> It only makes sense if the EV owner can somehow get charge capacity "for free"
The EV owner has the power electronics 'for free' - ie. they have almost infinite lifespan, and just a capital cost.
Additionally, the variations of energy prices on the grid are really wide. There might be $100k/MWh for 5 minutes per year. It isn't worth a static operator paying the capital cost for the batteries (which also degrade with time) to setup for 5 minutes use per year. But it does make sense for the EV owner to do so, because his marginal cost is tiny.
This depends where you live and the size/efficiency of your rooftop setup, right?
If you completely neglect the installation part, sure. Utility-scale solar farms have massive efficiencies of scale on purchasing panels and on labor-related overhead.
It's not that clear cut, basically.
I think what the EV model allows is for private car owners to essentially sell a part of their car back in increments, if for some reason their driving behavior changes and they don't need to drive as much as they used to.
If someone builds that storage facility to do it commercially then great.
> rooftop solar can't exist without special subsidies
Yet it does
https://www.seia.org/initiatives/solar-investment-tax-credit...
> The solar Investment Tax Credit (ITC) is one of the most important federal policy mechanisms to support the growth of solar energy in the United States. Since the ITC was enacted in 2006, the U.S. solar industry has grown by more than 200x - creating hundreds of thousands of jobs and investing billions of dollars in the U.S. economy in the process.
The Section 48 commercial credit can be applied to both customer-sited commercial solar systems and large-scale utility solar farms. The rate is effectively at 30% until Treasury issues guidance on new wage and apprenticeship standards. Two months later, the rate will be at 6%, with an additional 24% (for a total of 30%) available for meeting these new labor standards.
So utility-scale solar farms can get the same 30% credit as rooftop solar. They're both tax-advantaged compared to (e.g.) building a new gas plant, but the rooftop credit isn't any higher, at least not on the federal level. Self-consumption from rooftop solar may avoid other taxes, like sales tax, but in many states there is no sales tax on residential electricity to begin with.
It's part of the "Inflation Reduction Act of 2022" (and at a higher rate than before): https://www.solar.com/learn/inflation-reduction-act/
Rooftop solar is heavily subsidized almost everywhere it’s popular. Rooftop solar isn’t a good deal for utilities or their non-rooftop-solar customers.
I say this as someone who lived off the grid on solar for years; encouraging rooftop solar may have kickstarted the learning curve for the solar panel industry, and as such may have been pretty good social policy.
But it definitely owes its existence to subsidies.
These days grid scale solar makes lots of sense, rooftop solar still doesn’t (and the subsidies are now harder to defend).
Plug in the numbers. A charge cycle is probably around 200 miles (not even optimistic). That means that 1000 charge cycles is 200000 miles. That's roughly the lifetime of a car. However, I have heard anecdotes that EVs should last longer, due to a simpler transmission, so this may be a little up in the air.
I already have to own a car for short trips most days and an occasional long trip. And when I'm not going on a long trip I have a lot of extra battery capacity that I can rent to the grid at extremely low (additional) cost to me.
A dedicated battery storage facility on the other hand has to justify the entire price of the battery.
A real deployed algorithm would estimate the "degradation cost curve" over the entire DoD, and stop charging when total (fully-considered) costs exceed revenue.
That milestone has been hit in some places Australia already.
If the system still depends on distribution, someone has to pay for it.
It may be that rooftop solar users will be asked to pay more for that distribution than they think is reasonable.
I’m sure not excited about my grid operator proposing a $50/month minimum for electricity, it makes my panels seem worthless. But there is logic; I was being subsidized by net metering. And in future I may have to pay a cost closer to the true cost of access to the stability of the grid.
If you can really treat the whole cost of the battery as X cents per charge cycle, disregarding the lifetime of the car/battery, this won't work at grid scale. Someone else will build a storage facility that just charges and discharges batteries, and they will outcompete rational EV owners, because they will have economies of scale and battery banks designed for this use. It only makes sense if the EV owner can somehow get charge capacity "for free" - eg the car will be EOL after 1000 charges but the battery lasts 2000 - he should sell the extra 1000. Or alternatively if getting 8c now is better than getting 1 charge in several years time (plausible if interest rates, energy futures prices etc are right).
However, this could be wrong. The same logic says rooftop solar can't exist without special subsidies, and a lot of people disagree with me there.