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Do you even actually save money, accounting for the financing and installation of the solar panels? A while back there was a thread on the SolarCity subreddit

Do you even actually save money, accounting for the financing and installation of the solar panels? A while back there was a thread on the SolarCity subreddit linked from HN where the OP discussed his savings thanks to nice weather, but still figured he had a 20 year payback period on his setup. That is crazy.

dylan604 3y ago
I never even suggested solar. I just want a battery pack that charges when grid prices are cheap, and powers off battery when grid prices are high. Complicating it with solar is beyond the scope of the original intent.
- 0cf8612b2e1e 3y ago
  That seems like it would be hard to ever make a financial return. Say a battery costs $10k and a home uses $100/ month electricity. If you assume electricity is free at night to fully charge the battery and meet energy demand, that’s 100 months (8 years) to break even. Real world costs are going to make it quite a bit worse than that.
  - dylan604 3y ago
    As they say, "location location location". In a Texas summer, it is easily 3x that per month for 4 months out of the year for a house. So, that's 12 months in one quarter based on your math. The vast majority of that is just running the A/C. So again, this makes much more sense when you look at the nuances vs just some lame internet posting of using averages. If it makes no sense for you, that's too bad, but to come out with broad brush comments alluding to it not making sense ever is just naive.
    - 0cf8612b2e1e 3y ago
      I guess you could further insult me or provide your own napkin math. Sure, let's say the summer months bump the Texas electric bill to $167/month (8$100 + 4$300). The previous model was assuming free electricity. My quick search is revealing that using differential pricing in Texas, the difference from the normal rate (~$.16) and the low rate (~$.08) saves ~$.08/kwh. Assuming you could perfectly offset all usage onto the cheap rate, that would yield a monthly savings of $83.5. Which yields a $10000/$83.5 = 120 month or 10 year payback period. Then again, we forgot to right size the battery system. This site[0] claims an AC is going to use 16kwh/8 hours. A Tesla Powerwall is 13.5kwh. If you want the battery to fully cover your AC needs alone, you will need at least one additional battery system. Naturally, we are missing out on maintenance, opportunity costs, grid connection fees, potential rebates, etc, but I think we have indeed landed on a more nuanced model. [0] https://learnmetrics.com/how-much-electricity-kwh-do-air-conditioners-use/ https://learnmetrics.com/how-much-electricity-kwh-do-air-con...

dylan604 3y ago

I never even suggested solar. I just want a battery pack that charges when grid prices are cheap, and powers off battery when grid prices are high. Complicating it with solar is beyond the scope of the original intent.

0cf8612b2e1e 3y ago
That seems like it would be hard to ever make a financial return. Say a battery costs $10k and a home uses $100/ month electricity. If you assume electricity is free at night to fully charge the battery and meet energy demand, that’s 100 months (8 years) to break even. Real world costs are going to make it quite a bit worse than that.
- dylan604 3y ago
  As they say, "location location location". In a Texas summer, it is easily 3x that per month for 4 months out of the year for a house. So, that's 12 months in one quarter based on your math. The vast majority of that is just running the A/C. So again, this makes much more sense when you look at the nuances vs just some lame internet posting of using averages. If it makes no sense for you, that's too bad, but to come out with broad brush comments alluding to it not making sense ever is just naive.
  - 0cf8612b2e1e 3y ago
    I guess you could further insult me or provide your own napkin math. Sure, let's say the summer months bump the Texas electric bill to $167/month (8$100 + 4$300). The previous model was assuming free electricity. My quick search is revealing that using differential pricing in Texas, the difference from the normal rate (~$.16) and the low rate (~$.08) saves ~$.08/kwh. Assuming you could perfectly offset all usage onto the cheap rate, that would yield a monthly savings of $83.5. Which yields a $10000/$83.5 = 120 month or 10 year payback period. Then again, we forgot to right size the battery system. This site[0] claims an AC is going to use 16kwh/8 hours. A Tesla Powerwall is 13.5kwh. If you want the battery to fully cover your AC needs alone, you will need at least one additional battery system. Naturally, we are missing out on maintenance, opportunity costs, grid connection fees, potential rebates, etc, but I think we have indeed landed on a more nuanced model. [0] https://learnmetrics.com/how-much-electricity-kwh-do-air-conditioners-use/ https://learnmetrics.com/how-much-electricity-kwh-do-air-con...