All solar PV systems installed within the City's electricity supply area must be authorised by us. See our useful guideline documents below:

• Requirements for Small-scale Embedded Generation
• Guidelines for Safe and Legal PV installation in Cape Town
• Registration is legally required in terms of the City of Cape Town Electricity Supply By-Law, 2010 and ensures the safety of anyone who comes into contact with the PV system or the grid itself.
• Apply for authorisation to install an embedded generation system

Solar photovoltaic (PV) systems, or solar power systems, are renewable energy systems that convert sunlight into electricity. The electricity they generate can be stored in batteries, used directly, or fed back into the electricity grid. Solar PV works well for a wide range of residential, industrial, commercial and agricultural uses and is considered clean as no fossil fuel is used in generating the electricity

PV technology produces electricity directly from the interaction of sunlight with certain semiconductor materials, such as silicon, in the PV module. The electrons freed during this interaction then flow as direct current (DC) electricity from the module. This electricity can be used as direct current or changed via an inverter to alternating current (AC) electricity which is the form that grid electricity is available to you in your home or business.

A solar PV system includes different components that should be selected according to the system type, site location and uses. The major components for solar PV systems are:

• PV module – converts sunlight into Direct Current (DC) electricity.
• Battery (optional) – stores energy from the PV modules to supply electricity when there is additional demand or when there is no sun.
• Solar charge controller (required for battery systems only) – regulates the voltage and current coming from the PV panels going to the battery, which prevents battery overcharging, and prolongs the battery life.
• Inverter – converts DC output of PV panels into AC current for use by normal household or office appliances, or to be fed back into the electrical grid.
• AC & DC switch gear – connects and disconnects the PV system from the appliance or equipment using electricity (called the “load”).
• Load – all the electrical appliances and equipment that are connected to a solar PV system such as lights, radio, TV, computer, refrigerator, etc.

Solar PV is not commonly used to heat water. There are various types of solar energy technologies with the same input (solar radiation), but differ in forms of energy output (electricity or heat).

Solar PV systems use PV panels to convert sunlight into electricity, which is used for various electrical appliances in the building. No water is involved with the functional operation of solar PV.

Solar water heaters or solar geysers use solar thermal energy to heat water directly by means of a set of pipes or collectors placed on the roof of your home. No electricity is generated, although an electrical element can be used as a backup when solar thermal energy is insufficient.

Some water heating systems do use solar PV panels to generate electricity from the sun to heat water via an electrical element. The water can then be used throughout your home for all your hot water needs. This technology is not widely used but is becoming increasingly popular.

PV panels or modules are the thinner ones, typically 2,5 to 5 cm thick with typically an array of 7,5 to 10 cm blue solar cells behind the cover glass. Solar water heating panels are generally much thicker, and may be connected to a water tank above it (the tank can also be inside the roof).

Technically it’s possible, with a large enough PV system, but it’s generally not cost- effective. PV systems are usually designed to provide electricity to run your lights, appliances and other electric devices in your home.

No, the electricity generated by your system is used directly by the appliances and equipment operating on your property when it is produced. Batteries are needed to store electricity.

PV systems run whenever the sun is shining. Batteries are only required if you want electricity when there are power outages from the grid, or if you want to be independent of the grid at night or when the sun is not shining. Batteries are still expensive, have a limited life (5-10 years being typical) and require maintenance. Battery backup is most commonly used in remote areas where there is no electric service (off-the-grid).

No electricity access during load-shedding:
It is unsafe to generate and supply your own solar PV power without being connected to an additional more stable power source (such as the utility grid or battery backup). As a result, a grid-connected solar PV installation will not provide electricity during load-shedding or other power outages. When the utility grid goes down, the solar PV inverter will automatically disconnect from the grid as a safety feature. This safety feature is known as anti-islanding and is important to keep the grid and your home appliances safe.

Some electricity access during load-shedding:
The exception to above is if you have a battery backup system, and are “grid-tied” (this is known as a grid-tied hybrid system). In this case, a suitably interlocked changeover switch on your electricity board can be activated to shift the house electricity demand from the grid to your batteries. You will then have electricity access to some of your home appliances, during load-shedding. The appliances with electricity access will depend on what is safely connected and the size of your hybrid system.
Note: It is important to have a suitably interlocked changeover switch installed, so request one because they are not ordinarily provided.

