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Comment by patrickhogan1 | Hacker News Reader

Bingo! Solar energy moves us toward a future where a household's energy needs become nearly cost-free.

Energy Need: The average home uses 30 kWh/day, requiring 6 kW/hour over 5 peak sunlight hours.

Multijunction Panels: Lab efficiencies are already at 47% (2023), and with multiple years of progress, 60% efficiency is probable.

Efficiency Impact: At 60% efficiency, panels generate 600 W/m², requiring 10 m² (e.g., 2 m × 5 m) to meet energy needs.

This size can fit on most home roofs, be mounted on a pole with stacked layers, or even be hung through an apartment window.

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Everyone always forgets that they only perform at less than half of their rated capacity and require significant battery installations. Rooftop solar plus storage is actually more expensive than nuclear on a comparable system LCOE due to their lack of efficiency of scale. Rooftop solar plus storage is about the most expensive form of electricity on earth, maybe excluding gas peaker plants.

Everyone also forgets the speed of price decline for solar and battery your statement is completely false propaganda made up by power companies. Today rooftop solar and battery is cost competitive to nuclear already in many countries like India

Do you have some citations?

You’re right that rooftop solar and storage have costs and efficiency limits, but those are improving quickly.

Rooftop solar harnesses energy from the sun, which is powered by nuclear fusion—arguably the most effective nuclear reactor in our solar system.

It varies by a lot of factors but it’s way less than half. Photovoltaic panels have around 10% capacity utilization vs 50-70% for a gas or nuke plant.

The thing everyone forgets is that all good energy technology is seized by governments for military purposes and to preserve the status quo. God knows how far it progressed.

What a joke

While I agree with your general assessment, I think your conclusion is a bit off. You’re assuming 1kw/m^2, which is only true with the sun directly overhead. A real-world solar setup gets hit with several factors of cosine (related to roof pitch, time of day, day of year, and latitude) that conspire to reduce the total output.

For example, my 50 sq m set up, at -29 deg latitude, generated your estimated 30 kwh/day output. I have panels with ~20% efficiency, suggesting that at 60% efficiency, the average household would only get to around half their energy needs with 10 sq m.

Yes, solar has the potential to drastically reduce energy costs, but even with free energy storage, individual households aren’t likely to achieve self sustainability.

Average US home.

In Europe it is around 6-7 kWh/day. This might increase with electrification of heating and transport, but probably nothing like as much as the energy consumption they are replacing (due to greater efficiency of the devices consuming the energy and other factors like the quality of home insulation.)

In the rest of the world the average home uses significantly less.

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