According to research, "Solar cell efficiency refers to the portion of energy in the form of sunlight that can be converted via photovoltaics into electricity by the solar cell.cell efficiencies The efficiency of the solar cells used in a photovoltaic system, in combination with latitude and climate, determines the annual energy output of the system. For example, a solar panel with 20% efficiency and an area of 1 m2 will produce 200 kWh/yr at Standard Test Conditions if exposed to the Standard Test Condition solar irradiance value of 1000 W/m2 for 2.74 hours a day. Usually solar panels are exposed to sunlight for longer than this in a given day, but the solar irradiance is less than 1000 W/m2 for most of the day. A solar panel can produce more when the sun is high in the sky and will produce less in cloudy conditions or when the sun is low in the sky. The sun is lower in the sky in the winter. In a high yield solar area like central Colorado, which receives annual insolation of 2000 kWh/m2/year".

Taking all these efficiencies of different solar cells into consideration - the average home owner does not have access to the higher efficiency solar panels. These typical home solar photovoltaic panels have an average rating is between 15% - 18% efficiency. In the above "grid charging" reference of a Tesla Model 3 battery at 100 kWh -  we examine the amount of solar that is required to charge up the battery to 100%. The typical residential rooftop solar array is 6 KW producing 720 kWhs to 900 kWhs per month.

This chart is a typical example of grid connect rapid charging times for the Tesla model 3 at home, work or public charging stations. For home charging there are three Charging time for a Tesla Model 3different types of charging connections that allow for direct connect from 120 or 240 volt and the Tesla Charging unit itself: NEMA 5-15 charging, NEMA 14-50 charging to a Tesla Wall Connector charging. Each system has its own rate of charging for home units.

With a NEMA 5-15 system it can take it can take anywhere from four to eight days to charge your empty Tesla battery to 100% using a standard home electrical configuration of 110 Volt - 15 amp. Next up is the NEMA 14-50 charger. This system allows for other plug configurations and higher current wall plug in: 220 Volt - 50 Amp - that can be a dedicated line just for charging. This charging system will offer 30 miles for every hour of charging. To go from 0% to 100% will require between 9 and 22 hours of charging time. Last on the list is the Tesla Wall Connector.  These are the fastest systems for charging your Tesla at home. Using a Tesla Wall Connector you'll get 44 miles of range per hour of charging. It will take anywhere from 6 to 15 hours to charge a Tesla battery from empty to 100%.

Being that the average American’s commute is only 30 miles round trip (37 round trip in California and 66 round trip in NY and 62 in NJ), recharging your Tesla Model 3 after a long day of work will take 10 hours using a NEMA 5-15 charger, one hour to recharge using a NEMA 14-50 charger, and only about 40 minutes using a Wall Connector. Considering California the increase in charging time is only 20% but in NJ and NY - that at home charging time can double the time rates mentioned above.

Now let's bring in residential roof top solar as the primary energy source for charging the Tesla Model 3 while using the same connections mentioned above. This requires another Solar panels on hometime breakdown. The typical residential roof top solar array is 6 KW. Depending on which manufacture of recent production each solar panel can be from 250 watts to 400 watts. The average 250 W solar panel can generate around 30-40 kWh of AC power each month.

Let’s make use of the higher number (40 kWh) in our calculations: 250 kWs X 8760/ 1000 X .22 capacity factor/365 = 1.32 kWhs per day X 30 days in a month = 39.6 kWhs. Given that single, low output solar panel produces roughly 1.32 kWh per day of electrical power and a Tesla Model 3 has a 100 kWh battery this indicates that you need to install as many as 76 solar panels (100 kWhs / 1.32 kWhs per panel = 75.75 total panels) to generate electricity to power your Tesla Model S each day – assuming that you start the charging process with a battery totally drained of electricity.

To consider the average mileage driven and charging capacities of solar - without using the solar array for home electronics - it would take a typical 6 kW solar array 2 hours each day to charge the Tesla 3 100 KW battery just enough to commute back and forth to work 30 miles round trip. If we look at a realistic commute back east of 60 miles round trip - it would require a 4 hour long charge per day using a 6 KW solar array. Since the average capacity factor is 5.35 hours per day - there would be no power generated by the solar the roof top solar array to use for home energy consumption. If you only wanted to charge a Tesla Model 3 at home for daily commute and use external super charging for long distances then a 12 KW roof top system would suffice power up the home and charging a Tesla Model 3. As of July 2021, the average cost of solar in the U.S. is $2.76 per watt ($33,120 for a 12 kilowatt system). That means that the total cost for a 12kW solar system would be $24,509 after the 26% federal solar tax credit discount (not factoring in any additional state rebates or incentives).