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Comment by hparadiz | Hacker News Reader

More like 40k financed over 7 years with a $500 payment. Except your electricity use goes into negative and you can recoup some of those costs. Meanwhile like the article said you start to use $400 worth a month and with batteries you end up fully self sufficient when the grid goes down.

Honestly on a tech salary it's a bit of a luxury but not much for the peace of mind of never having your power go out. Basically $120 more a month. And then when it's paid off it does become free.

If you own a home it's really a no brainer.

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My 21kw $52k system with a 26% federal tax credit costs me $270/month pre tax credit ($178/month after applying the tax credit to the principal), financed at 3.9% for 25 years (inflate that debt away!). There is a bill in Congress to restore the tax credit to 30% retroactive to the first of the year, and extending it 10 years further, possibly improving the economics if passed.

It was cheaper than my average utility bill, and my electrical rates will never go up as the cost of fossil gas burned by my utility rises. Any excess power I generate beyond what I consume my utility must cut me a check for at the end of year when we true up.

The credits and whatever feel like just-another-way to give money to people “lucky” enough to buy a house that they own-something that looks less feasible by the month for the majority, even making plenty, as rates and prices go up. And rent? Well, there’s a meme for that.

I can’t install PV panels even if I want to, but I certainly would not be doing it or even trying for a rental owned by an investment firm who would use it as an excuse to raise rates due to the improvements.

Community solar is designed to fill the gap you mention.

https://grist.org/climate-energy/bidens-under-the-radar-exec...

> and with batteries you end up fully self sufficient when the grid goes down.

My understanding is that the majority of installs are not capable (allowed?) to run when the grid is down. I do know that at the very least you'd need a transfer switch to ensure you're not backfeeding the grid when it's not expecting it, like with a generator.

Now that I think about it, I wonder if a generator could provide the reference signal for the inverters to synchronize against. You'd still be burning fuel at whatever the generator's idle consumption is, but that'll be less than actually using it for power.

Nah. It’s a standard feature of most battery systems to run when the grid is down. Solar without battery doesn’t, (and the solar itself cuts out) but if you have battery systems involved for storage, you’re already capable of them interoperating with the grid, or without it.

As for getting reference from a generator, no need. You can get all that from the batteries and they’re increasingly planned to be used for grid scale black start.

> My understanding is that the majority of installs are not capable (allowed?) to run when the grid is down.

Capable, IIRC. I seem to remember that you need to have a type of inverter that is quite a bit more expensive (several kilodollars) if you want to be able to run disconnected from the grid.

Most people opt for the cheaper inverter as there's not a lot of difference if you don't also have a battery storage system.

Most offgrid inverters have a generator input to which they will switch when you start the generator. If you replace the generator with the grid (and you have batteries) and the grid goes down they switch seamlessly to the batteries - well, within a fraction of a second, some applainces "blink". I am actually using this system as a sort of UPS for our office

The Tesla power wall has an optional huge contactor that isolates the mains power in the event of an outage. (which of course is an optional extra)

However the power swapover isn't seamless, so most computers will reboot.

That means that grid tied inverters can continue to function, but its not a UPS/

I suspect there are better/faster battery backup systems out there, but the the powerwall2 aint that.

I don't know there's any legal battery backup that's not "break before make". If there is I'd love to know what the operating principles are.

Could you have a parallel system that the house power switches to? Or even separate outlets to plug appliances into

Separate outlets means running cable that you won't use most of the time, and having to remember which outlets go to which circuit.

A transfer switch allows you to isolate and switch between two power supplies so that your house circuits are only ever connected to one of them, and the two supplies are never in the same circuit[1]. They can be had for a few hundred depending on the load[2].

[1] this is a break-before-make switch. There exist make-before-break switches for when you need uninterrupted power supply, but they're not appropriate for this case as you'd be backfeeding into the grid which is dangerous and illegal.

[2] https://www.lowes.com/pl/Generator-transfer-switch-kits-Gene...

Anyone can fortunately only make the backfeed mistake once, as whatever generator they backfeed will no longer exist after the connection is made.

There's no need for that. Turning off your main breaker in your panel will disconnect you from the grid and prevent backfeeding.

$40k seems very expensive to me.

In the UK for £17k you can get 7KW panels and a 13.5kWH battery, installed. That's approximately $21k

To use more battery than that you must be staying up very late!

I paid 60K, but it was 15 years ago. Half of the price was the structure that nowadays is not needed. Today the same installation but on a fixed roof + 20% power to offset inefficiency would cost me about 10K.

Yeah - I am going to do this asap.

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