[berdario]

A Tesla Powerwall3 (which apparently uses LFP) has a capacity of 13.5kWh

A household uses up at least around 2MWh per year, most of which during the winter, if you don't use air conditioning in the summer and don't have an electric car to charge.

That means you'd need around 150 (!) Powerwall 3 units. At a price of around 10k GBP each, you'd have to shell out more than 1 million pounds just for the batteries. Not to mention the space that they'd have to take, and the increased risk in having something failing.

In the USA, homes are even less efficient (and depending on locale, people run AC all year round, and drive tens of thousands of kilometers on cars which also need to be powered). 2 years ago MKBHD published a video about his experience with the Tesla roof:

https://youtu.be/UJeSWbR6W04

In it, he revealed that his yearly power consumption is 55MWh. His battery was able to tide him over the next cloudy day, and during the winter the solar panel wouldn't ever fully recharge again.

Expecting every household to be energy independent year-round via solar is patently absurd. Renewable energy tided over with massive batteries upstream? Maybe that could work, I haven't run the numbers... But you cannot hope to push that responsibility downstream to every household. Reliable baseline is still going to be necessary for the foreseeable future.

[hiatus]

Why would a household need enough batteries to store a year's worth of energy?

[berdario]

The grandparent comment is arguing about the budget over a whole year

https://news.ycombinator.com/item?id=43751178

> We use the grid like a battery, getting a one for one credit for everything we put in. So during summer/daytime we put in enough to then use up our credit in winter/nighttime.

> The power we put in even covers the monthly connection fee.

> I’m just about to hit 12 months with mine, 8 Mwh generated, never paid a bill.

And later the same commenter argues

> When that happens, I’ll get batteries.

[testing22321]

I am that commenter.

If I have to get batteries one day, I sure as heck won’t get a whole years worth of energy. In summer I’ll only need enough to get through the night ( very little ). In winter I’ll obviously need more, and I would have to carefully look at how much the house is using and how much solar I’m generating, but something like one or two power walls would do it. In five or ten years that’s going to be cheap.

[belorn]

That make perfectly sense if the climate is right. Energy discussions often get messy when people from different climates are talking about utilizing the same strategy, since different climate has different requirements.

Solar and batteries works great in climates with highly predictable weather and where demand only exceeds supply during very short burst. Europe, especially the northern part, are prime example where this is not the case and where supply shortages can occur for months. This is the reason why a single month of energy can cost more than the collective sum of all the other 11 months, since market prices follows supply and demand. This is where government subsidies will hide things with government funded fossil fueled power plants (under the euphemism of reserve energy and grid stability), and they can also just straight pay citizens energy bill when the price hit certain levels. When the government is responsible for energy storage, the cost is placed through taxes or tax-related fees. A common red flag here is when grid connection fees start to become bigger than actually consumption cost.

[testing22321]

I’m in a very snowy mountain town in Canada.

In 12 months the 7.8kw system has generated smack on 8Mwh.

While the very short days, snow and cloud cover reduce output a lot, it still makes power year round.

[belorn]

That is very surprising. Looking at the statistics collected from the Swedish grid (https://svensksolenergi.se/statistik/elproduktion-fran-solen... ,first graph), the winter months are close to zero in output. December 2024 were 35 GWH, while May 2024 were 765 GWH. In 2023, December were 14 GWH, while May were 579 GWH

It is not absolute zero, but it kind of close, and there is a large period that storage would need to fill. For Sweden it is also the inverse for the demand spike, with winter demanding more energy than during the summer.

[wqaatwt]

> is arguing about the budget over a whole year

How and why does that change anything in any way?