Comment by SwellJoe | Hacker News Reader

Comment by SwellJoe | Hacker News Reader

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Yes. Even without subsidies, a grid-tied solar power system will pay for itself well within the lifespan of the cells (the lifespan of solar panels is 25-50 years). A battery-backed "off the grid" system is not there yet, because the batteries are expensive. How soon it pays off will depend on how cheaply you obtain the panels and how much you pay for installation; these vary wildly depending on the location and vendor.

I did my own solar installation for about $1000, and it's enough for me to live lightly on (no AC, no microwave, no electric heater, but laptop and phone and hotspot stay charged, and fans can run indefinitely). Fridge runs on propane, when I'm off-the-grid. I'd need to quadruple that to turn on the AC or electric heat for any length of time, and would need a lot more batteries (I have three group 27 deep cycle batteries and a 3000 watt inverter).

Anyway, I got sidetracked a bit. We're currently at the point where a DIY installation can pay for itself in under 9 years. Maybe even as little as 7. Professionally installed systems, with subsidies, are probably around the 10 year repayment mark. And, the panels get cheaper every time I look into it. The batteries stay pricey, though.

I'm also off the grid, and fortunately it's sunny now so I can write this message :)

Can you please explain what kind of batteries are you using?And what are your usage patterns? For example I'm using two 12V 200A lead batteries, I'm trying to use then only on 30% discharge so that they will last longer.

I have three Interstate group 27 deep cycle marine lead acid batteries. They are rated for 65 amp hours (more at lower amperage draws...which is why having more batteries is helpful); which is enough to where I almost never have to run my generator, unless it rains for a couple of days.

They're nothing special, just heavy as hell lead acid batteries. I also try to never discharge too low...my rule of thumb is 50%, though I've run them until the inverter shut off due to low power. So, I've obviously gone below 50% a few times. They're three years old, and starting to show signs of degradation. I bought them at Costco for, I think, $98 each, and I'm pleased with the return on investment, given that they've gotten me out of being stranded on more than one occasion (I'm in a motorhome, and the chassis battery has been an interesting component, having more than it's fair share of failures, always in very bad places to have a motorhome that won't start).

I should point out that when I am off-the-grid, I am extremely conscious of my power usage. I charge everything during the day, religiously, so that I don't even have to turn the inverter on, some nights (lights, fans, water pump, and fridge igniter are 12V). It's a ritual...actually, it's a really satisfying ritual that I miss when I'm living plugged in. I need to go get lost in the desert or in Mexico this winter; been parked too long.

Is that lifespan number a conservative estimate? Solar panels are just high-purity silicon (simpler than drywall, as Musk puts it), what can make them stop working?

Yes, that is a conservative estimate. The warranty on my Sharp panels is 25 years...they are expected to last longer. Though, as I understand it, the output of panels does degrade over time; I don't know by what mechanism that degradation happens. And, there are electronic components in the whole configuration that may not last forever due to corrosion.

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