固定価格買い取り制度(FIT)における太陽光発電の機動的な買い取り価格改定の必要性

摘要

2012年7月，「電気事業者による再生可能エネルギー電気の調達に関する特別措置法」(以下FIT法)に基づく固定価格買取制度(Feed-in Tariff,FIT)が開始した.経済産業省は調達価格等算定委員会が公表した買い取り価格の意見を完全探用し，買い取り区分と価格を決定した.買い取り価格については多方面から大きな関心が寄せられ，決定に至るまで活発な議論がなされていた. 制度開始前に買い取り価格に関心が集中するのは当然であるが，FITについては電力料金に上乗せして回収するか否か，買い取る量は全量か余剰か，また価格改定の頻度など様々な論点がある.特に太陽光発電は計画から発電•稼働までの期間(リードタイム)が短く，制度設計の仕方によっては過度な導入ラッシュが起きる可能性がある.%With the introduction of the feed-in tar iff(FIT) system in July 2012, there is a growing interest in expanding photovoltaic(PV) install at ions. The history of Germany and other countries, however, shows that a failure to adjust FIT prices promptly could result in a rush in installation, resulting in a huge policy cost. In particular, commercial rooftop PV systems are unique for their short lead time(about a couple of months) and a possible rapid decline in prices. Here, we develop a simple model of the PV installation as a function of cost decline scenarios and FIT prices, and examine the effect of the time period for which the FIT price is updated. The more frequent the adjustment of FIT price is, the smaller the policy cost of unit installation. The rapid FIT adjustment can also reduce the uncertainty of the policy costs and PV install at ions. The law in the present form presumes updating every year, or every six months in a special circumstance, although adjusting every one or two months is recommended. It does not explicitly recognize the category of commercial rooftop systems, either. A more adaptive policy framework is preferable, with frequent price adjustments and extensive price monitoring.