  Synchronisation algorithms are central to collaborative editing software. As
collaboration is increasingly mediated by mobile devices, the energy efficiency
for such algorithms is interest to a wide community of application developers.
In this paper we explore the differential synchronisation (diffsync) algorithm
with respect to energy consumption on mobile devices. Discussions within this
paper are based on real usage data of PDF annotations via the Mendeley iOS app,
which requires realtime synchronisation.
  We identify three areas for optimising diffsync: a.) Empty cycles in which no
changes need to be processed b.) tail energy by adapting cycle intervals and
c.) computational complexity. Following these considerations, we propose a
push-based diffsync strategy in which synchronisation cycles are triggered when
a device connects to the network or when a device is notified of changes.
