What factors make my bill vary each month?

Even if your habits don't change, your bill can vary due to external factors:

1. The market: on the Tarifa Transparente, the energy price goes up and down every hour.
2. The billing calendar: billing cycles are not calendar months — they can be 28 or 34 days, which affects the total.
3. Time slots: if in a given month you use more electricity during Peak hours (expensive) than Off-peak (cheap), your average price will go up.
4. Meter readings: if your distributor sends an estimated rather than an actual reading, there may be a subsequent adjustment.