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Comment by ChuckMcM | Hacker News Reader

It is funny because we get cold called by these folks probably twice a year, and once a rep came up to our house and wanted to tell us about solar, so I gave them a short tour of the 5KW system we installed 15 years ago. The one that has literally paid for itself (about half way through year 11) based on actual generation and power consumption statistics. It would have paid for itself sooner except that PG&E has twice updated the grid tie rules which have incrementally reduced the benefit of rooftop solar.

The TPO systems as described are a boon to PG&E who, if you can believe their actions, is really concerned that people will just drop off the grid altogether.

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Even without explicit subsidies, it seems like rooftop solar is still getting hidden subsidies? If homeowners were paid wholesale rates for the power they provide, with prices based on the spot market, would any of it make sense financially?

No, it wouldn't. For the same reason that me operating a coal power plant in my backyard wouldn't provide me with cheaper electricity then just buying from the grid.

A centralized utility, even a poorly run one, will always provide electricity safer, cheaper, and more consistently then thousands of tiny private installations.

Counter example: PG&E. More expensive than smaller, greener alternatives. And 85 people killed just last year alone is the safety record.

PG&E provides ~100 TWh of electricity/per year.

Rooftop solar kills ~1 person per 2 TWh of produced energy. Mostly from people falling off roofs.

If you were to look at the big picture, and not one outlier year - and look at the entire past decade, PG&E will probably have a better safety record.

Also, if you want to do fair accounting, you can't solely blame PG&E for California wildfires. The entire state is a powder keg - and they just happened to be the last people who touched it. It would have burned sooner, or later.

If your horse bolts from a barn, because there is no barndoor, do you blame the last person who went into the barn? Sure. Are they the sole point of blame? No. Especially if your barn has a history of horses bolting from it.

I like this argument but I disagree with it.

I will stipulate that PG&E qualifies as a 'poorly run, centralized utility' and based on its billing it cannot provide power to residential homes for less money than a locally installed solar system can.

The reasons for this are worth considering.

PG&E has to maintain a power transmission infrastructure. That infrastructure has a high inspection cost, land use cost, equipment costs, and insurance risk cost (witness that the threat of the being found liable that their transmission line maintenance (or lack thereof) contributed to the most expensive wild fire in CA history).

Then there are the externalities which we don't account for as much in either scenario. Whether it is the cost of scrubbers on a coal plant, the waste storage costs of nuclear, or the gas pipeline infrastructure for natural gas plants that leaks methane into the air.

What solar does it centralizes the manufacture of the energy production equipment with finite externalitie. It provides highly granular capacity that can be deployed without large step wise changes in capacity (this is the 'nearly unused plant' problem where you have to run a plant because the instantaneous need occasionally exceeds your current generate capacity while the average need is staying below that level (this is where Teslas battery farms help energy companies cut costs).

So when comparing systems dollars to systems dollars, Solar with the current economics of about $3.25/watt installed is actually cheaper than poorly run centralized power plants.

Oh, don't get me wrong - solar power generation is fantastic in areas that can support it (Which is most of the world.)

Rooftop solar power generation is what I have an issue with. Utility-scale solar has all the advantage that you cited, without the disadvantages of being incredibly labour-intensive, overcomplicating the electric grid, and offloading long-term maintenance to non-experts.

If you are going 100% off-the grid, then yes, local installations may be cheaper (Because they don't include the cost of maintaining the grid.)

However, you'll still have to maintain a national grid - because not all buildings or businesses have the rooftop capacity, or the hundreds of thousands of dollars in capital to install enormous battery blocks.

So, what ends up happening, is that a few people drop off the system, and raise prices for everyone else - including people who don't have the option to drop off the grid. My building, for instance, houses 40 units. It has four times the rooftop capacity of an average home. No amount of battery storage is ever going to let it be grid-independent. Other residences dropping off the grid, completely, just shift costs around - they wont reduce overall costs.

It requires a grid, but maybe not a national grid?

There has been a lot of talk about how we need more long-distance power lines for load-balancing solar and wind. However, the PG&E bankruptcy seems to show that we've been underestimating what it takes to properly maintain a grid. Are long-distance power lines more expensive than we thought?

Or maybe rural, fire-prone areas would do better with more local solutions that reduce the amount of low-usage power lines that need to be maintained?

