Since the Great East Japan Earthquake in 2011, development and utilization of Demand Response (DR) has been getting more active in Japan, which can, as one of the demand control methods, contribute to efficient power supply. Necessity of such DR has also been pointed out recently that does not put a burden on consumers. Peak Time Rebate (PTR) type DR does not impose too much a burden on consumers. However, little is known so far about its effectiveness. The authors have designed a PTR type DR program, implemented it in a demonstrative field test targeting ordinary home consumers and observed their electric power use reduction in the peak time since 2014. In this study, based on the field test results, we analyze the changes in electric power consumption during the DR event time. Moreover, influential factors on the reduction of electric power use are hypothesized and tested against the observed data using a stepwise multiple regression analysis technique, which clarifies features of the consumers who have high potential for reduction of electric power consumption through the PTR type DR program. The ongoing deregulation of electric power industry in Japan is promoting new methods for power system control and energy management. The findings described in the paper will be very useful for controlling the power demand effectively using DR programs.