Here’s an interesting “believe-it-or-not” fact. Find a great location for a 400-watt solar panel in the Valley of the Sun. Have it produce electricity over a life of 30 years. The total power equals what a 3000 sqft home uses in one year – 20,000 kWh!
At an installed cost, after tax credits, of $2/watt the solar electricity would be generated at 4 cents/kWh as compared to current average utility rates of 12 cents/ kWh, or 3 times more. Hence the tagline “Invest $1 today, save $3 tomorrow!”
Will all panels produce 20,000 kWh of electricity over their lifetime? The correct answer: Some more and some less. But why?
The full answer comes from a deep dive into the many reasons. Mercifully, we’ll only wade into the shallow end.
First off is the weather, and in particular, sunlight – how long does it shine, and at what intensity? Temperature – panel performance is reduced as the air heats up. Clouds and snow also have a negative effect.
Next is the direction the solar panel faces, its tilt, any shading, and cleanliness.
Then panel specs of wattage, degradation, and temperature coefficient. Nice to be told “you’re aging well”, and not “you’re degrading well”. Better leave that term for solar panels. I digress.
Finally, the number of years a panel stays in service is equally important. Fortunately, solar electric systems can be warrantied and production guaranteed for 30 years.
This highlights at least a dozen different influences on how much power a solar panel will produce over its life. Fortunately, the future weather is broadly predictable and a solar power system can be well designed for a specific property.
The end result, is a good estimate of what you could expect solar panels to produce over their life on your property. And all without the deep dive!