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Comment by fyfy18 | Hacker News Reader

I was under the impression that - baring physical damage - solar panels won't just stop working one day as the article implies, but they merely decrease in efficiency over time. Most solar panels today come with a manufacturer's guarantee that after 25 years, they will still be 80-something percent efficient.

At this point they would have paid for themselves over many times, and would now be generating free electricity, so for most installations there is little point in replacing them.

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From what I understand all panels come with a 25 year warranty because that's the federally mandated minimum warranty, and that there are panels twice as old still operating today.

Unless they do something foolish like coat the panels in a plastic that degrades under direct sunlight, I don't really see why panels shouldn't last for quite a long time. Does the silicon itself take UV damage or something?

> Does the silicon itself take UV damage or something?

Yes, exactly that. Solar radiation causes crystal defects.

The last time I had an estimate for solar, the break-even was 18 years, so it made no sense whatsoever, financially speaking.

When you mention after 25 years they would have paid for themselves many times over, based on what criteria? I'd love to revisit this topic -- power costs in Florida are very high.

Edit: Just curious on why the downvotes? Not enough context? Negative sentiment? (not intended, genuinely curious about revisiting solar)

What is "very high"? Much of the reason it takes so long to payback is labor, permitting costs, etc. If you reduce or remove those costs payback is in the order of 5 years at 10 cents/kwh.

People will point out that it's silly to factor out labor and permitting but those costs drop radically on grid scale 10MW+ systems where as they make up nearly 50% of the cost on a household scale system.

Very high: for the hottest months of the year, power is $1100+/mo. Average for the last 24 months is just under $900/mo.

It's a larger 1-story home: we've tried to address insulation, low-e glass, and AC SEER ratings. Working and teaching from home = consistent cooling demands throughout the day, every day.

For someone from Europe that sounds insane.

It’s just as insane in the US. 10x higher than average in Florida and 30x my small apartment in Washington state.

Yes, but what is your per kwh cost?

That’s by far the highest residential power bill I’ve ever heard of anywhere. It’s 10x the Florida average!!

Either you have a poorly insulated 25k sqft mansion or your neighbors are siphoning off your power for an indoor weed farm.

Context: 5000 sf, 12' ceilings. 4 HVAC units. Large family, lots of animals, always at home, 9-10 workstations + 1 rack server running. Thermostats are set around 75-76F.

The first thing I'd be considering there is air leak detection, followed by a ground source heat pump. Having a bill that high implies on the order of 9000 kWh used per month, which is crazy.

The cost of solar has come down _a lot_ in the last few years. At this point the cost of a solar installation is dominated by the cost of the humans who have to deal wit the city to get permits and physically install the components on the roof. For a 6kw system (typical for a single family house in California) the cost of the panels is about $3000, the inverter is about $2000, the auxiliary components (racks, wiring, disconnect, etc) is about $1000. If you are doing it on new construction the install is basically free, but as a retrofit hiring a contractor that will work with the city to get the permits and install the panels is about another $1,000-$10,000 depending on who you talk to and how complicated the installation is (some people need a new electrical service for their house, which runs almost $5k in itself, etc)

That system should produce about 10,000 kw*hr of energy over the year, so the payback excluding installation would be under 5 years.

Thanks for this food for thought. I've commented a bit on costs in sibling threads.

Our home is relatively large (square footage and high ceiling heights compound that) and since we both work and teach at home, the cooling systems are in constant demand.

Appreciate the ballpark figures; time to revisit the idea.

> I'd love to revisit this topic -- power costs in Florida are very high.

Power /bills/ may be very high (due to hot/humid climate necessitating extensive air conditioning). But a quick google shows me power /rates/ in FL are around $0.11 per kWh - which is very low on a global scale (and on the low end of average for the US[1]). Solar costs are coming down on a per-kW basis, so the per-kWh electricity cost is the one you need to compare to find when it breaks even.

[1] https://www.electricchoice.com/electricity-prices-by-state/

The per kWh cost may be low, but the high humidity and heat = constant cooling demand.

We work and teach from home (pre-Covid) so the cooling systems are in use throughout the day.

This is my problem; my power is ~7.5¢/kWh; my walls are 12” thick (6x2 studs + drywall + facade), so my electric bill only runs about 120$/month, averaged. I have a 68$/month fixed flat hookup fee. That means I’ve got to get solar to “pay out” at ~52$/month.

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