If your electrical bill is higher than it should be, more than one possible cause may be in play, and diagnostics can get confusing. There could be a malfunction in an appliance, or power could be flowing to ground through a bad connection. Your home also may have numerous phantom loads, power usage from electronics and other devices that continuously draw power even when they appear to be off. You can pinpoint major leaks by flipping breakers, but finding phantom loads calls for a different procedure using a device that measures power use at individual receptacles.
Turn off the main breaker at your home's service panel (breaker box) and look at the electric meter. The meter should not be running -- if it is, you have discovered the leak. It is somewhere between the power leads and the panel, and you need to have it fixed immediately. Call an electrician.
Flip off all the breakers in the panel and turn on the main breaker. Go through the house, turn off all the light switches and unplug everything that's plugged in, including all the major appliances. Some appliances, such as the stove and water heater, may be hardwired, so you can't unplug them. Turn those appliances off or set them to their lowest settings.
Check the meter again; it should be motionless. Turn on each breaker, one at a time, and check the meter each time you do. If it remains motionless, turn off that breaker and try the next one.
Double-check the circuit if the meter starts to turn when you turn on a breaker. You should be able to get an idea of which lights, receptacles or devices it controls by looking at the label on the panel door. If you're sure everything is unplugged, and all switches are off, there is an open connection in the circuit, possibly caused by degraded wire insulation. This is a dangerous condition; you should call an electrician.
Watch the meter when you turn on the breaker controlling a hardwired appliance. If it begins moving, note whether the appliance has cycled on. If it hasn't, it may have an internal fault; for example, an electric water heater may have a corroded heater element. Have that appliance serviced.
Turn all the breakers back on, leave the lights off and make sure the meter isn't running, then plug in your appliances one by one. All the appliances should be off. Any one of them that causes the meter to start turning needs to be serviced.
Test each appliance for phantom power loss by using a power monitoring meter. Plug the meter into the receptacle, then plug the appliance into the meter. Leave the appliance off for two or three days, then check the meter. A positive reading indicates power loss.