CO2 repayment of a typical home system

A thought occurred to me this morning after someone asked (for the umpteenth time), in a discussion about EVs: Oh, but what about the carbon cost of making the battery? lolol :joy: etc etc as they do on social media. As if it is that simple to dismiss something.

So I thought, hang on… you can probably calculate this!

It has been said that I probably occupy my own little corner of “the spectrum”. I digress.

Production of a LiFePO4 battery is said to have a footprint of around 73kg/kWh.

Eskom’s footprint, according to this study done by Pepkor, is 1.06kg/kWh.

Therefore, assuming the energy I used to recharge that battery was 100% carbon neutral, does that mean the battery manufacturing cost can be repaid in about 70 days, or just over two months? Or am I being way too simplistic here?

I know the energy is of course not carbon neutral, it takes energy to make a solar panel. I cannot find a number of kg/kWp, which is what I would have preferred, but what I got says around 41g/kWh over the first “several years”. Which is unsuitably vague, but does suggest that the additional cost of making the solar panels is not going to turn 3 months into 3 years.

What am I missing?

Total footprint includes more than just manufacture. EG There’s the CO2 cost of transporation.

I got interested in my water consumption a while back and did some reading about this. The point was made that whilst reducing your metered consumption is a good thing (as long as things don’t get unsanitary), that is hardly the total water consumption of your house.

How much milk do you drink? Because that is mostly water, but doesn’t show on your meter. Red meat? That usually requires some degree of pasture (especially if you want “organic” or “grain fed” or some such) and the food used for the beasts has taken water to grow, and so the steak you throw on the braai can account for a good bit of water. Beer? Don’t go there.

The sums are difficult, is what I’m saying, because it’s hard to know all the inputs into the process that delivers the battery to your home. But I think you must win in the long run, because the manufacturing costs and transport costs are not recurring. It may take longer than you think, but you will win. Though at some point you’re going to have to replace batteries, but maybe they’ll have green lithium by then.

Nope: Because if you “save” 20kwh using battery/PV in the day then you would pay if off in a quicker time PLUS if you are grid tie with no/few batteries and can feed back to supply others then… even better!

Oh, I can imagine that. But my question remains, when I account for all of that, does it double my estimate? Triple it? Even if it is 12 times as much (and therefore turns 3 months into three years), that’s still a hugely favourable number, is it not?

Yes I know direct use would be even better. I’m using a worse case scenario here where someone is mostly grid neutral, ie he cycles that battery daily. Because the idea is to price the battery IN rather than OUT :slight_smile:

So the carbon cost of having energy at night is about on par with three months from Eskom. Plus whatever factors I did not think of, which I cannot imagine turns the exercise into a decade.

Yes it is. Using the figures you provided and averages I have from 4.5 years of use, I come up with about 70 days for my system to offset the C02 used to manufacture the battery. Let’s double that to include the panels and the inverter. Let’s then assume I’m wrong by an order of magnitude.

Yes… it’s the exercise you just did. I’m in the black now, and I can sleep tonight.

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One of the funniest things I’ve seen in a movie, was a scene where someone severely berates another character, ending up with the usual “Tell me sir, how do you sleep at night!?”, at which point his lady companion shows up and tells the other character about these excellent sleeping pills her doctor prescribed.

Edit: Found it. At 2:30 ish.

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