We have a white meter also known as 'tariff noche'. Basically, its like Economy 7 in UK where between hours of 11pm and midday we pay approx 5 c per unit and after noon it is approx 20 cents per unit. The normal meter charges 15 cents per unit 24 hours a day...I would need to check the exact times the cheap rate is applicable.
White meter is great if you live here or don't rent your place out. I cook my meat, heat my water and do my washing in the morning. I am very careful....I don't have aircon but if I did again I would only use it in the cheaper hours.
My last bill was 122 Euro ..that included approx 4 hours water heating per day and washing machine on probably 5 mornings out of 7.
I hope this helps!