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Solar panel installation costs, at least in the US haven't dropped in 15 years. It's still $25-30k to install 4kW-6kW worth of solar panels.

With the plugin solar I can imagine people in single family residential installing them on both sides of fences and gates to get an around the day benefit.

Also, with the price of solar panels decreasing below most (wood?) building materials with way higher durability, no paint required, why wouldn't it replace most sun facing siding applications aside from being "ugly".

> it gets popular enough to affect the grid,

The plug in solar systems are small and usually mounted in ways that don’t capture as much energy as the same panels mounted on a roof. These systems aren’t going to get popular enough to make a big difference in anything.

I think it’s nice that they’re available for people to do some small scale offsets, but I think they’re more of a gateway to better solar installations. They also send people down the path of investigating battery storage add-ons, which might actually be a better long term solution for everyone.

If we can get to a point where we can buy plug-in batteries that are subsidized by requiring coordination with the grid, the power companies could get distributed, controlled battery storage to work with their demand curves. This can already happen with the bigger permanent install batteries.

The biggest problem with plugging a generator into an outlet is you need a double ended cord. If you use everything correctly they work fine, but there are too many ways things can go wrong. The most obvious one is you plug everything in, start the generator, and the trip over the cord on you way back inside, thus sending the live male end flying toward you. Once in a while a kid will see these dual male plugs and plug them in - lots of ways things can go wrong here.

There is also the problem of backfeeding, but this is more theoretical - even if you know to limit your power use, your neighbors won't and so your generator will trip its own breaker. Linemen are taught to either treat power lines like they are live, or to short them to ground - it can happen they don't do this and you kill a linemen, but still not as big a worry as it is made out.

They make generator "inlets" that sidestep all these problems when used correctly. Most common I've seen is a block so you can't have the inlet and the main breaker both on at once.

The inverter box contains circuitry that cuts power output within some specified number of milliseconds if unplugged rendering the prongs "cold".

Fancy power electronics in them that make sure they only send power to the outlet while the grid is energizing it too.

In addition to the electronics that others mentioned, they also have limited amperage. That way even if you are pulling from your mains power and the solar at the same time, your circuit hardware shouldn't melt or catch fire.

These sync with the grid and also have safety mechanisms to avoid backfeeding if the grid is down (or it's unplugged).

There is no problem and so nothing needs to account for it. A split phase is just a transformer with three windings, and one is connected to the other. We call one side (high voltage) the primary, and the other two secondary, but the transformer doesn't care at all, it can send power either way (there are limits but we are well under the maximum rating of the transformer so we can ignore them). If you only draw 240 volts then the two connected windings act as a single secondary, if you only draw 120 then one of the two secondaries provides power. Any other combination - the transformer doesn't care.

U.S. homes typically get power through two hot wires. The hot wires are connected to a utility company's transformer and are 180 degree out of phase. Each supplies 120 volts.

The power from the plug-in outlet is consumed by any devices connected on the same circuit first. Any extra flow through the electric panel’s bar connecting the circuits on the same 120V phase, where the devices on them use the extra next. Any excessive power flows back out of the meter on the 120V phase line on your service connection to the transformer at the street block. The transformer might feed it to your neighbors. In any case the transformer feed electricity to the other 120V phase line back into your service connection, the meter, the panel, the other split phase bar, the circuits on it, and the outlets on them. The devices on the other split phase circuits technically are not using the plug-in power directly.

Most modern meters measure electricity going in and out on both split phase lines as a whole, as a net amount, so the electricity consumed in the other split phase circuits is offset by the plug-in power. However some old meters add the outgoing electricity up as consumption so you are paying for the electricity fed into the grid. Call your utility company to make sure.

Also, unless you have a net metering agreement with your utility company, you won’t get paid for any excessive electricity fed back into the grid.

I doubt it matters. The power company also theoretically has to deal with houses where they coincidentally draw more from one side of the split than the other. But I suspect it all averages out, and the contribution of a couple plug-in panels in a bunch of houses won't change anything.

It backfeeds onto the grid and becomes the utility companies problem to deal with. This is similar to them dealing with a house that is an unbalanced consumer between the legs.

grid forming inverters : )

I've seen setups where they put a 48v battery between the solar panels and plug-in micro inverter. No idea how this impacts efficiency or if there's any safety concerns though.

Yeah it seems like the inverter manufacturers don't see demand for that. I was thinking maybe the Victron Multiplus-II 2x120 could be paired for 240V output but I was wrong, that's only on grid power, it won't make 240V from battery.

Obviously the inverters and pairing technology exist, but I don't know where to buy one retail.

The Bluetti Apex 300 is an expandable 2.7kWh 3.8kW dual-leg battery + inverter + solar generator for ~$1000 (on sale).

The EG4 12kPV does 8kw split phase output and is $3k, but haven't seen anything smaller than that yet.

Yes, there are serious safety concerns. Both islanding, which is where a circuit is hot when it shouldn't be, and from a circuit overload.