The modules are made of tempered glass and are very strong. They pass severe wind and hail tests, and are regularly installed in areas prone to hurricanes as well as Arctic and Antarctic conditions.

Inverter - A power device that converts direct current (DC) to alternating current (AC) at a certain voltage and frequency. This device allows battery stored or solar PV generated power to be converted into usable (the required voltage and frequency) AC power that can supply your home. It is important to distinguish between battery, solar and hybrid inverters when considering a solar PV, battery backup or hybrid system.

Solar Charge Controller - A solar charge controller or regulator regulates voltage and current generated by the PV panels to keep batteries from overcharging.

Direct Current (DC) - The flow of electrical current in one constant direction. Direct current is typically converted to alternating current for practical purposes, as most modern uses of electricity require alternating current. Solar PV panels generate direct current.

Alternating current (AC) - The flow of electrical energy that follows a sine wave and changes direction at a fixed frequency (i.e. it alternates). Most residential and commercial/industrial users of electricity require alternating current.

Power Utility - A power utility is responsible for the electricity grid infrastructure. Homes, businesses and other users connect to this grid to get electricity. In Cape Town both the City of Cape Town and Eskom are responsible for portions of the electricity distribution network within the City of Cape Town’s formal metropolitan boundaries.

Bi-directional Meter - A meter that measures the active energy (kWh) flow in both directions (import and export) and either displays the balance of the imported and exported energy in a single register meter (net metering) or displays both imported and exported energy in separate registers.

Anti-islanding - The ability of a small-scale embedded generation (SSEG) installation to instantly and automatically disconnect the generator from the distribution network whenever there is a power outage, thus preventing the export of electricity to the distribution network from the SSEG. This is done primarily to protect the distributor’s workers who may be working on the distribution network and who may be unaware that the network is still being energised by the generator.

Grid-tied SSEG - SSEG that is connected in parallel to the distribution network either directly or through a customer’s internal wiring is said to be grid-tied. SSEG that is connected to the grid through a reverse power flow blocking relay is also considered to be grid-tied.

Generation/Generating Capacity – refers to the total output capacity of the generator. For PV systems in particular, this refers to the maximum output of the solar PV inverter.

Solar Installed Capacity – This is how the maximum DC power of solar PV system is measured. Assuming the same type of panel is used, the Solar Installed Capacity can be found by multiplying the solar panel Wp rating with the amount of solar panels installed.

Yes, all grid tied PV systems must be approved by the City of Cape Town. The local electricity utility has rules and procedures that must be followed to connect PV or any generator to the grid safely and legally. In Cape Town, only installations connecting to the City’s electricity grid (and not Eskom’s) currently have the option to become grid-tied. See our guidelines for Safe and Legal PV installation in Cape Town.

A grid-tied system will require a new meter that reads electricity use in both directions (a bi-directional meter), and will also be required go onto a new Embedded Generation Tariff. If you do wish to be grid-tied, but not feed back into the grid, you will need to install a reverse power flow blocking relay. This will exempt you from installing a bi- directional meter and from going onto the embedded generation tariff. The City of Cape Town Electricity Generation & Distribution Department will help you with the documentation and procedures  and the requirements for SSEG document. The guideline document explaining how to connect to the grid is available on their website at: www.capetown.gov.za/ElecServiceForms and on the resources page.

If you have a system that generates more electricity than you use, then the excess can be sent back into the City of Cape Town’s power grid. Your new tariff agreement with the City will refund you for any excess electricity you generate.

Yes. In fact, many PV systems are designed as on-grid systems, meaning they are designed to interconnect with utility power and not use battery storage. As most people at this stage can only generate some of their electricity needs from solar, they still need to be connected to the grid. (E.g. because battery storage is expensive, electricity would still be needed during the day when the home needs more power than the solar PV can provide, and at night).

