water saving shower heads and aerators in taps to reduce hot water consumption.
- Insulate hot water piping to minimise heat losses and reduce the requirement for electrical back-up power. Consult your supplier about insulation suitable for solar water heating - the average insulation can become porous and corrode quickly as it cannot handle the high temperatures of solar heated water.
- Showering generally uses less water than bathing.
- Use cold water to wash hands and rinse glasses. This way the system will not need to reheat unnecessarily.
- For health reasons your hot water system should provide water at above 55ºC and ideally be around 60ºC.
Remember that effective solar water heating and energy saving is achieved by the correct and clever use of our resources. We need to become responsible energy users, both for the environment and our pockets!
Selecting the right size solar water heating system
Sizing a solar water heating system involves determining the total collector area and the storage volume required to provide 100% of the household's hot water needs. It is extremely important to select the right size geyser and collectors to install.
When sizing a solar water heater system, a rule of thumb is to allow at least 50 litres of water at a minimum of 55 º C and preferably 60 º C per person per day. However, the household's specific consumption patterns should be taken into account. The following example shows how to size a solar system:
Sizing example for a household of four people:
Daily hot water requirement 50 litres per person (200 litres) Hand basins 5 litres per person per day (20 litres) Dishwashing 3 litres per meal, assume 2 meals at home daily (24 litres) Add compensation for heat loss due to cold water mixing 244 litres x 20% (48.8 litres) No washing machine added - Total hot water requirement 292.8 litres per day Saving with a solar water heating system
- Savings can be maximised by using hot water in the evening rather than in the morning, for example by showering or bathing before going to bed instead of after getting up. This way you maximise the free energy saved during the day.
- To optimise energy and hot water savings, install energy and water saving shower heads and aerators in taps to reduce hot water consumption.
- Insulate hot water piping to minimise heat losses and reduce the requirement for electrical back-up power.
- Showering generally uses less water than bathing.
- Use cold water to wash hands and rinse glasses. This way the system will not need to reheat unnecessarily.
- For health reasons your hot water system should provide water at above 55ºC and ideally be around 60ºC.
Solar water heating benefits people and their pockets in two main ways.
Economically speaking, homeowners can make considerable savings on their electricity usage. Water heating accounts for 30% - 50% of the electricity consumed by an average household, and a solar system can reduce that figure by at least 70%, depending on the system selected.
In terms of the environment, the benefits are impressive. A 150 litre solar water heater will replace 4.5 kWh of electricity per day, resulting in the following environmental annual savings:
Savings per kWh¹ Approximate annual savings Water: 1.26 l/kWh 2.07 kilolitres Coal: 0.5 kg/kWh 821kg Ash: 0.28 g/kWh 460g SO2: 8.79 g/kWh 14.4kg NOx: 3.87 g/kWh 6.4kg CO2: 0.96 kg/kWh 1.6tonnes
¹ As obtained from Eskom Corporate TADBy installing a solar water heater, you will significantly reduce the volume of noxious emissions into the atmosphere. This means that you will personally be reducing the volume of harmful emissions that cause global warming!
Post installation requirements
- Technical auditors. A technical audit team will contact a selection of customers and set up a time to visit the home owner to check the installation. This process serves to verify that installations are done correctly and that customers received the system that they paid for.
- Measurement and verification (M&V)
- In order to provide the savings incentive to customers Eskom has to prove to NERSA (National Energy Regulator of South Africa) that there is a sustainable reduction in energy use.
- Therefore selected homes will be chosen to have a monitoring system fitted on their solar water heater. A database will be kept of the selected homes and you will be able to contact the call centre to confirm if you are on the list if you are approached.
Please note that this equipment will not affect your system.
The measurement and verification of the programme is in place to ensure, the programmes longevity and that people properly benefit from the programme. These checks are compulsory if you choose to take part in the programme.
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