PV Gap

Jennifer Said:

How much energy do solar panels produce in Kwh?

We Answered:

Hey Kyle, the short answer is about 80 watts in direct sun. Most solar panels today operate at around 12 - 14 % efficiency, meaning they convert about 1/8 of the suns energy to electricity, the rest just heats up the panel. That might sound terrible, but consider many of our current day technologies. A car is about 25% efficient, an incandescent light bulb about 4%. A common panel today, at 12% efficiency will produce about 10 watts per square foot, so the panel in your example at 2' x 4' = 8 sq feet, should produce about 80 watts. In terms of kwh, if you have 4 hours of sun per day, 80 watts would equate to about 1/3 kwh per sunny day.

In most cases, solar panel efficiency is not a concern. A good example of this is our home. We produce about 80% of our own electricity using a solar array and a small wind turbine. The array is 1.4 kw, or 1,400 watts peak power. There are 12 panels, each is about 2 feet wide and 5 feet long, and rated at 120 watts. That entire array fits very nicely on the roof of our single car carport, with some room to spare. If the panels were 25% efficient instead of 12, they would take up half the space, and cost about 20% more money. This would accomplish nothing more than expose more of our garage roof to the sun, and reduce the size of our bank account.

Some new companies are touting their solar panels as being the most efficient. One company claims to have reached 18% efficiency. That's great, but for most users, it's of no concern, because the space on the roof of their home is way more than they need for even the most inefficient panels today, and generally they cost less per unit power in the first place. All of this applies to solar electric panels, or photovoltiacs. In the case of thermal panels, the ones that heat water or air, they run much higher, in the 50 - 60 % range, but it is a little hard to quantify because they are also affected by ambient temperatures more dramatically. If you're interested in learning more, check out some websites below. Take care, Rudydoo