Lets see, fusion is first available at TL 8, and has a minimum size of 50 cubic meters at that TL. a 50 cubic meter fusion plant has a power output of 1000 (20 per cubic meter), weights 10,000kg, requires 50 liters of fuel per hour, and costs 500,000 credits.
A turbine of equivalent size and TL puts out 26 power per cubic meter, but because of the power efficiencies on the next page, actually puts out 1.5 times that. So 39 power per cubic meter (almost twice the fusion plant), for a total power output of 1950. It only weighs 4,500kg, and costs 212,500 credits. The only drawback is that it does require 900 liters of fuel per hour.
Lets make the turbine have the same power output as the fusion plant. It needs a total power output of 1000, so a 26 cubic meter plant would do. That drops the weight down to 2,340kg, the cost goes down to 110,500 credits, and now only requires 468 liters of fuel per hour.
Hydrogen fuel cells are also more power efficient. A 50 cubic meter fuel cell puts out 27 power per cubic meter (total of 1350), weighs 7,500kg, requires 100 liters of fuel per hour, and costs only 90,000 credits.
Of course, all those are big plants. Lets look at something smaller, say 1 cubic meter. We'll have to advance to TL 12 to get a fusion plant that small. Turbines and fuel cells stop at TL 10.
TL 12 fusion plant: 24 power, 150 kg, 1 liter fuel per hour, 15,000 credits.
TL 10 turbine: 30 power, 125kg, 8 liters fuel per hour, 5,000 credits.
TL 10 fuel cell: 22 power, 125 kg, 1 liter fuel per hour, 2,400 credits.
All powerplants can also be made fuel efficient (half the fuel per hour, double the cost of the plant) or improved fuel efficient (one quarter the fuel, 4 times the cost). An Improved Fuel Efficient TL 10 Fuel Cell of 1 cubic meter only requires 0.25 liters of fuel per hour, and costs 9,600 credits.
If you do some conversion, you can see that you can power a starship with Improved Fuel Efficient fuel cells better then you can a fusion plant. They would be half the price, and require only 2/3rds the fuel. Drawback is a 2% loss in power, which is easily made up when you but in a slightly bigger fuel cell. (Easily done with the cost savings, and the tonnage savings from less fuel required.) Makes you wonder why all of those Imperial starships mount TL 15 fusion plants, when technology from 5 TLs earlier performs better for cheaper.
I just like making interesting vehicles...
Roll on February 
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