The first solar panel that was ever installed had an efficiency rate of 1%. Back in 1883, New York inventor Charles Fritts created the first solar panel. The efficiency was very low, and the price very high, so the technology was put away until the mid-20th century. In the 20th century, the. To better understand how big of a solar panel system you need in your household, you should pay attention to the kW and kWh. What is the. Now that we understand what kW and kWh mean, it is time to have a look at the price per Watt and price per kilowatt. A kilowatt is simply 1000 Watts. Likewise, a kilowatt-hour is simply 1000 watt-hour (therefore: kilo-watt-hour). When we speak of entire solar panel. As the total cost of going solar in the USA has been on the decline in the past decade, the federal tax credit was introduced to bring the average total cost even further down. Once we know the power of our system, we can deal with the production. Your solar system will keep producing electricity whenever there is sun and over its lifespan, your residential system will produce a certain amount of electricity. Solar energy cost per.