More and more homeowners are installing solar photovoltaic (PV) systems to generate electricity from Cape Town’s abundant sunshine. Most of these homeowners are covering some of their electricity use and some are even selling excess electricity back into the grid. The investment case for installing a PV system is growing as the cost is reducing, and as electricity tariffs rise steeply. In addition, South Africa’s national electricity supply shortage will still be with us for years to come. The City of Cape Town encourages residents to use this renewable energy source where it makes sense for their home. To help make informed decisions and responsible choices please see the below FAQs, and note the new requirements for safe and legal PV installation.
Note that these FAQs are not repeated in the FAQ page of this website.
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 systems are very reliable and clean sources of electricity that work well for a wide range residential, industrial, commercial and agricultural uses.
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, which is different from the way electricity normally flows from household or commercial sockets and connections. (See definitions of DC and AC currents below).
Diagrams from www.sunlifeglobal.com.
Note that not all systems have a PV generation meter, and the City of Cape Town does not require one.
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:
No, not directly and not usually. Solar PV modules convert sunlight into electric current to operate appliances, motors, pumps and other devices. Solar water heaters and solar pool heaters use the energy of the sun to heat water directly. People often confuse PV systems with the kinds of solar water heaters that have their tanks in the roof and have similar looking solar thermal panels on the roof, and with solar thermal panels that heat water for swimming pools. Technically, a solar PV system can generate electricity to heat water in a geyser (amongst all the other things it can power) but solar water heaters are still much more cost effective than PV for heating water. So it doesn’t make sense to heat water with PV now, and it’s unlikely to for quite a few years to come.
PV panels or modules are the thinner ones, typically 2,5 to 5 cm thick with an array of 7,5 to 10 cm blue or black solar cells on the back of the cover glass. Solar water heating panels are generally much thicker, and also are typically connected to a water tank above it.
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. Other solar technologies, such as heat pumps, are designed to turn the sun's energy into heat instead of electricity.
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.
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), such as at a mountain cabin or an isolated farm cottage.
Without a battery backup, a grid-connected PV installation will not automatically provide electricity during load-shedding or other power outages. When the utility grid goes down, the PV inverter will automatically disconnect from the grid. If you do not have a battery backup, you will not get any electricity generated by your PV system. However, if you do have a battery backup, and are grid-tied, the changeover switch on your electricity board must be activated to shift the house wiring from the grid to the batteries. (Note that it is important to have a changeover switch installed, so request one because they are not ordinarily provided) If your PV system runs a section of your household independently from the grid, then this section will continue to function as per normal during a utility power outage.
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.
An inverter converts direct current (DC) into alternating current (AC) in a way that lets the PV system power appliances in the home and be connected to the utility grid.
A solar charge controller or regulator regulates voltage and current generated by the PV panels to keep batteries from overcharging.
Direct current is electrical energy that flows in one constant direction. DC is typically converted to alternating current (AC) for practical purposes, as most modern uses of electricity require AC.
Alternating current is electrical energy that changes direction at a fixed frequency (i.e. it ‘alternates’) as it flows. Most residential and commercial uses of electricity require alternating current.
A power utility is the electricity distribution service provider that 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 network within the City of Cape Town’s formal metropolitan boundaries.
A bi-directional meter is one that separately measures electricity flow in both directions, incoming and outgoing, or ‘importing’ and ‘exporting’.
Anti-islanding refers to the ability of a small-scale embedded generation (SSEG) installation – like a solar PV system feeding into the electricity grid - to instantly and automatically disconnect the generator from the local utility grid whenever the grid has a power outage. This is important as it prevents sending electricity to the utility grid from the SSEG during an outage. This is done primarily to protect utility workers who may be working on the utility grid and who may be unaware that the grid is still having electricity sent to it by the SSEG.
A small-scale embedded generation (SSEG) installation (like solar PV) that is connected to the utility’s electricity grid either directly or indirectly through a building’s internal wiring is said to be “grid-tied”. By being grid-tied the SSEG can provide electricity to the grid whenever generation exceeds consumption. They can also take electricity from the grid when their own generation is too low. In Cape Town, only SSEG’s connected to the City of Cape Town’s electricity grid (and not Eskom’s) currently have the option to become grid-tied. i.e. those who buy their electricity from the City of Cape Town, in their electricity distribution area, not Eskom’s.
Generating capacity refers to the maximum amount of electricity that a PV system can provide as AC. It is measured in kilowatts (kW).
Yes, if you wish to feed your excess energy from your PV system into the electricity grid. 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. A grid-tied system will require a new meter that reads electricity use in both directions, 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 Services Department will help you with the documentation and procedures. The guideline document explaining how to connect to the grid is available on their website at: www.capetown.gov.za/ElecServiceForms
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 in the day when the home needs more power than the solar PV can provide, and obviously 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 batteries for complete grid independence can be costly as batteries need to be quite large and could need to be replaced every 5 years or so.)
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 Services Department include the following:
These forms are available the City’s Electricity Services 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). Clarity is still required from NERSA whether feeding surplus generation back onto the utility grid and then drawing the same amount of electricity off the grid at a later stage for consumption is regarded as being “generation for own use”. In the absence of this clarity, the City of Cape Town currently does not require SSEG’s smaller than 1 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. As these temporary requirements are likely to change, 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
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.
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
If the PV system (Small Scale Embedded Energy Generation – SSEG) is not grid-tied in the electrical installation to the City’s electrical network, a registered person in terms of the Electrical Installation Regulations (2009) must install the SSEG and issue a certificate of compliance to the owner in terms of the South African National Standards for the wiring of premises (SANS 10142-1 – Low-voltage installations), that confirms that the SSEG is not grid-tied to the City of Cape Town’s electricity network and that it supplies an off-grid electrical installation. The City can request a copy of the Certificate of Compliance (CoC).
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 kW and 10 kW, 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 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: 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. 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 photo-voltaic solar energy of more than 1 megawatt, photo-voltaic solar energy of less than 1 megawatt and concentrated solar energy. It now provides for an accelerated capital allowance of 100% in the first year, in respect of photo-voltaic solar energy of less than 1 megawatt.
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 8 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 PV system usually remains on the house, although it could be moved to a new home. However, since a system is designed specifically for the original home, you would need to check if your system would be optimal for your new home.
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. Note that your roof may also require a structural assessment.
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 utility 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 hose off the PV modules two or three 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 20 square meters. However, 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:
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 should probably be replaced first. If the existing roof has plenty of life still in it, the installed solar panels actually 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.