A data providing method is carried out by a computer (460) built in a data processing system (1) which is designed to collect log information from electronic devices through a network (30) and provide services based on that log information for authenticated users. The data providing method includes: receiving an air conditioner (102a, 102b)'s log information through the network; generating display data by reference to pieces of information which are included in the air conditioner's log information and which indicate (i) a preset temperature of the air conditioner, (ii) an outdoor temperature outside a living space in which the air conditioner is installed, and (iii) an indoor temperature of the living space in which the air conditioner is installed, the display data representing a trend of change of a turnaround time that indicates how long it takes from when the air conditioner starts operating until the indoor temperature reaches the preset temperature; and providing the display data for an authenticated user's display terminal (130a, 130b).