The results really aren’t that surprising, but interesting nonetheless. As summarized nicely by Marginal Revolution:
The authors assigned 691 households in Japan to one of three groups a) a moral suasion group, b) an economic incentive group or c) a control group. The moral suasion group were told that electricity conservation was important and necessary on peak demand days and then over a year when the peak times hit they were sent day-ahead and same-day messages to please reduce electricity consumption at the peak times. The economic incentive group were told that their electricity prices would be higher during certain peak periods and over the year when the peak times hit they were sent day-ahead and same-day messages telling then when the prices would be higher. Prices were approximately 2-4 times higher during the peak times. Control groups had smart meters installed but were not sent messages.
Moral suasion worked but not nearly as well as economic incentives (in the figure, lower use is better).
Read the original paper by Ito, Ido and Tanaka.