Yes, PV systems can be designed to provide power independently from the utility. These “off-grid” systems rely on batteries to store power for night times and when the PV panels are not generating as much as needed. (Note that sizing systems for complete grid independence can be costly as the PV array and batteries need to be quite large and could need to be replaced every 5 years or so.) However, you still have to pay an electricity service charge to the City as the City is still providing your home with all the potential to be connected to the grid. This service charge helps to meet the infrastructure and maintenance costs.

If you are planning to connect your solar PV system to the municipal grid, you will need to apply for approval. Connecting without approval is illegal and dangerous. The approval process for a small-scale embedded generation (SSEG) installation in the City of Cape Town’s electricity area varies depending on the size of the system and consumer category.

The application forms that are required from the City of Cape Town Electricity Generation & Distribution Department include the following:

• Application form for the connection of Embedded Generation (GEN/EMB form)

• Supplemental contract for installation of Small Scale Embedded Generation (SSEG).

These forms are available the City’s Electricity Generation & Distribution Department website: www.capetown.gov.za/ElecServiceForms

Existing legislation requires that anyone generating electricity “not for own use” must obtain a generating license from the National Energy Regulator of South Africa (NERSA). The City of Cape Town currently does not require embedded generation systems smaller than 100 MVA to obtain such a license provided that, over any consecutive 12-month period, they do not feed more electricity onto the City’s grid than they purchase from the City. 

The City is currently investigating the feasibility of relaxing the net consumer requirement and it may change. Therefore it is important to ensure that you have the latest versions of the application forms and other relevant documents before proceeding with an SSEG application. These are available on the City’s website: www.capetown.gov.za/ElecServiceForms  or www.capetown.gov.za/solarPV.

All embedded generation systems installed to connect to the City of Cape Town’s electricity grid must be signed off on commissioning by an ECSA-registered professional engineer or technologist who complies with the City’s requirements. There may be changes to this requirement once the SANS 10142-Parts 3 (The Wiring of Premises – Embedded Generators) and 4 (The Wiring of Premises – Direct Current and Photovoltaic) standards are published.

It is recommended you use a reputable installer who is accredited with a relevant industry association and has experience with the City’s authorisation process.

Until an SABS mark is issued for inverters, the City will require proof in the form of test certificates, of type tests having been successfully carried out by a third-party test company certifying compliance of the inverters with the requirements of the City and NRS097-2-2 (see step 6 in the main document). A full list of City-approved inverters is available at: www.capetown.gov.za/ElecServiceForms

The power generated by a PV system is determined by the number and type of PV modules used. The size of system needed is determined by evaluating the amount of electricity needed to run the appliances and equipment in a home or building, taking into account the amount of roof or ground area available. Typical home systems generate between 2 kWp and 10 kWp, which is usually enough to provide 40% to 100% of a household’s electricity needs.

A PV system will not generate electricity at night. Sunlight must be present for solar PV to produce power. At night, electricity is typically drawn from the utility’s grid. If a PV system has batteries, electricity can be drawn from those at night.

Yes, though PV modules will produce less electricity. Under a light overcast sky, panels will typically produce about half as much as under full sun. During the design of a PV system for a household a solar analysis conducted on the installation site takes into consideration the average amount of the sun’s radiation reaching your system and accounts for cloudy, rainy and foggy days. This information is based on weather data collected over a 15-year period by Solar GIS and by SASRAD (for example): An hourly-time step solar radiation database site throughout our region.

A steady rain is great for cleaning your solar modules. However, it will decrease your electricity production while it is raining and overcast.

The solar modules are made of tempered glass with a silicon filler and PVC backer. This will absorb the impact of large hail. The module design is tested to withstand hail.

Yes, but for businesses only. National Treasury has revisited Section 12B of the Income Tax Act No. 58 of 1962, as amended, providing for an ‘accelerated depreciation’ capital allowance for movable assets used in the production of renewable energy- including for solar PV. As from January 2016 Section 12B was amended from a three year (50% – 30% – 20%) accelerated depreciation allowance on renewable energy to an even quicker depreciation allowance of one year (100%).

