How Powerful Are Today’s Solar Panels?

In October, Elon Musk’s SolarCity debuted a new rooftop solar panel that is now the most efficient panel in the world. We wanted to find out just how much power it could generate when installed on an average American home, and compare it to some fun applications of energy.

From your pocket to places around the country (and across the world!), checkout some of these fun uses of energy and how they compare to these new panels.

Please include attribution to SaveOnEnergy.com with this graphic.

Methodology

So, how exactly did we put this graphic together? Where we did get these numbers, and when we had to make our own calculations, how did we do so? Here’s all the details.

Note: The calculations of energy consumption below were computed using the most sensible methodology for the best available data; however, most are best estimates as some cannot be fully measured and energy consumption for anything can fluctuate based off a number of factors.

A single solar panel

The main data point we used in putting together this graphic was the amount of energy a solar panel generates on a yearly basis.

We made the decision that in order to make these numbers seem more realistic, we would calculate the amount of energy that an average American could expect to yield from the best solar panel on the market.

Here are the assumptions we made in this calculation:

  1. The equation. To get all the details on the basic equation used, see this helpful article with explanations for each item involved.
  2. The panel. The exact model of solar panel we used was SolarCity’s new rooftop panel, which was announced in October. Its photovoltaic system has been verified by the Renewable Energy Test Center to have an efficiency of 22.04% (even if this claim was disputed, the previous best was SunPower’s X-Series panel, which had an efficiency of 21.5%, a very close second). The panels range from 1.61 to 1.81m²; going with the concept of the “best”, we went with the largest model (1.81m²).
  3. The environmental conditions. It makes a huge difference between a rooftop in the desert of Arizona & a rooftop in the northwest corner of Oregon. Based off this user-friendly map on page 9 of a consumer guide put forth by the National Renewable Energy Laboratory, we found that a suitable average for the United States would be an annual average solar radiation (with tilted panels) of 1,700 kWh/m².y. Additionally, we calculated this with the assumption of no shading (i.e. trees, other buildings, etc.).
  4. Performance Ratio. Going with the article outlining the equation, we decided that the default value of 0.75 put forth would be a fair mark to use.

As a result, 1.81m² * 22.04% * 1,700 kWh/m².y * 0.75 = 507 kWh/yr

Individual Comparison Points

Now that we had a “unit” that we could compare others numbers to, we dug into publicly available information on various fun uses of energy. Some generated data points we could use out-of-the-box, while others required a bit more math. Here’s how we found each.

  1. 125 smartphones

    There were a number of sources we could’ve used, but found the calculations put forth in this article to be the most accepted (it’s been cited on hundreds of sites, including Scientific American, Gizmodo and Mashable). They came to the conclusion of various models ranging from 3.47kWh/yr (iPhone 5) to 4.49kWh (Galaxy SIII), so we averaged that and came to ~4kWh/yr.

  2. 1 healthy biker on a bicycle generator, non-stop

    This was calculated by the estimates made in this article. The author equated an internet server to require 3,500 kWh/yr, and stated that would be the equivalent to 4 bikers generating a (generous) estimate of 100 watts/hour. Doing the math, 3,500 kWh/yr divided by 4 bikers equates to 875 kWh/yr for each.

  3. An internet server

    This was calculated based off the estimates made in the same article as #2. That number was 3,500 kWh/yr.

  4. An average American home

    This number was pulled right from the source: the U.S. Energy Information Administration. You can find it in this FAQ article. The number given is 10,932 kWh/yr.

  5. To the moon & back in a Tesla Model S

    This number was not easily available. Here are the numbers that were used to come to this calculation:

    • The average distance to the moon is 238,900 miles.
    • The EPA rated its energy efficiency at 237.5 Wh per kilometer, or 38kWh / 100 miles.

    As a result, 238,900 miles = 90,782 kWh. Given that it’s to the moon and back, we doubled that, landing at 181,564 kWh.

  6. A NYC subway car

    This number was also not easily available. It was also tricky to calculate based off the two numbers used for the calculation are not from the same time period. Here’s what we found:

    • A 2004 article from the IEEE stating an annual energy consumption of 1.8 billion kWh.
    • A 2011 article directly from the Metropolitan Transportation Authority of 6,282 active subway cars.

    It’s a seven year gap, but it was the closest we were able to find (we did not want to go with the current day number of cars, 6,383, given it would be further from the truth).

    Therefore, we calculated the average energy consumption of a subway car to be 1.8 billion kWh/yr divided by 6,282 cars, or 286,532 kWh/yr.

  7. The White House

    This number was found in this article on the Daily Caller, based off an estimate from 2009 (15.5kWh/yr/sqft), which was then multiplied by the square footage of the building (55,000 sqft). As a result, we came to 852,500 kWh/yr.

  8. 5 Million miles driven in a Toyota Prius

    This number required a bit of thinking. Here were the numbers used:

    • The EPA rated the Toyota Prius’ energy efficiency at a combined 50MPG.
    • The EPA estimated that one gallon of gasoline is equal to 33.7kWh. Here’s the explanation.

    As a result, driving 5 million miles would require 100,000 gallons of gasoline, which equates to 3,370,000 kWh.

  9. The Arkansas Razorbacks’ football stadium

    The University of Arkansas’ official news site stated this number in a 2013 article. That number was 9,663,578 kWh.

  10. All of America watching the Super Bowl

    This was a very fun statistic put together by General Electric back in 2011 in this article on its GE Reports website. The number came out to 11,309,607 kWh/yr. This is a one-off calculation, but given that the Super Bowl happens once each year, we thought it made sense from a consistency standpoint to state it as a yearly calculation (kWh/yr as opposed to kWh).

  11. The Indianapolis Zoo

    Because the Indianapolis Zoo partnered with the EPA, we’re able to access information about its energy use on the public EPA website. There we find a consumption of 13,512,800 kWh/yr (and it’s all green!).

  12. The country of Jamaica for a day

    This was a tricky calculation, as we had to come to terms with the fact that it wouldn’t be 100% consistent with the formats of the other data points (all yearly calculations), but for some smaller countries in the world, the amount of energy from these panels could add up greatly when looked at a more granular scale (daily vs. yearly use).

    The number for this was pulled from The World Factbook (put forth by the U.S. Central Intelligence Agency) and organized into a more usable format by Wikipedia. It has numbers for nearly all countries. For Jamaica, that was 6,400,000 MWh/yr, which comes out to 17,534,247kWh/day.

  13. The Sydney Opera House

    Lastly, the number used for this calculation came from a July 2010 issue of an Australian engineering magazine.