  We examine 12 studies on the efficacy of disaggregated energy feedback. The
average electricity reduction across these studies is 4.5%. However, 4.5% may
be a positively-biased estimate of the savings achievable across the entire
population because all 12 studies are likely to be prone to opt-in bias hence
none test the effect of disaggregated feedback on the general population.
Disaggregation may not be required to achieve these savings: Aggregate feedback
alone drives 3% reductions; and the 4 studies which directly compared aggregate
feedback against disaggregated feedback found that aggregate feedback is at
least as effective as disaggregated feedback, possibly because web apps are
viewed less often than in-home-displays (in the short-term, at least) and
because some users do not trust fine-grained disaggregation (although this may
be an issue with the specific user interface studied). Disaggregated
electricity feedback may help a motivated sub-group of the population to save
more energy but fine-grained disaggregation may not be necessary to achieve
these energy savings. Disaggregation has many uses beyond those discussed in
this paper but, on the specific question of promoting energy reduction in the
general population, there is no robust evidence that current forms of
disaggregated energy feedback are more effective than aggregate energy
feedback. The effectiveness of disaggregated feedback may increase if the
general population become more energy-conscious (e.g. if energy prices rise or
concern about climate change deepens); or if users' trust in fine-grained
disaggregation improves; or if innovative new approaches or alternative
disaggregation strategies (e.g. disaggregating by behaviour rather than by
appliance) out-perform existing feedback. We also discuss opportunities for new
research into the effectiveness of disaggregated feedback.
