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Comment by kshacker | Hacker News Reader

I do not want to fight with the utility or the insurance for such work, but this made me think: Can I set up something (I have a house) in my backyard + frontyard to just charge my EV? Catch the sun when it can, and then charge the car when connected. My PG&E bill says 56% of my usage is from midnight to 6 AM which is just EV + fridge. Although I pay a low rate on that, but imagine dropping half of your usage.

I specifically pick out the EV as an example because by definition my system would never need to connect to the house or the grid, so I guess all I have is a disconnected battery (powerwall) to insure.

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You _can_ do it, but EV charging is a big load for a few hours. That's not really what solar is good at. Solar likes smaller loads spread throughout the day.

If you go super cheap (the "$1000" system in the article), you'll be able to put a couple miles into the car in the afternoon on "level 1" charging. It's not nothing but it's not really practical for a car (but probably fine for an electric bike/moped). Also, most of the available power is unused since the battery is so small.

So you get a battery big enough to hold everything your panels can generate. You get a more powerful 240V inverter, a nice 8-10 kWh battery, and move to Southern California. With the best possible circumstances in July, you can fill up that battery every day, and add 19 miles to your car overnight.

Now you're at $10,000 for about 6,500 miles per year.

If the battery lasts 8 years (LFP can do 3000 cycles, 1 cycle per day = 8.2 years), you're paying 19¢/mile (and only if you use all of the power you generate).

Compare that to just plugging into the wall, which is 3-6¢/mile.

I would argue those prices a bit. A pair of 5kWh rackmount LFP batteries is only about $3,000. Assuming you're charging overnight, you can definitely get by with a 120V inverter like OP. Get a charger that does NEMA 5-20 for 16A and it'll transfer 10 kWh in 5 hours overnight fine.

I agree with your conclusion that wall is better though.

You might consider something on the opposite end of the spectrum, specifically net metering. If your grid connection is reliable, it's even more economical to get a solar system without batteries that feeds the grid. Where I'm located people pay the difference between the two without regard for when the power was generated or consumed. It also means your system is more efficient because there are no battery losses.

Net metering is no longer available in PG&E territory.

All the information I can find indicates that it remains available for new hookups. Of course, since April 2023, new hookups are under NEM 3.0, which is significantly less beneficial to the generator than earlier NEM programs.

NEM 3.0 isn't net metering. It's net billing, where exports get credited at wholesale rates.

how ass backwards

If you look at CalISO graphs, solar is very dominant already to the point where there's consistent energy exports during daytime.

Why would they want to incentivize more grid attached small solar at this point?

I’ve been considering this for my home. I have solar already but with an EV my usage exceeds my generation. Second hand panels like this ones in this article are cheap. I could get a set of those and sting them into an EcoFlow Ultra which has the solar inverter and ~5kWh battery. Then plug an EVSE directly into the 240v plug on the eco flow. Eco flow also has an API so I could get fancy with the software and change what gets charged based on the car or battery charge levels.

It would cost ~$6K. I estimate I’d save about $1500/yr from my electric bill. ROI isn’t great but most home projects have an even worse ROI so I still might do it just for kicks. Would also be nice to have a big Eco Flow battery I could use for other stuff.

Yes very easy with a ground mount with 4 panels, a battery and inverter.

I should write an article about it because I had planned to build something myself and keep all equipment outside and build a small wooden enclosure away from the house for it.

My EV lives outside & right beneath the only safely accessible part of my roof to put solar on... so an explanation would be grand! My only issue is that I need solar->battery->car, as the car is at work 3/7 days...

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