My answers in color below.

In the end, it all comes down to Ohm's Law, where voltage = current * resistance and where power = current^2 * resistance.

The resistance of a given diameter wire is pretty constant (it can vary with temperature), so higher voltage means lower current is required to carry a given amount of power. When you have 250 kilovolt lines, it only takes 10 amps to carry 2.5 megawatts. If the resistance of a given piece of power line was 2 ohms, then carrying 10 amps would mean you've lost 200 watts. Going with a lower voltage, as would be required if we went to DC Not at all. High voltage DC is quite feasible.
, means much higher resistance losses unless the distances and currents involved are kept low, such as with many decentralized power sources. No, I do not favor decentralized sources.

There was a good discussion of the problems with decentralized energy production on this blog earlier this week. He also has a good discussion on the problems of most attempts to convert to large scale use of alternative energy. The author did mention that a significant percentage of the energy introduced into high tension powerlines are lost in transit, but not as much as some people believe. But DC losses are significantly smaller because of the absence of reactance losses and corona losses.

Power generation is subject to considerable economies of scale, which is one of the reasons why the existing power generation system relies on fewer big plants instead of a swarm of small ones. Per unit of power generation capacity, big plants cost a lot less than small ones do. Very true.

But what's more important is that they are also are more efficient.Also true.

Distributed small power plants would reduce transmission line losses by reducing the distance the power was transmitted. But those losses are not as major as David thinks, and small plants would be less efficient in producing electric power. You would lose more than you would gain. The overall result is worse, not better. That's especially true when you're comparing power generation over ranges varying by 6 or 7 orders of magnitude (i.e. a 1 kilowatt generator for a single home compared to a 1 gigawatt power plant). I think that you misunderstand my argument. I was favoring High Voltage DC transmission in order to improve grid stability.

Utilization of energy means taking advantage of energy differences. There's an inherent energy difference between a high place and a lower one, and there's inherent energy difference between a warm place and a cool one. The laws of thermodynamics tell us that the amount of energy which can be converted to useful work is a fraction of that difference, irrespective of the absolute energy levels of each.

We take things from the high place and move them to the low one in a fashion which permits us to harness some of the energy release to perform work, and that's how hydro power operates. Hydro is actually a form of solar power; sunlight powers the weather, which moves water from the ocean to the mountains. As that water flows downward again to the sea, we use some of the energy which is released as it falls. OK

Likewise, we move heat from the warm place to the cool place and likewise harness some of it, and that is how a coal or nuclear power plant operates. (In a sense, coal is also a form of solar power, and nuclear arguably is too, but let's not get into that.) OK

Up to a certain point, the greater that differential, the more efficient a power system can be at harnessing it. A greater differential means there's more energy present in absolute terms, but it's also possible to utilize a larger percentage of the energy; it's a squared advantage up to the point where efficiency gains begin to level off. True for THERMAL conversion, NOT for mechanical conversion. Theoretical (but not practical) conversion efficiency for hydroelectric power is independent of height.

In hydro the term for that difference is "head". The head is the distance from the turbines up to the surface of the lake behind the dam. If the head is not very great (e.g. 2 meters) then there isn't very much energy available per unit of water processed, and the percentage of the energy which can be harvested will be relatively low. Again, the efficiency of conversion is independent of height.

With that kind of head, you can't use turbines at all. Pure nonsense. Two meters can be used quite well by a small turbine. There are commercially available turbines designed to use such small pressure differences. Admittedly, they are not very efficient, but they work.
There isn't enough pressure; the water moves too slow, and flows through the turbine and around the blades without applying enough pressure to the blades to make them move. With that small a head you have use something like a water wheel. A water wheel works with low head but doesn't scale up, and is inherently less efficient overall than turbines operating at optimum conditions. (Also, turbines scale far better for volume of water processed.)I admit that such turbines are not very efficient.

As the head increases, the pressure differential across the turbine goes up, and turbines harvest more of the energy with less being wasted as turbulence. (Understand that this is far from a complete discussion of the factors involved; there are other ways in which turbine efficiency rises with speed and pressure because of non-linear scaling e.g. bearing resistance as a function of speed, or non-linear characteristics of fluid flow.) So up to a certain point, the greater the difference between the "high place" and the "low place", the more efficient the conversion will be.

There are also some economies of scale associated with volume; when more water is used, there are ways in which efficiency improves. OK

A bigger energy differential also helps heat engines such as boilers and steam turbines, which can become more efficient as the temperature difference between the "warm place" and "cool place" increases.

Big dams usually have more head than small dams. Big heat-engine power plants usually run at higher temperatures.

You could make a small heat-engine plant use the same temperature differential as a big one, but there are other scaling factors, and the overall efficiency will still be worse. One such scaling factor is known as "cube-square", and in this case what it means is that the heat loss of a boiler is proportional to its surface area, which rises as the square, but the energy production capacity is a function of the volume of the boiler, which increases as the cube. If you double the size of the plant, there's four times as much surface area but eight times as much volume, so each unit of energy generation volume suffers losses through half as much surface area.

It turns out there are also economic reasons for gains in economy of scale because the cost of some things don't scale linearly with their size or capacity. There are things you can include in the design of big plants which help improve their efficiency which don't make economic sense for small plants.

And there are some kinds of approaches which don't work at all below a particular level; you do them big or you don't do them.

Those are just some of the technical reasons why distributing power generation is not helpful. There are also economies of scale in costs. For instance, you need fewer employees per unit generation capacity to operate large plants than to operate small plants.

And implementing such a change would take decades, because the turnover of capital plant is really slow when it comes to this kind of thing. After the blackout fiasco, the move to DC transmission should be pushed hard.

Let's not even talk about the regulatory hurdles involved in trying to get approval to build hundreds of small power plants close to end users, all of whom know lawyers. Again, I am NOT for small power plants.

There is an idea that he didn't discuss that might merit some consideration. One day, it might be more efficient to ship something like hydrogen gas (even thought there would be losses there, too) that could be used to operate fuel cells of in situ production.