Solar panels over rice boost farmers’ revenue fivefold, but crops worsen
The rice paddy used in a science experiment by a University of Tokyo team. Solar panels can be seen above the rice plants
If farmers install solar panels over their rice fields, their overall revenue, including income from selling solar-generated electricity, can improve more than fivefold, a recent Japanese study has shown.
However, the team led by University of Tokyo agricultural science professor Yoichiro Kato also found that this solar power generation-farming method reduces rice yields by roughly 20% and worsens qualities including flavor, among other issues.
“Solar sharing,” the practice of generating solar power on farmland, is hoped to promote the use of renewable energy while also enabling boosted food production to support a growing global population.
As such, it will be necessary to develop cultivation and management technology that can minimize yield reductions and stabilize crop quality.
The team’s findings were published in late March in the online edition of an agricultural science journal by Elsevier, a major academic publisher based in the Netherlands.
The team of scientists conducted experiments over six years starting in 2018, with the cooperation of a farm in Ibaraki Prefecture.
They compared the yields and total revenues, including income from electricity sales, between a rice paddy where 27% of the area was covered with solar panels and a regular one.
In the solar panel-covered paddy, the amount of sunlight over the course of a year was reduced by 21-30% compared to the conventional paddy, and the average maximum temperature was 0.8 degrees Celsius lower. These factors hindered rice growth, resulting in a 23% decrease in average yield.
Meanwhile, solar power generation remained stable each year regardless of weather conditions.
Although the purchase price under Japan’s fixed-price feed-in tariff system for renewable energy has been falling every year, the team calculated that, using the 2025 pricing, the income from the solar sharing setup was five times greater than from rice farming alone.
However, challenges remain. The appearance of the rice deteriorated, with the endosperm turning whitish and cloudy.
Furthermore, levels of amylose and protein increased, resulting in poorer taste. The study highlights the need for the development of rice varieties and cultivation techniques suited for solar sharing.
Kato stated, “The decline in rice quality lowers its grade by about one level, but even considering that, solar sharing still results in greater profitability.”
Regarding future prospects, he added, “We aim to first establish this technology in Japanese rice paddies to help farmers increase their profits, and then expand it overseas including in other Asian countries.”
