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Off-grid vs grid-tie solar systems in sectional titles: what’s best?

09 Feb 2018

Electricity supply for individual flats, townhouses and houses is likely to continue to increase in price over the next few years due to the fact that Eskom has lost control of its finances.  

If the solar system is installed as part of the development, then the income from electricity sales would be used to offset the levy.

This is according to Mike Spencer, Master Practioner Real Estate, from Platinum Global, who says the current investigations and the downgrading of Eskom by international funders are an indication of the self-inflicted problems that they are suffering. 

A new Board at Eskom will assist the situation but it is going to take time to sort out their mess. 

Spencer says Body Corporates and HOAs are faced with how they are going to deal with the situation, both the high cost of electricity and whether the supply is going to be interrupted. 

He says solar and wind power may not be the total answer but can do a lot towards reducing the cost of electricity, and being a source of power when Eskom is off the grid. 

Wind power has the advantage of being available when wind is available and is more suitable to coastal areas where wind is more generally available.  Solar is suitable for the entire country, with South Africa having more than double the sun energy that a country like Germany has, and in many inland areas there are over 300 days of sun a year.  

Panels designed for desert conditions with very high temperatures like 125 degree C are essential, as the standard 85 degree C panels cannot take the temperature ranges in South Africa and will fail within 7 years or so (compared to over 30 years). 

Two types of installations can be considered 

1. Off-grid 

This is where the installation is designed to make the user independent of Eskom’s grid. It is successfully being used in isolated areas such as farms.  

Once installed, the user is then totally dependent on their solar plant for their electricity supply, and they have no access charges or electricity bills. It is certainly to be considered in isolated areas where the cost of running new power supply lines is too high.    

This type of installation is more costly as it requires an extensive power storage system that is able to retain enough power to supply electricity for three to five days in case of heavy, cloudy weather. It would also require a large generator to take over when bad weather lasts longer.  

Battery technology is improving by the year, and large and less expensive per watt batteries are continually being developed. For the time being, deep cycle lead acid batteries are currently the most appropriate batteries to use, but they need to be replaced on a fairly short life cycle of three to five years. This is somewhat improved if they can be installed in a cool and temperature environment. 

2. Grid-tie 

Here the system is used to supplement the supply from Eskom and to reduce overall cost of electricity supply.  

Grid-tie systems tend to be less expensive than off-grid systems. This type of system will reduce your electricity bill, but will not eliminate it completely.  

Solar panels provide a source of electricity when it’s sunny but not in heavy, cloudy weather or in the dark. During the day, it becomes a source of electricity and can be used for everything except heavy duty uses (ovens, geysers, aircons and the like).  

It is possible to install a system where lights, A-grade appliances such as flat screen TVs, plugs for small appliances such as radios, cell phone chargers, computers etc. can happily run off the system. Many of these heavy duty appliances can be taken off the electricity supply and replaced with gas or solar water heaters. 

Day-time use can be a big cost saver and the usage can be extended by installing a battery system for each individual unit or in larger complexes for groups of units. The batteries will usually be designed to cater for two to three hours of usage when the grid is down. 

The design of the schemes is vitally important. The way in which they are installed will allow for electricity to be supplied at a variety of tariffs. For example, a unit can be supplied, free of charge, if the owners pay the cost of installing the system, but the best charging method would be to meter electricity usage to each unit and to charge a reduced rate.  

If the system is installed as part of the development, then the income from electricity sales would be used to offset the levy. Even where income must finance the cost of installation, loans or leases are usually paid off over a period of three to five years, after which they supplement the cost of running the development. 

The installation cost per watt is roughly R20, but will vary on the difference in the type of installation required. The larger the installation, the more options will be available and the less expensive per watt costs will be.   

It is essential that your installer is fully experienced with each of the different types of installation.  

For more information on these systems, email Henry de Beer or call 083 457 7925.
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