The usage of the phone's CPU is usually around 1w, but could jump to 5-6w when boosting to solve a nasty challenge. At 20s per challenge, that's 0.03 watt hours. You need to see a thousand of these challenges to use up 0.03 kwh

My last power bill was around 300 kwh or 10,000 more than what your phone would use on those thousand challenges. Or a million times more than what this 20s challenge would use.