The XENON1T experiment is leading the sensitivity to spin-independent, elastic WIMP-nucleon scatters, excluding cross-sections down to 7.7·10−47 ^{−47} cm2 ^2 at a mass of 35 GeV/c2 ^2 (90% CL) with the first science run of 34 days. A second science run with 247 live days is currently under analysis. The XENON1T data is also scrutinised for other rare-event searches, including the neutrinoless double beta decay of 136 ^{136} Xe. Here we optimise the search for a peak at the Q-value of 2.45 MeV, which is in a much higher energy region than the standard WIMP analysis. We also show the discovery potential of the future XENONnT and DARWIN projects, which will be competitive to dedicated double beta decay experiments.