The best-known of these tools is probably the hand-held window squeegee, used to remove the cleaning fluid or water from a glass surface. A soapy solution acts as a lubricant and breaks up the dirt, then the squeegee is used to draw the now water-borne dirt off the glass leaving a perfectly clean surface.
Another way of estimating the cost of electricity would be the cost of an ordinary solar system, or $21,000 as shown in the example above. So the cost of a Tesla retrofit system would be in the range of $33,000 to $37,500.
Elon Musk with one of the solar-roof shingles.Tesla. Tesla CEO Elon Musk says the solar roof that will be sold under a combined Tesla-SolarCity will most likely cost less to install than a normal roof. Tesla and SolarCity shareholders voted in favor of the merger, a deal worth $2 billion, on Thursday.