He had to laugh a little at the yearning: Where was a mutant with a truly useful power when you really needed one?

I never really found the power all that useful.

A well-designed motor can convert over 90% of its input energy into useful power for decades.

But most fusion reactions need at least a hundred million degrees before they start to produce useful net power.

Daniel, of course, didn't possess a mind of any useful power.

Ali of this implied that the Singers possessed some possibly useful or dangerous power.

Long underground cables have significant capacitance, which may reduce their ability to provide useful power to loads.

Of the eight built, six produced operationally useful power for an extended period.

This gives the courts a useful power to separate the wheat from the chaff among the pending cases.

The tuning allows the engine to provide more useful low-end power.