The LCLS works by directing terawatts of light in the x-ray spectrum into one place in incredibly fast bursts. The bursts themselves only last femtoseconds, or quadrillionths of a second. With their current operation, the machine can shoot 120 bursts per second. After the upgrade, the LCLS will be able to shoot one million bursts per second, using the same amount of energy. While the bursts are happening more frequently, they're also happening much quicker, reducing the amount of energy spent per burst. That's why one second of bursts on the new kilometer of LCLS will consume the same amount of energy as the older two kilometers, which will both stay functioning. The average energy spent is the same. All in all, the total energy spent in one burst is rivaled by the energy in a hot cup of coffee.