From what I've read, the Tokamak was able to provide sufficen power for approx. 5000 houses during the experiment using the mixtures required for commercially applicable fusion (namely 50/50 deuterium/tritium, IIRC). Didn't say whether it actually produced enough to sustain the reaction or not, but from what my professor explained, essentially, you need power to start the reaction, and for the magnetic bottle preventing a detonation that would make anyone regreat losing containment (aka, a nuclear device).