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> residential rooftop solar deployment is an expensive[2] fashion statement. Not really. Panel lifetimes are measured in decades and the break-even point is us

> residential rooftop solar deployment is an expensive[2] fashion statement. Not really. Panel lifetimes are measured in decades and the break-even point is usually around a decade, less if daytime utility power is expensive. They're not high volume money printers but they'll eventually pay for themselves (including their carbon usage during production). Solar works mathematically because the Sun is constantly bombarding the Earth with energy. Rooftop solar increases the efficiency of otherwise wasted acreage of rooftops of buildings. Not only can they offset energy use of the stuff inside the building but the rooftop shade is that much less cooling needed for the building.

vkou 4y ago
> less if daytime utility power is expensive. My point is that daytime utility power that comes from a solar farm will always be cheaper then rooftop solar. Because it takes a lot less labor to deploy solar at utility-scale, than to bolt it to your roof. The only reason rooftop solar can currently be cost-efficient[1] is if its competing with expensive sources of energy generation. If it has to compete with cheap sources (utility solar), it's not cost-efficient. [1] Or if you're receiving subsidies for the energy you sell back to the grid.
- freemint 4y ago
  > My point is that daytime utility power that comes from a solar farm will always be cheaper then rooftop solar. If you ignore the cost of maintaining the grid between A and B, yes and if you ignore the value of people having storage in their house being able to optimise their in house consumptions to match the solar production, yes (this would be possible with pricing signals but it is not done, also there are slight psychological differences for the user) and if you ignore communities having access to power in case the electricity grid is under attack due to foreign invasion, yes.
  - vkou 4y ago
    If your house is still on-grid, you still have to pay all of the grid costs. If your house is off-grid, and you have to invest tens of thousands of dollars into battery capacity, your economics will look worse then the grid's economics. Because if batteries were a cost-efficient way to deal with solar's intermittent generation, every utility in the world would be tripping over itself to order batteries by the TWH. They, uh, aren't. I also can't optimize my energy usage around the sun. I'm not home when the sun is shining. I don't have an AC. I don't run heat most of the year. I need electricity for lights (Because it's dark), and appliances (which I use when it's dark, because that's when I'm home). I would a lot of on-site storage to get me through the days when it gets dark before I'm home. This is not cost-efficient. It would be cost-efficient if my entire town could aggregate their generation and usage... At utility scale.
    - freemint 4y ago
      > If your house is still on-grid, you still have to pay all of the grid costs. Yes but building new solar causes new grid cost. > Because if batteries were a cost-efficient way to deal with solar's intermittent generation, every utility in the world would be tripping over itself to order batteries by the TWH. They are cost efficient in Germany. So i am not to familiar with other countries situation. > I also can't optimize my energy usage around the sun. With batteries you could do that more. Both have a role to play. Another reason for solar is that people rather invest $10000 in their house then $5000 in shares of a grid scale solar installation. So while it might not be capital efficient it unlocks more capital investment for the green transition. From an economic view roof top solar is a jobs program where well paying trade jobs are created all over the country.
      - vkou 4y ago
        Really? German utilities use batteries for day-night supply/demand smoothing? [1] How many GWH of capacity have they deployed? And isn't it the country where a KWH costs 33 cents? Given that solar produces electricity at ~2 cents per KWH, this seems pretty damning. [1] Are you sure you're not confusing this with minute-over-minute smoothing, which requires ~two orders of magnitude less battery capacity?

vkou 4y ago

> less if daytime utility power is expensive. My point is that daytime utility power that comes from a solar farm will always be cheaper then rooftop solar. Because it takes a lot less labor to deploy solar at utility-scale, than to bolt it to your roof. The only reason rooftop solar can currently be cost-efficient[1] is if its competing with expensive sources of energy generation. If it has to compete with cheap sources (utility solar), it's not cost-efficient. [1] Or if you're receiving subsidies for the energy you sell back to the grid.

freemint 4y ago
> My point is that daytime utility power that comes from a solar farm will always be cheaper then rooftop solar. If you ignore the cost of maintaining the grid between A and B, yes and if you ignore the value of people having storage in their house being able to optimise their in house consumptions to match the solar production, yes (this would be possible with pricing signals but it is not done, also there are slight psychological differences for the user) and if you ignore communities having access to power in case the electricity grid is under attack due to foreign invasion, yes.
- vkou 4y ago
  If your house is still on-grid, you still have to pay all of the grid costs. If your house is off-grid, and you have to invest tens of thousands of dollars into battery capacity, your economics will look worse then the grid's economics. Because if batteries were a cost-efficient way to deal with solar's intermittent generation, every utility in the world would be tripping over itself to order batteries by the TWH. They, uh, aren't. I also can't optimize my energy usage around the sun. I'm not home when the sun is shining. I don't have an AC. I don't run heat most of the year. I need electricity for lights (Because it's dark), and appliances (which I use when it's dark, because that's when I'm home). I would a lot of on-site storage to get me through the days when it gets dark before I'm home. This is not cost-efficient. It would be cost-efficient if my entire town could aggregate their generation and usage... At utility scale.
  - freemint 4y ago
    > If your house is still on-grid, you still have to pay all of the grid costs. Yes but building new solar causes new grid cost. > Because if batteries were a cost-efficient way to deal with solar's intermittent generation, every utility in the world would be tripping over itself to order batteries by the TWH. They are cost efficient in Germany. So i am not to familiar with other countries situation. > I also can't optimize my energy usage around the sun. With batteries you could do that more. Both have a role to play. Another reason for solar is that people rather invest $10000 in their house then $5000 in shares of a grid scale solar installation. So while it might not be capital efficient it unlocks more capital investment for the green transition. From an economic view roof top solar is a jobs program where well paying trade jobs are created all over the country.
    - vkou 4y ago
      Really? German utilities use batteries for day-night supply/demand smoothing? [1] How many GWH of capacity have they deployed? And isn't it the country where a KWH costs 33 cents? Given that solar produces electricity at ~2 cents per KWH, this seems pretty damning. [1] Are you sure you're not confusing this with minute-over-minute smoothing, which requires ~two orders of magnitude less battery capacity?