This accelerated depreciation allowance came about from a proposal in the 2015 draft Taxation Laws Amendment Bill that the definition of solar energy be amended to distinguish between photovoltaic solar energy of more than 1 MW, photovoltaic solar energy of less than 1 MW and concentrated solar energy. It now provides for an accelerated capital allowance of 100% in the first year, in respect of photovoltaic solar energy of less than 1 MW.

The payback period will depend on the nature and cost of the PV system, your consumption patterns, how you are financing it (e.g. from savings, your existing bond/ homeloan facility or a higher interest-bearing bank loan) and future electricity tariff increases. At the moment, a grid-tied PV system with no battery has a typical payback period of about 6-9 years, but this is variable depending on the kind of factors mentioned above.

Most PV modules come with a 25 year power output guarantee from their manufacturer (and are typically expected to last at least twice that long). This means that after 25 years, the solar panels are guaranteed to still produce at least 80% of their original power output. Battery life span varies between 5-10 years, and depends on the type and quality of the batteries, as well as how often they are charged and discharged (‘cycled’).

When you sell your house the solar PV system usually remains on the house.

It is important to pass on all the system information, guarantees, etc. to the new owners who must sign a new Supplemental Contract for Embedded Generation with the City or decommission and remove the system.

PV systems can be covered by your homeowners’ insurance as a dwelling extension. Be sure to check with your insurance company to make sure that your system is covered and that you have enough coverage to repair or replace the system if needed. You will need to specify the system on your policy.

Solar PV power works for most homes. Systems are engineered to work with most roofing materials, in most locations where direct sunlight is available, in almost every region of South Africa. A PV system needs a sunny roof space. Any shading from trees or other obstructions can be a problem, so needs to be carefully noted and managed. A north- facing roof area is best, but PV panels can be mounted on north-west- or north-east- facing roofs and still produce adequate power as long as they do not deviate more than 45 degrees either direction from true north. It’s best to ask a PV professional to come and check out your home and give the best possible advice.

Your PV installer professional will also be able to give you advice on whether or not your roof structure can withstand the weight of the system, although this is not usually a problem.

A solar PV system does not need to provide all the electricity you need to be of great value. A small system that simply reduces the amount of grid electricity used can still significantly lower your electricity costs. A system with a battery backup can deliver uninterrupted power to critical loads during load-shedding or other outages, in some cases for days. While many people plan to get a system that supplies 100 percent of their energy needs, installing a smaller system may be more affordable and still make a big difference.

Solar PV systems typically operate virtually maintenance-free for years without problems. The batteries in a residential system may need replacement every 5 to 10 years, depending on the batteries and how they are used during their lifetime. It is recommended that the installer check the system annually, just to make sure everything is performing as it should. If it is convenient and your installer suggests it, you can clean off the PV modules with water one or two times a year to remove dust or dirt, and salt build- up in coastal areas. PV modules have a typical life span of 20-25 years.

A good rule of thumb is to allow 9.5 square meters for every kilowatt (kW) of electricity production needed. A typical residential solar PV system of 3 kW will require approximately 30 square meters. Note that these are figures for north-facing roofs without shading or obstruction.

The following factors will affect the roof space required, and need to be accounted for in the design of any system:

Shade-free roof area:
Shadows affect PV in two ways: lower efficiency due to blocking of the sun’s rays and shorter life span of the panels because commonly shaded modules burn out faster. The burnout is due to the shaded portion of the panel turning into a resistor instead of its normal function as a conductor when in the sun. This heats it up and over time burns it out, requiring replacement of the entire panel (the cost of which will not be covered by warranty).

Panel efficiency:
Less efficient PV panels need more panels – and therefore more rooftop space – to generate the same amount of electricity as more efficient panels.

Weight of the system:
PV panels are fairly heavy (about 20-40 kg/m2). They typically do not pose a problem for concrete roofs, but roofs made from other materials may require a professional design engineer to check out risks from point loads and wind loads, and make recommendations for any modifications to the roof.

