There are two different statements, which seem to be contradictory, but are simply saying different things:
- ITER aims to produce 10 times as much heat energy as put in
- ITER will consume more total energy than it generates
The confusion comes from a simple misunderstanding: heat energy is not the only input - for instance, power is needed to cool superconductors; nor is the heat energy a directly usable output - to produce electricity, it would be used to produce steam and turn a turbine. As a research device, ITER is neither designed to capture the energy produced, nor to minimise the total energy used to create the plasma.
As a very rough analogy, picture an internal combustion engine which requires energy to run fuel pumps, starter motor, etc; and which will eventually produce useful energy via a drive train and a dynamo. In a prototype, you can ignore the efficiency of those "external" components, and study how well the engine extracts energy from the fuel. Current fusion reactors are like an engine where the fuel ignites only while the starter motor is running, because it doesn't turn the engine fast enough to sustain the process; ITER's aim is the equivalent of using the fuel to turn the engine faster than the starter motor, but with no drive train attached.
The Wikipedia article (permalink from the time this question was posted) summarises the aim thus:
to achieve enough fusion to produce 10 times as much thermal output power as thermal power absorbed by the plasma for short time periods
And goes on to say:
ITER's thermonuclear fusion reactor will use over 300MW of electrical power to cause the plasma to absorb 50 MW of thermal power, creating 500 MW of heat from fusion for periods of 400 to 600 seconds. This would mean a ten-fold gain of plasma heating power or, as measured by heating input to thermal output, Q ≥ 10. The European STOA Fusion Project cautions that this figure refers only to the energy of the plasma itself, and that practical capture of this energy for electricity production would introduce significant inefficiencies which ITER is not designed to overcome.
The ITER website confirms this in an FAQ "What is the difference between plasma energy breakeven and engineering breakeven?":
Plasma energy breakeven is the moment when the efficiency of the fusion reaction reaches Q = 1 (...); that is, when the total fusion power produced during a plasma pulse equals the power injected into the systems that heat the plasma.
[...]
Engineering breakeven would take into consideration all of the plants systems—and not just external heating systems—in the evaluation of the input/output power balance of an electricity-producing fusion power plant. Commercial fusion plants will be designed based on a power balance that accounts for the entire facility [...]
The significance of the Q=10 target is not that it makes the design a useful source of power in itself, but that it allows study of "burning plasma":
When heating by the helium nuclei ("alpha heating") is dominant (over 50 percent) the plasma is said to be a "burning plasma."
The net energy gain is in the plasma, allowing the reaction to be somewhat self-sustaining. That gives the reactor properties that haven't been achieved before, and allows study into how future devices could operate.