Your circuit breaker protects your circuits by putting all the load (eg your microwave) on one side, and your supply (mains power) on the other. If too much load is present, the circuit breaker trips.

However, plugin solar puts invisible supply on the load side, which your circuit breaker cannot see. Let's make an absurd example so you can see what the problem is, then scale it back.

Imagine someone buys 5 panels that can each supply 5amps. They plug them into outlets on a 40 amp circuit. They then proceed to run their toaster, microwave, vacuum, and hair dryer. They can draw 65 amps through the wires before the circuit breaker trips. (40 from mains, 25 from the panels)

Let's say they had a good electrician who installed 6AWG wiring on that circuit, which is rated for 50 amps. The circuit breaker used to trip at 40, so no problem. But now up to 65 can go across the wires and suddenly you are exceeding rating for wires.

Now you might say, "most of these are 3.5 watts, and they clearly say don't use more than one". But I say that's a "good intentions solution". We should make it mechanically impossible to do the wrong thing. Maybe these panels could try to communicate over the electrical wires, and if they detect a signal from another panel they should self limit. Maybe we need to rethink circuit panel design. But as it stands people will absolutely buy one of these, decide they love it, and then buy 4 more.

These rely on seeing a grid frequency to follow when they output power. If you shut off the breaker for the circuit they're on, no grid frequency to follow, and they shut off their output. When unplugged, the plug never has any voltage on it.

These systems monitor for a loss of grid power and turn off when they detect an outage. UL 3700 is the standard, if you want to read more about it.

I wonder if they’re set up to cut off if the outlet has no power for exactly that reason.

They’d also probably depend on a power signal to frequency match.

Yes, it's designed so that total current and potential heat problems are still within safety margins of circuits built according to code. In most of Europe, one regular (or upper end of regular, depending on country) residential circuit can supply 3.6 kW (230 V * 16 A = 3680 W), so 800 W are "just" a 20% overload.

It doesn't have to be cheaper than utility-scale. It only has to be cheaper than retail electricity.

In other words, it can be useful even if it's not the most efficient way to do it. It only has to be more efficient than the status quo.

I don't have thd capital to build utility-scale solar. I do have the capital to install residential solar. My electricity is now cheaper.

There are advantages to distributed infrastructure as well! You mentioned one of the biggest disadvantages.

I am thinking along the line of:

  - You can just do it / upgrade it etc
  - Robust against central failures for various reasons
  - Resistant to those in charge of centralized infrastructure abusing their monopoly

Utility-scale solar might be cheaper but doesn't make my house resilient to grid failures. It also only benefits me when the grid is upgraded enough that ... well, it benefits me.

I'm sure it's cheaper to somebody. But with home solar, I can actually cut my power bill by a noticeable fraction.

It is easier to find a million people with a few hundred euros and a sunny balcony than finding one dude with a few hundred million euros and land on which building a solar farm is permitted.

Problem is for most of USA utility scale = utility profit for share holders.

For example Duke is for profit here in Florida, and charges about 25% more per KWH than OUC that is a public utility.

This leads to pricing where on one street your power bill is $250, but one street over its $200, often coming from the exact same power plant.

Last I checked the biggest cost in the electric bill is transmission, by a wide margin. Home generated power however small helps everyone.

Where I live we have Time of Day electricity pricing where the prices jump 2-3x during high demand. Panels conveniently produce the most power around this time, so this can save people money.

It's not and it will NEVER be.

Utility companies are not incentivized to lower prices because it means less money for them. Do you remember when power companies told people to conserve power and then people successfully did this? And then they raised rates because they weren't making enough money? This happens in California ALL THE TIME. I've lived here 30 years in Silicon Valley and it's the biggest scam that no one talks about. It happens with electricity and water. With water its even more egregious because they told us to conserve water because of the "drought" but once the drought was over, they raised rates because people weren't using enough water. My connection fee to water is over $100/month without spending a drop of water. That's why I stopped conserving water and water my lawn every single day because it turns out that my water costs are only about 1/3 of the actual water bill costs so fuck it!

It's the same playbook over and over again, there's no incentive to lower rates at all because it's an easy way to make money over an entire population of tens of millions of people.

Now PG&E is fighting to charge solar panel owners $100+/month just for the privilege of being connected to the grid. That would make having solar panels even more expensive than not having solar panels which is utter hypocrisy but no one seems to care or point this out. It's a complete and utter scam.

EDIT: I forgot to mention last year the rates were $0.37-0.45 per kWh, until this year when they implemented a base fee of $25/month, so they lowered it to $0.33-0.45/kWh. Rates in Nevada are 1/4 of that.

2015: $0.17-0.33 per kWh

2020: $0.24-0.38 per kWh

so prices have more than doubled in 10 years. Fucking criminals.

We should build now in anticipation of drone warfare. Utility-scale solar is easier to take out. Same as natural disasters.

The more stable you think the future will be, the more you want to capture the efficiency of central power.