With a bad power factor, the current in the wires is going to be higher, which requires thicker wires, bigger transformers, bigger generators and produces more loss.
That's why power factor correction is necessary, and companies get charged extra if they don’t do it properly. It’s about compensating for the additional cost on the grid for reactive power.
In this specific case, the smoke alarm is a capacitive load.
Most machines an appliances will be inductive loads.
They are usually not compensated completely, so in reality, the capacitive load of the smoke alarm won't cause additional current on the wires to the power plant.
Because of this, only the active power should be used for calculating the energy consumption (which is still horribly high).