Mae'r adroddiad BRE yn awgrymu bod y cwymp o ganlyniad i gyfuniad o gynnydd mewn incwm cartrefi, defnyddio llai o ynni yn y cartref o ganlyniad i welliannau o ran effeithlonrwydd ynni, a phrisiau nwy ac olew is.
The BRE report suggests the decrease is due to a combination of rising household incomes, a reduction in household energy consumption due to energy efficiency improvements, and decreasing gas and oil prices.