Power Generation Balancing Values :

Today, I totaled up the relative costs of all available power generators on this server, for now.  I then factored in the difficulty to set the generator up, the danger to your base in having such a generator, the amount of maintenance needed after setup, and whether the resource the generator uses is renewable (aka infinite) or not.  I found that surface area taken up is not much of a factor, because each square you add per generator needs 6 blocks of shielding to protect it from griefers.  The energy shield to cover those squares is less expensive than the power output of the worst generator that eats area.

Here's what you need to know : the actual EU output per tick over a full Minecraft day.

1.  Solar Panel : 0.5 EU per tick with no weather, about 0.4 EU/tick factoring in rain.
2.  Wind Generator : with perfect setup at top of map, 2.88 EU/tick.  Note that turbine blades can break during a windstorm, but output increases.
3.  Water Mill : in passive mode, 0.25 EU/tick when completely surrounded by water.  If fed buckets by hand or automatically, 1 EU/tick.
4.  Geothermal Generator : both Mark I and Mark II output 16 EU/tick, and produce 16,000 EU from 1 lava bucket.
5.  Buildcraft Combustion Engine + Energy Link : each combustion engine produces 15 EU/tick.  Note that the engines can explode and destroy a significant area, and that there are bugs that can cause them to explode.  Also, they have bugs caused by the mod buildcraft.
6.  Nuclear Generator : Output varies.  It is 80% of the values shown on the reactor calculator at this calculator .

The example reactor there will produce 678 EU/tick.  Note that nuclear fuel lasts for 5 times longer duration on this server, so the example reactor will breed as much fuel as it uses at the end of 1 full cycle.  The ice blocks make it semi safe.  Note it will require 4160 stacks of ice over that cycle.  Also note that the explosion of a single failed reactor can destroy several chunks and will cut through many layers of reinforced stone.