Pen recorders:

A meter movement is equipped with a marking device, generally a pen, to keep a graphic record of the level of some quantity with respect to time. Such a device is known as pen recorder. The paper, with the calibrated scale, is taped to a rotating drum. The drum, driven by a clock motor, turns at a slow rate, like 1 revolution per hour or 1 revolution in 24 hours. A simplified drawing of pen recorder is shown in the figure given below

Figure--   Simplified drawing of a pen recorder.

A device of this type, along with a wattmeter, can be used to get a reading of power consumed by your household at times during the day. In this way you might tell when you use the most power, and at what times you might be using larger power.