In a recent article, Geoff Russell took aim at Greens leader Richard Di Natale for living a ‘self-sustaining’ lifestyle in the midst of a sprawling metropolis. In this article, Russell expands on why battery powered houses are a bad idea.

You can bet that a newsreader who pronounces film as ‘fill-em’ will receive a flood of complaints. Similarly, spelling mistakes in the written word will be pounced upon by the eagle-eyed readers with howls of protest and claims of declining standards and the impending end of civilisation.

But when people screw up with numbers, there’s a stunned silence. Our innovation hungry Prime Minister recently announced $48m to combat falling maths science standards, but it isn’t just children that need help with numbers.

Take, for example, the Climate Council’s Tim Flannery and SBS journalist Emma Hannigan in a recent news report about household battery technologies. Flannery responded to Hannigan’s statement that sales of battery systems were predicted to be 50,000 per year for the next decade by saying “… when you get to that point, you won’t need coal fired power systems any more”.

Get any 10-year-old (with a phone) to do the maths. 50,000 x 10 is half a million batteries. And how many households do we have?

Maths won’t help you here, you need data. Google it… number of households in Australia. It’s about 9 million.

So will half a million batteries make a dent in our electricity emissions? A tad useless would be an appropriate technical estimate, but since household electricity is only about a quarter of electricity, it’s really a quarter of a tad useless.

Put simply, half a million batteries, at around $7,150 dollars each (current price) is an incredibly stupid way to spend $35 billion dollars [Correction: $3.5 billion. Thanks Vincent!]. For comparison, the United Arab Emirates bought 4 x 1.4 gigawatt South Korean nuclear plants for $20 billion (US) and they’ll all be running by 2020.

That would generate enough electricity to charge half a million 7kw Tesla batteries 126,000 times in a decade; if they could handle it. They are only rated to handle 5,000 charge discharge cycles.

But cost isn’t the biggest reason for not using big batteries in houses. Let’s consider the situation in Germany, mainly because the data comes easily to hand and because they’ve just wasted 15 years mucking around with renewables at great cost, but with trivial impact.

They expect to take 50 years to do what France did in 15 with nuclear power. Consider the following chart of German electricity use in January 2015.

Can you see the days with very little wind and sun? There’s one run of five in a row starting on the 19th of January. In the absence of their fossil fuel and nuclear plants, how much battery storage would the Germans need to cover this kind of run?

They’ve just signed the COP21 agreement that should stop them expanding their logging of forests for electricity; in fact I’d argue that Article 5 requires them to reduce it.

To make the maths trivial, lets assume they only need to supply 50 gigawatts of power for five days. That’s 5 x 24 = 120 hours. Do the sums and you’ll see that the batteries will need to supply 6,000 gigawatt-hours of energy (120 x 50). A gigawatt is a ‘1’ with 9 zeros. So, how many fully charged Tesla 7 kilowatt-hour Powerwalls would you need to supply this? All those zeros make what is a trivial calculation look complex: 6,000,000,000,000 divided by 7,000 is 857,142,857.

That’s 857 million batteries at a current cost of … $6.1 trillion dollars.

In the real world, many industries need their electricity in a particular form, but the numbers at least give us a feel for the scale of the problem.

But, as I said, cost isn’t the biggest reason people shouldn’t do this.

Consider the much-vaunted Tesla gigafactory? When it’s finished in 2020, it will produce batteries for half a million vehicles a year. That’s impressive and useful, but how many such giga factories will it take to supply batteries for those five days of German power?

Each year the giga factory can produce 35 gigawatt hours of battery storage. So how many years of production will it take to supply 6,000 gigawatt hours worth of batteries… 6,000,000,000,000/35,000,000,000… roughly 171 years; assuming Germany is the only customer.

You can do such calculations without all those zeros by using the Exp button on your phone calculator App.

But of course, real engineers wouldn’t use Tesla Powerwalls for such a purpose, they’d go for something much cheaper like pumped hydro. This is where you pump water from a low place to a high place when you have cheap electricity and then let it fall back down through a turbine to generate electricity at some later time.

It’s great when the geography is suitable and you don’t mind trashing some high mountain valley.

But surely batteries will get cheaper? Agreed. The Climate Council has just published a modest battery report. They make a general claim that the cost of battery storage should fall to $200 per kilowatt hour by 2020.

If that comes to pass, the Germans could provide for a run of 5 cold still days using an as yet undeveloped technology at a projected cost of just $1.2 trillion. That makes me feel much better!

So we probably can’t afford them, and it will be incredibly tough to build enough of them, but there’s still another far more important reason that using big batteries in houses, or for general grid backup, is dumb enough that it should be made illegal where there is no actual need.

Has the penny dropped yet? Here’s a hint. The world sells 70 million cars a year and the Tesla giga factor will make half a million car-sized batteries a year when it’s finished in 2020.

It should be obvious now… we will desperately need good, big batteries for electric vehicles.

Batteries and hydrogen fuel look to be our only choices for vehicles. So we shouldn’t be wasting valuable battery production resources to make batteries for houses because some puddle shallow thinkers reckon it’s cool to live off-grid.

We know how to cleanly and efficiently power houses; you build nuclear power plants and hook them into a grid. In developing countries, there is a pressing need for grids and that will be a huge challenge. Wasting valuable battery production capacity on powering houses will make everything that much harder.

The whole batteries-in-houses idiocy is part of what is inevitable when rich countries transfer spending decisions from Governments to individuals via low taxation rates and small government; or more accurately, incompetent Government; Governments who no longer have the skills and vision to pursue major projects in the national interest, let alone the international interest.

Traditionally, when Governments spent money, there was at least a fighting chance that a competent bureacracy would act rationally and in the public interest.

But when it’s up to individuals, particularly rich, self-centered individuals who can’t think quantitatively, then they will buy Tesla batteries and Tesla will happily supply them.

If Tesla boss Elon Musk had even half the environmental concern he professes, then he wouldn’t make the bloody things.