Many window cleaners count panes generally the same. There are slight variations, though. The following will guide you though the basic process.
A window usually doesn’t equal a pane. We count each pane of glass. If you have a sliding window, then you have at least two panes, sometimes three or more. A sliding glass door is two panes. One pane slides, and the other doesn’t. The house in this example has 8 panes that you can see.
Some windows are just one pane. They are usually called picture windows, and do not open, although some do crank open or push open. Just remember that if a window is separated by a frame, it counts as more than one. Also if it is an unusually large pane, then we will count it as two (or possibly more).
There are two major types of panes. The first is a regular pane. A regular panes is one that can be reached on the inside without a ladder. The panes in the example picture from above, were regular panes. The 2nd-story windows are bedrooms, and you can walk right up to the windows on the inside.
There is another type of pane called a “french pane”. Some window cleaners call them truly-divided-light, or TDL. They are often on interior doors (like to a den). They are also often on exterior doors to a patio or balcony. French panes are counted in their own category, because we charge less per pane to clean them. Click here for some examples of french panes. If you have a large house, and most of the windows are french panes, then we might want to come out to do the estimate on-site.
Be careful not to count removable grids (mullions or inserts) as french panes. They are just removed and then the glass is cleaned like a normal pane. We do charge to take down and replace the grids, because it does take time, and sometimes they refuse to go back in correctly. Customers can undertake this job before we arrive to avoid this charge (generally $1-2 per grid).
The last common pane is a skylight. These are pretty straight forward. Sometimes we give the customer a break if there is a bay of them, and they are small. Then we would call them skypanes, and count them up separately. Skypanes can be cheaper than skylights. It all depends on their size and accessibility.
If the grids are attached to the outside of the glass permanently, but absent on the inside, then we would probably want to come out and do an on-site estimate.