Duncan MacLeod recently wrote an article in the Sunday Times. It was all about Elon Musk, whose fame can be judged from the fact that his name is familiar.

According to MacLeod, Musk is now regularly compared to great inventors such as Thomas Edison and Henry Ford. Musk’s claim to fame is that he is the CEO of Tesla, which supplies electric cars, and is part of an organisation which launched a rocket that delivered supplies to the International Space Station.

But MacLeod’s article is all about a device called the Tesla Energy Power Wall. The company states on its website: “The Power Wall is a home battery that charges using electricity generated from solar panels, or when utility rates are low, and powers your home in the evening. It also fortifies your home against power outages by providing a backup electricity supply.

“Automated, compact and simple to install, the Power Wall offers independence from the utility grid and the security of an emergency backup.”

Depending on size, the Power Wall costs between $3 000 and $3 500. This excludes the cost of the solar panel or the dc-to-ac inverter which will be required if the device is to be connected to the domestic power supply.

Take a small version of the Power Wall, rated at a storage capacity of 7 kWh. To use it, you are going to have to supply a little over 7 kW for one hour to charge the battery up (the charge efficiency is about 90%). Thus, you will have to have about 9 kW of solar cells for charging the battery. At $2.50/W (installed), this is $22 500. The inverter will cost about $3 000. Thus, altogether, the cost of all components and the Power Wall battery will be $28 500 (R300 000).

Naturally, if one just buys the battery, the cost is only about R36 000 (as MacLeod points out). But it is not going to be much use as a battery on its own: what would you do with it if it does not produce 220 V? The battery is a lithium-ion battery and, consequently, lighter and more efficient than traditional lead acid batteries.

But is it a good thing? Candidly I think not. There is nothing new about the invention – it is a whole lot of lithium-ion batteries of the type used in cellphones. I worked out that eight cellphone batteries in parallel in a stack of 65 series groups will give you a battery with the same performance as the Power Wall. And it will cost you about R 6 000, about half the cost of the Power Wall.

Tesla does offer a temperature control unit, but this cannot be very complicated. Candidly, I see nothing in this idea.

However, there is one, dim (forgive the pun), hopeful flicker of light. It is the idea of using lithium-ion batteries for more than just powering cellphones. The battery on my cell phone (Nokia C1, not a smartphone) is rated at 3.7 V, 800 mA hours. This means it could power some light-emitting diodes – eight of them for quite a few hours. This, in turn, means that the real ‘Holy Grail’ of electricity is upon us: the provision of a lamp which charges up during the day with a small solar panel and which runs for six hours at night and provides the same light of the paraffin lamp. And costs no more than $5.

It would change the lives of hundreds of thousands of people. The Power Wall will change hardly any lives. But then is this what it is supposed to do? Or is it (as I suspect) just commercial hype.

Tesla’s net loss in the quarter to date is $103-million. This is a fortune. Perhaps they hope that the Power Wall will turn their fortunes around. The Power Wall battery, no matter its packaging, can easily be sold for a profit. It is convincing people that they need it. Internet advertising may do it. Word of mouth from happy, contented consumers would have to follow. I cannot see that happening.