PG&E is a pretty poor strawman for anti-grid arguments. CA pays 2x what neighboring states do for electricity, and despite having mild weather and high population density have unreasonably high levels of safety and reliability issues.

It’s probably second only to Puerto Rico on that front, at least in the US.

Having said that, I’m eagerly awaiting the day I can disconnect my house from the grid, and close my account with them.

It's interesting that you say this because I've had the same feeling. However, I'm still quite hopeful for rooftop installation simply because from a societal point of view it's a better utilisation of land. Where I live we have really ideal conditions for both solar and wind and while I'm relatively happy dotting every hilltop in this area with wind turbines, they've been clear cutting the forest, paving it over and carpeting it with solar panels. I realise that we're going to need some of this, but I would really like to minimise it as much as possible and I'm willing to pay for it. It frustrates me no end that at the same time they started pushing renewable options, they deregulated power sales and capped the distribution costs for the power company in our area. So while the costs of running the grid goes up, they have have no leeway in increasing prices to match. Sigh... I sometimes feel I'm going to be living in a literal silicon valley at some point... The irony, of course, is that I live in Japan and while we have oodles of geothermal potential, it's still a politically sensitive option to even experiment with (for fear of disrupting the hot springs -- lots and lots of money tied up in that and already people complain about the drop off in temperature due to over use...)

For 6-7 hours on most days, rooftop solar can provide power to residential homes more cheaply than PG&E.

For 12+ hours a day, PG&E is almost certainly cheaper I believe.

You cannot just look at $/MW costs when the goal is to have 100% generation adequacy (i.e. demand is uncontrolled, people can turn on loads within their home whenever they want and always expect to have adequate supply).

If loads are interruptible and you don't mind not being able to turn on your air conditioner at 10pm on a hot summer night, then sure, off-grid rooftop solar can be cheaper. Primarily, the way people who actually live off-grid operate is the same way people without running water wash dishes: you ration your consumption.

But most people want power for all their stuff, all the time. It will always be easier to plan for generation adequacy and resiliency centrally rather than every single power user having to install enough generation and storage to meet their own needs, 100% of the time.

Totally agree that it's easier to plan a centralized system over a decentralized one, provided that you adequately fund people to maintain all the components. (And trim trees!)

But have you ever been in a power outage, used your cell phone as a flashlight, and thought, "man, I wish my entire house ran off of a battery like my cell phone?"

A home builder already plans for 95% generation adequacy of hot water -- they literally find space in the floor plan for a hot water heater, and decide how big the tank should be. If you run out, either you ration usage or you buy a bigger water tank.

If home batteries had the right safety-energy density ratio (admittedly -- hard problem; see the RFS for Energy), you could just include one in the floor plan based on 80%ile usage, like the batteries in laptops, and cell phones, and electric cars. They're just too big and expensive now.

Define safer? more safe for an individual or more safe methods of generating power?

Centralized utilities also have a nasty issue of not coping with natural disasters particularly well...

A centralized utility, even a poorly run one, will always provide electricity safer, cheaper, and more consistently then thousands of tiny private installations.

Not necessarily. For household solar, economies of scale kick in at the manufacturing level -- if you’re producing lots of standardized units, each household’s installation costs can go down.

You’re right that there will be some distribution inefficiency, as some households will over-produce and some under. But it may not be that bad if most households size their installations sensibly.

The centralized utility can balance distribution across many households, but there are some extra costs too -- installation and maintenance of power lines, power leakage, downtime due to faults.

Edit to add: I suspect we could agree that district solar (small local utility companies) is an excellent compromise that gets most of the benefits of both types.

Maybe? A well-ran local utility is likely to do a better job then a poorly-ran large one.

Unfortunately, how well a business runs is not always correlated with size.

More efficient to produce a certain kW figure, but run for profit and at the cost of freedom for the consumer.

There are hundereds of different subsidies in the US across all the different states. Some vesting over time, valid from day x to day y, and all kinds of other scenarios. It's really complicated, but chances are high that there is a subsidy or grant somewhere you could take advantage of.

How do you calculate savings at the 11-year mark? If you'd invested the same amount in index funds over an 11 year period you'd see your money double in an approximately 10 year period.

We have kept records of the power we've consumed, the power we've generated, the cost of the system and the cost of repairs/maintenance (one panel and one inverter so far over its lifetime).