Angle of roof:
The farther off of true north and the ideal angle to the sun a PV panel is, the less efficiently it operates. This means more PV panels needed – and therefore more rooftop space – to generate the same amount of electricity as the same panels at the ideal angle

Some homeowners’ associations have rules regarding the installation of anything on your roof or grounds. If you belong to a homeowners’ association, consult them for details before you install a PV system.

Rooftop solar PV panel mountings need to withstand wind pressure that builds up under the panels during heavy winds. This is an important consideration if you are located in a part of Cape Town prone to high winds. Discuss the kind of mounting required for your location and type of roof with the installer.

Mounting systems on the market today are made entirely of anodised aluminium and stainless steel to ensure long life without rusting. A racking system on a typical residential roof attaches through the shingles to the rafters using stainless steel screws. The attachment areas are then sealed with a high-quality polymer sealant for water tightness. Other types of roofs have different mounting systems, which are best discussed with the installer.

Not typically. However, PV panels are designed to last more than 25 years and if the roof is going to need replacement within the next 8-10 years, it would probably be replaced first. If the existing roof has plenty of life still in it, the installed solar panels will reduce wear on the roof by blocking ultraviolet rays, keeping most rain and dust off the roof, and preventing anything from hitting the roof.

There are options for ground-mounted PV installations. Speak to the installer for details on this.

The greatest efficiency comes from modules facing due north and at the ideal tilt angle. North is best, but modules installed facing northeast or northwest still generate a very high percentage of possible power. The rule is not to deviate more than 45 degrees from true north. Ask the installer to perform a comprehensive site evaluation to determine the efficiency of the system, taking into account shading from trees or other sections of the roof.

What you need to know:
Typically payback periods for standard flat plat collector close-coupled Solar Water Heaters is between 3 and 6 years depending on water consumption and how you’re financing the system.

Additional information:
The answer varies for every household, depending on the model purchased, how much hot water is used, and other factors. The general guideline is that a solar water heater can typically save up to about 60% of your hot water bill as your geyser accounts for the majority of your household consumption.

Generally speaking, if you are using 450 kWh or more per month for electricity – then you are likely to make significant savings from a solar water heater.* Households spending less can also save significantly, but behaviour will be a bigger factor to consider.

Savings will vary from month to month based on household usage patterns (e.g. visitors, holidays, travel, etc.) and seasonal weather.

As tariffs could increase steeply in years to come, the savings will only increase.

Be careful to avoid the ‘rebound effect’: this is when households unconsciously use more electricity on other things or even take longer showers because they know their water is now heated by sun and that they are saving so much electricity, and so do not experience the anticipated savings.

*Every household is different. All figures given are only indicative and can change over time.

The best ways to maximise your electricity savings through your solar water heater are:

• Install the correct size system for your home and family’s needs to start with.
• Use hot water in your home efficiently. This means good habits of short showers (rather than big baths) and help from technology like installing efficient, water- saving shower heads and tap aerators on all showers and taps in the household.
• Ensure you have a timer installed to boost the heat of the water (if required) just prior to using it. See “What times should the electrical backup be set for, and why?” for more information.
• If you want to take saving really seriously, you can opt to turn your system’s back- up element off and live with cooler water when the sun’s energy cannot be used to re-heat water in your geyser e.g. very cloudy days or for morning showers when all the hot water was used up the night before.
• Regularly clean your solar collector panel, so that the maximum amount of sun’s energy can always be absorbed.
• Service your solar water heater regularly according to the manufacturer’s recommendation.

The price of a solar water heater varies based on size, quality, complexity of installation, configuration of solar water heater, whether a service contract is included, warranties, certifications (plumbing or electrical compliance certificates), and other factors.

The cost for a typical direct, thermosiphon, close-coupled system with a flat plate collector including VAT and installation is between R15000 – R35000.

For more information refer to question “What are the different system options and configurations for solar water heaters?” below

Currently, there is no subsidy for solar water heaters or heat pumps available. The previous solar water heater rebate through Eskom was terminated at the end of April 2015.

The sooner you get a solar water heater or hump pump, the sooner you start, the greater your savings will be. A Service Provider can provide information about the instalment finance facilities to you. Alternatively, you can consider renting the product – a small number of Accredited Service Provider’s offer this option.

