Pak irfan memasang 2 lampu 25w/220v, 2 lampu 40w/220v, 1 buah lampu 60w/220v, dan 1 buah lampu 10w/220v dirumahnya. seluruh lampu rata rata dinyalakan 8 jam set

P1 = 2 × 25W = 50W
P2 = 2 × 40W = 80W
P3 = 1 × 60W = 60W
P4 = 1 × 10W = 10W

Perhitungan energi listrik
W1 = P1 × t = 50 × 8 = 400 Wh
W2 = P2 × t = 80 × 8 = 640 Wh
W3 = P3 × t = 60 × 8 = 480 Wh
W4 = P4 × t = 10 × 8 = 80 Wh
———————————————— +
Jumlah = 1600Wh
W 1 hari = 1,6kWh
W 30 hari = 1.6kWh × 30 = 48kWh

Biaya per 30 hari = W 30 hari × harga per kWh
= 48 × 750
= Rp36.000,-


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