If a geyser is rated $240\,\mathrm{W}-220\,\mathrm{V}$, it means that if the geyser is operated on a $220\,\mathrm{V}$ supply, the electric power consumed by it is $240\,\mathrm{W}$ (i.e. $240\,\mathrm{J}$ of electrical energy is consumed by the geyser in 1s).