For the financial analysis we assumed the money would be committed to paying for power one way or the other, there isn't really an option for putting it aside in the mutual fund so the 'invest' option was off the table. With the use of a current measuring system[1] we also have time of day usage numbers which is an option that helps people who aren't home during the day. In our case there is always someone in the house so the tiered rate metering was the only rate schedule we needed to consider[2].

With this information we can calculate the total money would would have spent just paying for power from PG&E and making no change, to the money we spent on the system install ($20,000) and the subsequent money we paid to PG&E for power and for their meter reading service. A bit more than 11 years after the install the total money spent over the period was less for the solar option. Our current annual electricity spend is about $420 (that is $120 for their meter reading + about $300 in additional KWh of energy above what we generate) vs roughly $3000/year or average $250 a month. Effectively $2600 a year is not being spent. If I were a min-maxer then I'd be putting that money into a mutual fund and it would start compounding and well, then the difference would start to look ridiculous.

[1] "The Energy Detective" -- http://www.theenergydetective.com/

[2] While it is true we could have changed further things about our lifestyle to fit into other rate schedules that avenue wasn't pursued.

It's worth modeling the cost of capital of your system to provide a fair comparison. Assuming the it lasts 20 years before you need to replace it entirely and after maintenance you save $2600 a year ($217/month) then what rate of interest could you pay if you took out a loan to cover the initial capital outlay?

Plugging the figures into: https://smartasset.com/personal-loans/personal-loan-calculat... and adjusting the interest rate slider you get a monthly payment of $217 when the interest rate is 11.75%. That's a pretty good rate of return for your investment. Not ridiculous, but solid.

$250/mo is a pretty generous number to compare against. Our >2500 sqft house averages under $100/mo. With the fairly extreme heat we have in in Texas, and A/C set to frigid while we’re home our bill _peaks_ at ~$150 in August. Well..that’s after a $1000 investment in attic insulation the first month we moved in.

Do you keep track of your KWh per month? If so, consider reading this page: https://www.pge.com/en_US/residential/rate-plans/rate-plan-o... and then plugging in the numbers. That will give you an idea.

For my house in Nov of 2014 the tiers were Tier 1: 15 cents/kwh Tier 2: 18 cents/kwh Tier 3: 26 cents/kwh Tier 4: 32 cents/kwh

And the baseline allowance is 10KWh a day (our house typically uses 24 - 28KWh per day.

Put those numbers in to your power bill and tell me what the number comes out to.

What I mean is that your initial outlay either needed capital or a loan. This is money that could have been invested, with electricity bills taken out of that kitty. What's confusing me here is that you've said you've been saving $2600 per year in electricity costs but it took 11 years to save $20000 off your bills. Either you've averaged about $1800 per year in savings or you've spent more than $20k on the system + maintenance, or I'm missing something. Was there some sort of tax offset here to make it more cost effective?

The point I was trying to make is that a dollar spent 11 years ago isn't the same as a dollar spent today.

Thanks for that clarification, we did in fact finance the initial capital, we were re-doing the roof and as part of that we chose to refinance the house to take advantage of the lower interest rates. And yes, there were government rebates in force at the time, the actual system cost was closer to $40,000 but our part of that bill was half or $20,000. FWIW the refinance which only added the cost of the roof and panels to the balance and reduced the interest rate left us with a smaller monthly payment with a similar pay off date (replaced a 30 yr fixed with a 15 year fixed)

As for costs, maintenance included replacing a failed inverter, that was $3500, and a panel, that was $450. The way in which electricity has also changed, when we started it was just kilowatts in vs kilowatts out annual true-up, they dumped that and switched to time of day, but changed their mind when the economics didn't work out for them, and now they are on the tiered system. They also blew up the town of San Bruno and convinced the PUC that they should be allowed to raise rates to cover their costs, so the price of electricity has gone up. Net result is that we didn't save as much per month when we started, incurred maintenance costs above the original $20K, and PG&E has changed the rules several times on how the accounting works. Fortunately all of that complexity can be factored out just by computing the bills vs what we paid.

PG&E who, if you can believe their actions, is really concerned that people will just drop off the grid altogether.

It is.

It just looks to the east where nearly all of the largest commercial energy consumers in Nevada have dumped NV Energy and built their own solar farms to save money.

Did they try and sell you anyway?

Thankfully no. But they haven't seemed to have deleted my number from their phone number list either.

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