Yes. It’s not great that your geyser has burst, but the good news is that this is the perfect opportunity for you to upgrade to a solar water heater or a heat pump.

If your geyser has burst, check out our burst geyser upgrade guide for easy step-by-step guidance. Even if your geyser hasn’t burst it is always worth being prepared in case it happens – see this guide to plan ahead to get a solar water heater when your geyser next bursts.

Quality can be determined by many factors, including quality of components used and the installation itself. You should ask to see the SABS (South African Bureau of Standards) mark (or similar international certification) on all components used.

A proper quality installation is also essential. Installations must comply with SANS 10106 and SANS 10142-1, the national standards for installations. Certificates of Compliance (CoCs) for the plumbing work and a separate one for the electrical work will provide additional documentation of quality installation.

Your accredited provider will inform you of the best options for a good installation on your property, but it’s always good to be informed. Here are several points that should be kept in mind to help ensure a good installation:

• Solar collectors must be orientated and inclined correctly during installation. In South Africa, collectors should face true north or slightly to the west to take advantage of higher irradiance in the afternoon. A deviation of 45° east or west is acceptable, but deviation greater than this will require larger collectors to compensate for solar losses.
• A rule of thumb for pitching the collectors is “latitude +10°”. This gives the best uniform solar collection throughout the year. Vacuum-tube collectors are less orientation-sensitive than flat-plate collectors. Additional framework may be required to achieve the desired angle for the collector.
• Solar collectors should be placed in an area of uninterrupted sunlight. If an area is in shade between 9am and 3pm, another position should be found. A simple rule is to position your collector a distance from the obstacle that is twice the height of the obstacle. Partial shading by obstructions such as chimneys and T

Generally speaking a 5 year warranty on all major components is worth looking for. There may be exceptions for some smaller components, so the entire system may not have such a warranty, or you may need to pay extra for it. Some components are designed to be replaced, such as sacrificial anodes inside some hot water tanks (which help prevent rusting in some systems), so are often excluded from warranties. The tank and the collector normally carry a longer warranty of 10 years from the manufacturer.

A heat pump takes heat out of the surrounding air, which the sun warms up daily – like an air conditioner working in reverse. It uses some electricity to power a small ‘pump’ that moves the heat, compressing it for greater effect, from the surrounding air into the geyser.

A heat pump, like an air conditioning unit, is a vapour compression cycle, and works on the same principles as a refrigeration cycle. Where an air conditioning unit is used to cool air with heat as a by-product, a water heating heat pump can use the heat generated to further improve its heating efficiency.

    Diagram: How a heat pump works

A heat pump works during the day and at night, and does not need to switch to an electric element on cloudy days, like a solar water heater does. A heat pump uses some electricity to power a small ‘pump’ that moves the heat from the surrounding air into the geyser.

Heat pumps require regular annual maintenance (as do some solar water heaters).

There is currently no SABS standard for heat pumps, so judging the quality of any brand or model requires a bit more effort by the consumer. It is important to consider the warranty offered on any heat pump sold, as well as any international certifications of quality, among other factors.

Using a heat pump can typically save about 25% of your monthly electricity usage, similar to solar water heaters.

Comparative advantages of a heat pump over a solar water heater:

• A heat pump works during the day and at night, and does not need to switch to an electric element on cloudy days, like a solar water heater does.
• Heat pumps can be the better option for houses with lots of surrounding trees that shade the roof, for flats and sectional title units, for old houses with roofs that might not support the weight of a tank, and for new houses where there’s no room for the tank in an attic space and the aesthetics of a roof-top tank is an issue.
• Heat pumps also perform well in coastal areas where fog and haze can limit the performance of solar water heaters.
• They are easy to install and take up less area than solar panels would to provide the same amount of hot water.
• A heat pump hot water system can be integrated with the HVAC system for further savings.
• It is an important technology for the commercial sector where large quantities of water are being heated and stored – such as in hotels and hospitals – and the energy savings offset the higher capital costs of the pumps.

