Why doesn't the total shown on my Digital Display match the total shown on my electricity bill?

It is unlikely that the Power Monitor will exactly match your bill.This product is intended to help you understand the cost of power as you use it, and to estimate your effectiveness as you learn to be more efficient in your energy use. Some sources of error include: Not having the current rate programmed into the Display.For example, some utilities charge different rates in winter and summer.Some utilities change their rates every month. Not including taxes and fees when you calculate the rates to enter into the display. For example, fixed fees and surcharges cannotbe programmed into the display. Not knowing the exact time and date when the billing period starts, so you can reset the accumulated total. For more information on Black & Decker's line of energy saving prodcuts. Please Click Here