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How are you calculating that? Solar installations are around $2.50-$3.50 per watt, so $20k would get you 6-8kW. Assuming actual output is 10% of capacity, that'

by ggreer 2y ago

How are you calculating that? Solar installations are around $2.50-$3.50 per watt, so $20k would get you 6-8kW. Assuming actual output is 10% of capacity, that's 14-19kWh/day or 5,000-7,000kWh per year. Current residential electricity prices in SF are 38.9 cents per kWh[1], so that's $2,000-2,700 per year in savings, or $40-54k over 20 years. The actual amount saved depends on how much electricity you're consuming during peak times, but I doubt that number is off by a factor of 10. 1. https://www.bls.gov/regions/west/news-release/averageenergyprices_sanfrancisco.htm https://www.bls.gov/regions/west/news-release/averageenergyp...

buckle8017 2y ago
I didn't calculate anything I just put in an address and a monthly electricity bill. https://sunroof.withgoogle.com/ https://sunroof.withgoogle.com/
- Retric 2y ago
  Ahh, ok the tool sucks it doesn’t seem to calculate based on your current cost per kWh or the local cost per kWh. It’s ignoring inflation on those calculations, acting like your electric bill will be the same in 20 years. It’s also ignoring residual value in the system after 20 years they typically last 25-30, and you don’t pay taxes on savings. There install estimates where also really high for my area, but I don’t know if that’s a general issue.
  - patrickhogan1 2y ago
    Your electric bill 20 years from now is just as likely to go down as it is to go up. In two decades, we could see advancements like mobile generators offering free power, ultra-affordable battery packs delivered to homes to meet energy needs, or even the widespread adoption of low-cost fusion energy. The key takeaway is that predicting the future cost of electricity is as challenging as it was to predict today’s solar energy costs—now far lower than anyone expected.
    - Retric 2y ago
      None of what you just said is even vaguely realistic. Prices can’t drop below zero but they can easily more than double, so even if you assume equal odds in either direction it doesn’t cancel out. Worse, any physical device is going to have a cost to produce it which requires charging people to use it thus they can’t even drop to 0. Beyond that none of their prices or timelines are accurate, even ignoring the issues with inflation.
    - bagels 2y ago
      When did PGE prices ever go down?
      - patrickhogan1 2y ago
        Neither option I mentioned would require PGE or a centralized entity. Both options would be off-grid.
    - throwaway2037 2y ago
      > mobile generators offering free power Wow, where is this magical place? I want to move there. :)
      - patrickhogan1 2y ago
        Mobile Solar Generator Feasibility With solar technology, powering a home with a mobile generator is possible. Yes, the generator and batteries will have associated costs, but the long-term benefits make it worthwhile. This assumes uninterrupted access to sunlight over the next 20 years without new restrictions. Key Considerations: 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 20 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 fits on most home roofs or could be mounted on a pole or hung through an apartment window. System Components: High-efficiency solar panels. 30 kWh battery storage for nighttime or cloudy days. An inverter to convert solar DC power to home AC power. Outcome: A mobile solar generator with advanced panels and efficient storage provides a sustainable and portable solution for powering homes.
- notatoad 2y ago
  sunroof was a 2015 project. if they haven't adjusted their cost estimates since they launched it, it could be wildly overestimating things.
  - gloflo 2y ago
    Same for panel efficiency https://en.m.wikipedia.org/wiki/Solar-cell_efficiency#/media/File%3ANREL_PV_Cell_Record_Efficiency_Chart.png https://en.m.wikipedia.org/wiki/Solar-cell_efficiency#/media...

by ggreer 2y ago

buckle8017 2y ago

I didn't calculate anything I just put in an address and a monthly electricity bill. https://sunroof.withgoogle.com/ https://sunroof.withgoogle.com/

Retric 2y ago
Ahh, ok the tool sucks it doesn’t seem to calculate based on your current cost per kWh or the local cost per kWh. It’s ignoring inflation on those calculations, acting like your electric bill will be the same in 20 years. It’s also ignoring residual value in the system after 20 years they typically last 25-30, and you don’t pay taxes on savings. There install estimates where also really high for my area, but I don’t know if that’s a general issue.
- patrickhogan1 2y ago
  Your electric bill 20 years from now is just as likely to go down as it is to go up. In two decades, we could see advancements like mobile generators offering free power, ultra-affordable battery packs delivered to homes to meet energy needs, or even the widespread adoption of low-cost fusion energy. The key takeaway is that predicting the future cost of electricity is as challenging as it was to predict today’s solar energy costs—now far lower than anyone expected.
  - Retric 2y ago
    None of what you just said is even vaguely realistic. Prices can’t drop below zero but they can easily more than double, so even if you assume equal odds in either direction it doesn’t cancel out. Worse, any physical device is going to have a cost to produce it which requires charging people to use it thus they can’t even drop to 0. Beyond that none of their prices or timelines are accurate, even ignoring the issues with inflation.
  - bagels 2y ago
    When did PGE prices ever go down?
    - patrickhogan1 2y ago
      Neither option I mentioned would require PGE or a centralized entity. Both options would be off-grid.
  - throwaway2037 2y ago
    > mobile generators offering free power Wow, where is this magical place? I want to move there. :)
    - patrickhogan1 2y ago
      Mobile Solar Generator Feasibility With solar technology, powering a home with a mobile generator is possible. Yes, the generator and batteries will have associated costs, but the long-term benefits make it worthwhile. This assumes uninterrupted access to sunlight over the next 20 years without new restrictions. Key Considerations: 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 20 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 fits on most home roofs or could be mounted on a pole or hung through an apartment window. System Components: High-efficiency solar panels. 30 kWh battery storage for nighttime or cloudy days. An inverter to convert solar DC power to home AC power. Outcome: A mobile solar generator with advanced panels and efficient storage provides a sustainable and portable solution for powering homes.
notatoad 2y ago
sunroof was a 2015 project. if they haven't adjusted their cost estimates since they launched it, it could be wildly overestimating things.
- gloflo 2y ago
  Same for panel efficiency https://en.m.wikipedia.org/wiki/Solar-cell_efficiency#/media/File%3ANREL_PV_Cell_Record_Efficiency_Chart.png https://en.m.wikipedia.org/wiki/Solar-cell_efficiency#/media...