A 3 m(3) fixed dome Janata biogas plans installed in the hilly conditions of Himachal Pradesh was evaluated for its gas production efficiency for nearly 10 years. The monthly variation in the mean ambient temperature affected its digester temperature and hence, rate of gas production. The average rate of daily gas production from the plant with daily feed rate of 20 kg cattle dung/m(3) rated capacity of the plans consistently decreased year after year: This decrease in the rate of daily gas production for the quarter representing the peak summer months was more compared to the rate for the quarter representing winter months. The decrease in gas production was due to lumps of digested slurry formed in the digester To maintain consistent higher rate of gas production the plant needs cleaning every fifth year.