Evaluation of Photovoltaic Power Generation Systems in Residential Homes in Japan: A Partnership Program of Utility and Consumers’ Cooperative

Takahiro Tsurusaki, Akio Tanaka, and Hidetoshi Nakagami, Jyukankyo Research Institute

Keywords

Abstract

A subsidy program for introducing photovoltaic (PV) power generation system to residential homes in Japan was launched by the Japanese government in 1994, with total capacity of the installed systems reaching 64.6 MWp in 1998. The cost of installation has been reduced to about $9,000! kWp in 1999.

From 1997 to 1998, apart from the government program, the private-sector Seikatsu Club Consumers’ Cooperative and the Tokyo Electric Power Company (TEPCO) granted average $4,500/kWp to home owners who were planning to install PV systems in the Tokyo area. Out of 376 applicants, 132 households were selected through careful consideration, and grid-connected systems (total 412 kWp, mean 3.1 kWp) were installed on the rooftops of their houses.

According to measurement results from October 1998 to September 1999, the average PV electric output was 2,784 kWh/year (887 kWh/kWp/year), equivalent to 45% of monitored household electricity consumption. The average savings per household was $641/year. Therefore the cost of installation is to be paid back in 42 years of savings. With consideration of subsidy, it is to be paid back in 23 years.

The electric output of PV system was 34% of total capacity during the TEPCO peak demand period. And electricity consumption for cooling was reduced 26% compared that of before installation. This might be brought by reduction in cooling load by PV arrays blocking roof sunlight and controlled air conditioner by monitored households.

From the result of measurement and estimated potential installation capacity mentioned on existing studies, the potential electricity generation by PV system in Japan would be 25.8 TWh/year, equivalent to 14% of the total residential electricity consumption in 1998.