[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.

[testing22321]

My 7.8kw system made 1000kwh in July, and 100kwh in December.

November and January were 200kwh each, and October and February were 400kwh each.

So it’s very low in the worst of winter, but it comes back very quickly.

[belorn]

Looking again at Swedish number, the average house need around 200kwh per month for the period of December to April, and about half that for the rest of the year (https://hemsol.se/wp-content/uploads/Elforbrukning-villa-02....). If your maximum is 1000kwh your battery need for the winter will be around 125-150 kwh, not counting capacity for harsher winters or degrading panels.

Using the power walls examples above, you then need around 10 units.

[wqaatwt]

> is arguing about the budget over a whole year

How and why does that change anything in any way?