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.
If you live in the South and already own solar panels, it could take you just under three years to make up the cost of the $3,000 Tesla Powerwall battery. But if you live in the Pacific Northwest and don't have solar panels, it could take you at least 16 years to make up the cost of buying Tesla's new home battery.