Disadvantages or barriers:

• Heat pumps require regular annual maintenance (as do some solar water heaters).
• When the heat pump is operating it can be noisy depending on the model, its position and how it is mounted.
• Due to the fact that heat pumps are still dependent on a supply of electricity, they are not a feasible option for households that are not electrified and won’t function if the electricity fails.
• There is currently no SABS standard for heat pumps, so judging the quality of any brand or model requires a bit more effort by the consumer. It is important to consider the warranty offered on any heat pump sold, as well as any international certifications of quality, among other factors.

This information comes from Sustainable Energy Africa “Sustainable energy solutions for South African local government: A Practical Guide” (August 2017). You can read it online here.

Solar water heaters use energy from the sun to heat water. A typical flat plate system is based on two facts of physics: dark coloured objects absorb heat, and hot water rises. The heat from sunlight is absorbed and transferred to the water, which is stored in a geyser or tank. There are two main types of solar water heaters, and they may be configured differently.

A typical system has three major components: a solar collector, a heat transfer medium and a storage container.

• Collector types and how to choose 
• Direct vs Indirect systems
• Installation methods: Close coupled or split systems
• High pressure vs low pressure solar water heaters

Collector types

There are two main types of collectors: flat-plate collectors and evacuated or vacuum tube collectors

A flat-plate collector has a transparent cover made of specially toughened glass, a coated metal absorber plate (coating is usually matt black paint), and a well- insulated weatherproof casing. Flat collectors are robust, economical, and versatile.

Vacuum-tube collectors consist of a series of glass tubes connected together. The absorber strip in an evacuated tube collector is placed inside the toughened glass tube, which can withstand considerable pressure. The heat transfer fluid flows through the absorber directly in a U-tube or sometimes in a tube-in-tube system. Several tubes are connected to one another or to a manifold that makes up the solar collector. A heat pipe collector contains a special fluid that vaporises at low temperature. The hot vapour rises in the heat pipes and warms the heat transfer medium in the main pipe before condensing and recirculating. The pipes must be at a certain angle to facilitate the process; too flat or too steep an angle and the system will not work.

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Vacuum-tube collectors advantages / cons:

How to choose which type of collector you need:

Your roof will help determine how you should heat water. If you have a roof that faces north – or at least between northeast and northwest – and gets full sun, flat panels are the most trouble-free option and will provide most of your hot water needs. If your roof gets limited sun, evacuated tubes may be necessary to provide enough hot water. And if your roof gets very little or no sun, you will be best advised to purchase a heat pump instead.

Direct vs Indirect systems

There are two main types of systems, corresponding with the two types of collectors:

In Cape Town, there is no risk from freezing and hard water is very uncommon, so direct systems are well-suited for local needs.

Installation methods: Close coupled or split systems

This refers to where the storage tank is situated in relation to your collector, and determines if you need an electric pump to circulate the water between the two or not.

Close-coupled system

This is the most common and least- expensive position for the tank. The storage tank is positioned just above the panels, lying horizontally.

The main advantage of close-coupled solar geysers is that they require no electricity or moving parts to circulate. This circulation is called the thermosiphon effect.

These solar geysers have fewer parts to possibly fail over time and need less maintenance. They even work when the electricity fails.

Split system

Here, the panels, or the collector, are on the roof, but the tank is inside the roof (typically in a vertical orientation).

These installations are more customised and more expensive, but can make moderate improvements in efficiency compared to a close-coupled system. A tank exposed to the outside air will lose more heat at night than a tank indoors, and a vertical tank will retain more heat than a horizontal tank

This positioning often uses a small pump to circulate the heat from the panels to a tank or tanks located close to bathrooms and the kitchen – meaning they require electricity to work

Split systems are commonly used when the aesthetics of having a visible or exposed tank are a concern.

High pressure vs low pressure solar water heaters

Low pressure solar water heaters provide gravity-fed hot water pressure only, and typically do not have a backup electrical heating element.

High pressure solar water heaters provide hot water at pressures commonly found in homes and businesses, and have backup electrical heating elements to provide hot water when solar radiation is too low or at night.

Installing the correct size of system is key. You should be able to store enough hot water to get your household through most 24-hour days worth of need, and also through a cloudy day. The general rule is a minimum of 50 litres of tank storage per person, plus another 50 for the house.

