Scalable grid scales in meter display

The meter display should have grid lines on it that are scalable and can be turned on and off by the user that reflect the wattage. Currently there is a number at the top that shows the maximum wattage for the current scaling but there should also be a series of horizontal grid lines at reasonable intervals for the scaled display that show the wattage values. This grid should be optionally turned on and off by the user and the on and off selection should be retained between uses of the app.