Agreed, a jump drive only needs energy, but wast amounts. In a fusion economy it needs both a bit of energy and a lot of fuel (to be turned into energy).

Only antimatter power or other exotic power systems can provide the needed energy without large amounts of fuel.

Let's estimate:

Take a 1000 Dton ship with J-1 at TL-12. It needs a 20 Dt power plant producing 300 Power to power basic systems (200 Power) and either the M-drive or the J-drive (100 Power). It uses 2 Dt fuel over 4 weeks, or 1 Dt per two weeks.

In two weeks the PP would produce 300 Power for 2 × 7 × 24 × 10 = 3360 turns or about 1 000 000 PowerTurns = 1 MPowerTurn from 1 Dt fuel.

A J-1 would require 100 Dton fuel or about 100 MPowerTurn energy.

One Dt of HiEfficiency Batteries holds enough energy to produce 60 Power for 1 turn so 60 × 1 = 60 PowerTurns/Dt.

100 MPowerTurns required / 60 PowerTurns/Dt ≈ 1.7 million Dt batteries required.

So roughly a 1 000 Dt ship would require 1 000 000 Dt batteries to power a jump-1. Obviously that is not happening...

Estimate Two:

At very roughly 1 Power = 10 MW, 100 MPowerTurn (one jump) would be 100 000 000 PowerTurn × 10 [MW/PowerTurn] / 10 [turns/hour] = 100 000 000 MWh = 100 TWh = 100 billion kWh.

That is roughly what ten nuclear reactors of 1000 MWe each produces in a year. Or twenty Hoover dams. Or about 100 large wind power parks with a total of tens of thousands wind mills covering 7800 km² (≈Delaware) (Shepherds Flat Wind Farm).

For one jump...