If you need more than 300 litres of hot water per day discuss with your installer the option of splitting the total into two tanks, with water flowing from one tank to the next, in series. That way, when you use water, it is replaced by heated water from the supply tank, not by cold water. And if you need to heat the water electrically before your morning shower, you only heat a smaller tank. A less expensive – and somewhat less efficient – variation of this idea uses an existing geyser, supplied with hot water from a solar tank. This is called a pre-feed system

Yes, you should have a timer for the electrical backup of your solar water heater.

A solar water heater should eliminate most – but not all – of your electricity use for water heating. However, an electrical back-up element in the tank is standard for most high- pressure systems. In the summer, electrical back-up may not be needed at all, and you may choose to switch off the electricity to the geyser at the DB board.

But with cloudy weather or a weak winter sun, extra heat will be needed to bring the warmed water up to a hot enough temperature. The key to saving energy is to avoid heating the water with electricity just before the sun gets to work. Therefore, every solar water heater should have a timer on the electrical backup.

The timer on electrical backup of your solar water heater should keep electricity to the heating element off during the peak daylight hours of sunshine, switching it on if needed at about 4pm for an hour.

This is if you use a lot of hot water during the day or if it is cloudy. If your family is in the habit of showering and bathing at night, you can save the most by keeping the electricity off until just before its needed again. If morning showers require extra hot water, experiment with a short 1-2 hour boost at 3 to 5am, shutting off by 6am for the rest of the morning.

A thermostat timer allows the extra control of setting different temperatures for different times of the day.

60 degrees Celsius is generally the best temperature, but many can get away with 55°C especially in summer months. Don’t go below 55°C because of the risk of bacteria growth.

More than 60°C is usually not a good option as your backup element on the solar water heater will be heating the water too much and using more electricity than you need (costing you more). Typically, a 10°C reduction results in saving 5% on your hot water electricity bill.

One hour is a good rule of thumb, but this will vary by the size of the tank, how cool the water was, the model and age of the heating element and other factors.

A remote thermostat control may be a good option for you, if you are testing whether 55°C or 60 °C works best for your household, or adjusting the temperature often, or have other reasons for changing the thermostat for your hot water, and you need to climb onto your roof or into your attic to do so.

Note that this function (i.e. thermostat or temperature control) is different from what a timer will do (i.e. turning the electricity to the unit off and on), and some remote thermostat controls also include a timer.

What a remote thermostat control can also do, depending on where it is placed and who sees it, is raise awareness in the household of hot water heating and energy conservation issues, leading to behaviours that result in using less hot water.

No, but you’ll save more if you bath or shower at night to take advantage of the water heated up during the day.

Maintenance for solar water heaters varies by type and installation. Generally speaking, the more complex installations with more moving parts require more maintenance to keep performance up.

Generally speaking it’s a good idea to have your Service Provider check out your solar water heater once a year or so.

Solar collectors must be clean to be effective. Generally, these can be cleaned as part of the annual maintenance. However, if you live in a very dusty area, an area subject to dust or sandstorms, or where coastal build-up of salt deposits from the ocean can be a problem, the glass panels of the collectors should be washed with clean water at least once every three months in winter and once a month during the remainder of the year.

Evacuated tube systems may require re-evacuation a few times during their expected life. Please consult your supplier for maintenance requirements.

Indirect systems need replacement of the transfer fluid every 4 to 5 years.

Your hot water storage tank has a ‘sacrificial anode’ in it, which helps prolong the life of the tank. This may need to be replaced every few years, but will vary by household.

High pressure solar water heaters (ie. with a pressurised tank), whether they are flat- plate collectors or evacuated tubes are not at risk of damage from low water pressure or short periods of no pressure (water outages). Please see this advisory by the City for Cape Town for more information.

SANS 10400-XA requires that at least 50 % (volume fraction) of the annual average hot water heating requirement shall be provided by means other than electrical resistance heating including but not limited to solar heating, heat pumps, heat recovery from other systems or processes and renewable combustible fuel."