Don’t be left in the dark – plug your home into a battery

“The issue with existing batteries is … that they suck.” That’s not the kind of quote you’d expect from Elon Musk, a guy who has founded three businesses that depend heavily on battery technology.

Musk’s newest product, the Powerwall, is essentially just a big battery – big enough to power your entire house for several hours. What makes it different is the technology it uses. Instead of the old fashioned lead acid batteries that you’d find in cars or other industrial applications, the Powerwall uses lithium ion cells.  

Lithium ion cells are much more energy dense than older battery technologies. In other words, they hold more electrical energy per gram of weight, which is why they are used in devices like cellphones and laptops where weight is a critical factor. That makes the Powerwall relatively compact for the amount of power it puts out. It weighs a hefty 100kg, but that’s roughly five times less than the equivalent lead acid batteries.   

The standard model has a capacity of 7kW/h. To put that into perspective an average South African household consumes around 15kW/h per day, so one Powerwall would see you through a morning or an evening, but you’d need two (they are designed to be modular) to be totally off the grid for an entire day.   

Tesla’s expertise in lithium ion cells comes from a decade of building electric cars. Its design team also knows how to make products that are as beautiful as they are functional. As such the device is sleeker and more attractive than any other battery on the market, and is designed to be mounted unobtrusively on a wall. This is the Apple Macbook of home batteries.   


And yet Musk is right about batteries – they do still suck. Whereas other electronics double in power and halve in price every 18 months, advances in batteries crawl along and they remain stubbornly expensive. Unlike silicon chips, the physical properties of batteries are simply more difficult to manipulate and optimise. 

Part of the reason batteries remain relatively expensive is that their supply chain is so widely dispersed. Raw materials and components often travel tens of thousands of kilometres, hopping between continents as they move from refiner to component manufacturer to device manufacturer and finally the end user.  Musk and his partners have a risky but brilliant solution to this problem: build the world’s biggest battery factory out in the Nevada desert. In this “Gigafactory” the entire supply chain will be brought under one roof. 

Musk is essentially betting that if he can’t make batteries much better, he can at least make them much cheaper and in far greater quantities. That bet seems to have already paid off – the factory has received so many pre-completion orders that Tesla is already planning to build a second one.

Tesla’s primary market for the Powerwall is households with solar panels, or those planning to install them. This gives the device a powerful synergy with one of Musk’s other businesses – Solar City – that specialises in leasing and installing solar panels on homes. 

But Tesla has probably underestimated the demand for batteries in countries like our own, where electricity supply tends to be irregular. With a starting price of $3 000 the Powerwall is not cheap, but many South Africans would pay far more than that to be insulated from Eskom’s hated load-shedding. And while the Powerwall will only be within the reach of relatively affluent South Africans, this kind of technology might relieve some of the pressure on our national electrical grid.  

Electricity cannot be stored at a large scale – at least not at costs that make such storage economical. When you turn on your kettle a turbine in a power station somewhere spins a tiny bit faster to provide that power. If the peak demand for electricity exceeds supply, the grid can collapse, which is why load shedding is necessary. 

What technologies like Powerwall do is shift demand management from the centre (Eskom) to the edges (households). If even 1% of households could take themselves off the grid and rely on battery power at peak periods, it would make a marked difference.   Combined with solar panels, the Powerwall has the potential to make your home largely energy independent. At the moment, in South Africa, solar panels are even more unaffordable than batteries and so they’re not being installed here anywhere near the rate they are in the United States. 

But if Eskom continues its mismanagement of our electricity grid then the demand for these kinds of technologies, however expensive, will continue to grow. The fact that it’s also better for the planet is an unexpectedly positive side effect of governmental ineptitude. 

It’s wryly amusing that Musk, who was born and bred in Pretoria, may just have accidentally invented a solution to load-shedding while trying to save the planet, and yet most South Africans still haven’t even heard of him. Perhaps when he lands on Mars with his other company, SpaceX, we’ll finally give him a round of applause.

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