[NeilBlanchard]

Hello again,

Here's the page I found that states losses can be up to 30%:

The Physics of Everyday Stuff, by Sam Hokin

High-Voltage Transmission Lines

So we now finally come to the topic of this page: the transport of large amounts of electrical power over long distances. This is done with high-voltage transmission lines, and the question is: why high voltage? It certainly has a negative safety aspect, since a low voltage line wouldn't be harmful (you can put your hands on a 12 V car battery, for example, you won't even feel it; but make sure you don't put metal across the terminals, you'll get a huge current and a nasty spark!). Electric energy is transported across the countryside with high-voltage lines because the line losses are much smaller than with low-voltage lines.

All wires currently used have some resistance (the development of high-temperature superconductors will probably change this some day). Let's call the total resistance of the transmission line leading from a power station to your local substation R. Let's also say the local community demands a power P=IV from that substation. This means the current drawn by the substation is I=P/V and the higher the transmission line voltage, the smaller the current. The line loss is given by Ploss=I²R, or, substituting for I,

Ploss = P²R/V²

Since P is fixed by community demand, and R is as small as you can make it (using big fat copper cable, for example), line loss decreases strongly with increasing voltage. The reason is simply that you want the smallest amount of current that you can use to deliver the power P. Another important note: the loss fraction

Ploss/P = PR/V²

increases with increasing load P: power transmission is less efficient at times of higher demand. Again, this is because power is proportional to current but line loss is proportional to current squared. Line loss can be quite large over long distances, up to 30% or so. By the way, line loss power goes into heating the transmission line cable which, per meter length, isn't very much heat.

[emphasis is mine]

In my searches, I came across this Wikipedia page on distributed generation:

http://en.wikipedia.org/wiki/Distributed_generation

One favored source is solar panels on the roofs of buildings. The production cost is $0.99 to 2.00/W (2007) plus installation and supporting equipment unless the installation is DIY bringing the cost to $6.50 to 7.50 (2007).[1] This is comparable to coal power plant costs of $0.582 to 0.906/W (1979),[2][3] adjusting for inflation. Nuclear power is higher at $2.2 to $6.00/W (2007).[4] Most solar cells also have waste disposal issues, since solar cells often contain heavy-metal electronic wastes, (CdTe and CIGS), and need to be recycled. The plus side is that unlike coal and nuclear, there are no fuel costs, pollution, mining safety or operating safety issues. Solar also has a low duty cycle, producing peak power at local noon each day. Average duty cycle is typically 20%.

Another favored source is small wind turbines. These have low maintenance, and low pollution. Construction costs are higher ($0.80/W, 2007) per watt than large power plants, except in very windy areas. Wind towers and generators have substantial insurable liabilities caused by high winds, but good operating safety. Wind also tends to be complementary to solar; on days there is no sun there tends to be wind and vice versa. Many distributed generation sites combine wind power and solar power such as Slippery Rock University, which can be monitored online.