Don’t let load shedding leave you in the dark

Is there a business case for a battery backup or is a generator the answer ? Contact us to discuss the pro’s and con’s and why one, the other or a combination may be the best option: Step one to solving you electricity interruption problem at no charge, no risk, no commitment. With load shedding becoming so regular that it is not newsworthy anymore, we have to use some alternative to the grid to ensure that our business or household can function for that few hours per day. There are two competing technologies, Generators and Battery backup systems, to do this. Generators are always people’s first thought, but battery backup systems gained a huge market acceptance with the inprovements in battery technology.

Inverter-Battery systems and Generators

An Inverter-Battery system is a silent electronic system that charges batteries, monitors the power supply and switches to battery backup within 20 milliseconds (1/20 th of the time it takes to blink) of the power going off. Modern lights, computers and the TV etc. will be unaffected by the switchover. When the power restores, the system waits a few seconds and then switches back to the grid power. You are therefore totally unaware of the system’s operation. When deciding between an Inverter-Battery system and a Generator you have to consider two things. The cost of generated electricity and the convenience of the system. Our studies for a number of companies to evaluate the cost of inverter-battery systems against generators show that they cost the same and mostly generator power is slightly more expensive. This was done by comparing the net present value (read cost) of electric power during load shedding over five years. Generators need more consideration than most people appreciate. Oversized generators will seize due to a piston sleeve effect called glassing and undersized generators simply stall. Running a generator for hours per day is an irritation, initially to your neighbours and, once the denial period expired, to yourself. Also, few generators were designed to run for long periods and still last. So, when you get near the end of the evening movie, while your kids want to sleep without the generator’s rattling, you may want to ask yourself why you did not take the more elegant and cheaper option.

What runs off the inverter?

Your inverter system capacity, has much less to do with how much you normally use, than with how much you are prepared to get by with, during power failures. With load shedding varying between 2 and 4½ hours, plus some losses, you have to work on the 5 hours capacity. Here are three options that we believe, you should consider:

a Priority 1 System

You have to limit your use to 240w average. You can use lights but they have to be LED, or at least Compact Fluorescent (CFL). Incandescent (filament) lights is a total no-no and 50w halogen down lights (12v or 230v) is an unspeakable sin. If you manage your lights down to using 4-6 at a time, that amounts to 35w for LEDs and 55w for CFLs. The TV and decoder uses 30w when off and 150w when on. A phone charger use as much as one LED light. So you can switch the TV and some highly efficient lights on.

a Priority 2 System

You have to limit your use to 480w average. Now you can increase lighting to 10-15 lights. You can have one energy efficient fridge / freezer on (but manage it well). Laptops can be used, but use the printer very little. Suitable for an average sized 3 bedroom house.

a Priority 3 System

You have to limit your use to 960w average. Lights and TV are no problem. Run multiple fridges and freezers but open them as little as possible. Run Laptops and printer. We have a Priority 3 system and the household functions close to normal during 4½ hours load shedding. We boil water on the gas stove, the geysers can heat when the power is back on, and we run 5 fridges / freezers (energy efficient one’s). Our biggest problem we forget the power is off. Priority 3 systems are also suitable for small offices, consulting rooms and shops. Bigger systems are really needed if you want to have a situation where you are totally unaware of the fact that the power is off or want to run a fair sized shop or business. Suitable for bigger houses that wants to be largely unaffected by load shedding.


There are many promises out there about what one can power for how long, so here is a bit of quantitative information about Priority 1, 2 and 3 systems. Priority 1 has a total of 2 x 100 Ah x 12v batteries. The inverter can provide 2400 Watt (10.5A) continuously and 1.2 kWh energy. Priority 2 has a total of 2 x 200 Ah x 12v batteries. The inverter can provide 2400 Watt (10.5A) continuously and 2.4 kWh energy. Priority 3 has a total of 4 x 200 Ah x 12v batteries. The inverter can provide 4000 Watt (17 A) continuously and 4.8 kWh energy. The batteries are Deep Cycle GEL batteries.


There are a few types of Deep Cycle batteries, all with different pricing and lifespan. Note the following: Design life (X years), is a meaningless statement. Batteries last for a number of cycles which normally get used long before the so called design life is reached. Heavy industrial batteries are the worst. They last 200 - 300 cycles and are not really intended for deep cycle operation. Maintenance Free batteries. These are VRLA (Valve Regulated Lead Acid) batteries, commonly called sealed lead acid batteries. They are most popularly sold in AGM and GEL formats. o AGM (Absorbed Glass Mat) is a deep cycle battery but expect 300 - 500 cycles. o GEL (Colloidal Silica added to the electrolyte to obtain a solid gel electrolyte. Expect 900 - 1200 cycles. o A newer option is a hybrid of AGM and Gel betteries which last about 2,000 cycles. o You are buying your last chemical battery now. The new development on the horison is graphene super capacitors. They will last infinetely longer than chemical batteries. If the Parthenon was equiped with super capcitors for backup power, and they had daily power failures in Athens, the super capacitors would last another 200 years from now. OPz Batteries. These come as OPzV and OPzS variants and are used in professional environments. They are not sealed and require topping up the electrolyte (like our parents used to do with their car batteries). They do however have a large internal storage so only need top-up every 3 months. They also have level indicators, so knowing when to top up is easy. They last 2500 cycles, hence why one would consider the hassle. So the choice now is really between GEL hybrid AGM/Gel or OPz or rubbish. Once my LiFePO 4 battery in my cellphone lasts longer than 2 years, I will consider Li-Ion technologies.


In short, the total project cost for a systems are: Priority 1 system is around R 32,000.00 which includes installation labour and materials. Priority 2 system is around R 45,000.00 which includes installation labour and materials. Priority 3 system around R 65,000.00 which includes installation labour and materials. All the above are rough estimates including VAT.

Change your Energy mix

In the days of cheap and ultra reliable electricity we became careless about energy use and, more important, we adopted electricity for all our energy use. With expensive and less reliable electricity we have to use a mix of solar heating, gas and electricity.

A proven recipe is:

Use Solar water heated geysers. Use Gas or Electricity as a backup. Use Gas for cooking and heating with electricity as backup. This leaves the rest to electricity. As with all new and growing industries, every opportunist enters the industry, selling things that he probably knows less about than he cares about you. It is important to quantify the continuous power, the cycle battery energy and the expected battery life in cycles.


Your system has to be installed by an electrician, and you do need a compliance certificate for the installation. You may need to move light and plug circuits in the Distribution Board (DB) and you will need an additional earth leakage and breakers. If space on your DB is limited, you will need a sub distribution board installed. Not all electricians are familiar with the requirements, but we will advice proper qualified electricians what to do.

Addition of PV Panels

PV panels are not required for power continuity. It is an advantage to have provision in the inverter for adding PV panels later. If you think power outages may become unmanaged and you may have to rely on Solar power to charge batteries during an outage for the next evening, then make provision for adding PV panels later. It must however be considered upfront, else you through away your original inverter.


Unfortunately systems are not readily upgrade-able to the next size. Old and new batteries do not work well together and switchgear has to be sized accurately to protect the system. Inverters has to be matched to the battery, else it may overload the battery and shorted it’s life.
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