The Power of a Megawatt

The Power of a Megawatt

why IS the word “megawatt” used to describe the size of a renewable energy technology installation? We’ll level the playing field and explain what a megawatt looks like for two renewable energy technologies: solar and wind.

By Betsy Harbison

May 26, 2021

The 1 MW solar array at the National Wind Technology Center. Photo by Dennis Schroeder / NREL, 18660.

As a person who mitigates their impact on the environment, you already know that renewable energy is a critical piece to reduce carbon emissions. But unless you’re an energy engineer, you may not know how clean energy is measured or why the word “megawatt” is used to describe the size of a renewable energy technology installation. We’ll level the playing field and explain what a megawatt looks like for two renewable energy technologies: solar and wind.

If you’re scratching your head wondering, “what is renewable energy exactly?” or “how can solar panels or wind turbines create electricity?”, we recommend you read our primer. It outlines all of the renewable energy technologies that will help us get to net zero carbon emissions and then come back to this article to learn more about megawatts.

Before we dive in, let’s start with the basics.

What is a megawatt?

Things that either produce (like a power plant) or consume (like a lightbulb) electricity are measured in watts. A kilowatt is 1,000 watts. Smaller solar and wind installations will be defined in kilowatts. A megawatt (MW) is 1,000,000 watts or 1,000 kilowatts (kW), while a gigawatt (GW) is 1,000 MW or 1,000,000 kW. But to measure how much energy we use we need to look at kilowatt-hours (kWh) and megawatt-hours (MWh).

If you pay attention to your electricity bill, you have likely seen your rates calculated based on kilowatt-hours. A kilowatt-hour is equal to 1,000 watts of electricity used for one hour, which would mean that a megawatt-hour (MWh) is equal to 1,000 kilowatts — or 1,000,000 watts — of electricity used for one hour. Or, for example, if you used 1,000 sixty-watt bulbs for one hour, your utility would charge you for 1 kWh of electricity.

How many megawatts do we need?

We must understand the amount of renewable energy needed to meet our climate goals. Before 2030, we need to install an additional 1,041,000 megawatts of renewable energy globally to stay on track with the Paris Agreement.

To put that into perspective, an average home in the US consumes about 10.65 megawatt-hours each year. Keep in mind that can vary based on the climate as air conditioning will require more electricity consumption; for example, someone in Florida will use more electricity in August to cool their home than someone in Oregon. According to the 2019 census, there were 120,756,048 households in the US. That would mean that if we ignore climate fluctuations and assume average usage, the US consumes almost 13 quintillion kilowatt-hours each year! With only 12% of total US energy consumption and 20% of electricity generation coming from renewable energy sources, we have a lot of work to do to get to net zero.

Now that we know how much energy we’ll need let’s look at how solar and wind power can make an impact.

Solar Energy

Solar energy is created through the generation of solar power through solar panels. You can read more about solar energy in our renewable energy primer. To give you a brief recap, solar photovoltaic (PV) panels take the energy emitted by the sun and convert it into electricity using semiconductors. In contrast, solar thermal systems use thermal heat from the sun. Concentrated Solar Power (CSP) is a solar thermal system that uses mirrors to focus the sun’s rays to create heat, thus producing electric power.

To generate a megawatt of solar energy, you need a large space such as a huge roof or a field. A megawatt can cover 6 to 8 acres, which is roughly 4.5 to 6 football fields.

It’s important to remember that you aren’t guaranteed a full megawatt of electricity production just because you install enough solar panels to cover 6 football fields. You have other factors to consider, such as the location of the panels. Specifically, how much sunshine the panels receive and the temperature.

The best way to capture solar energy is when the sun is shining directly at the earth. The geographic location of the solar panels and season play a major role. As the time of day and season change, so does the earth’s position in relation to the sun. Thus, a location closer to the equator will have a greater number of optimal days for solar energy production. For example, California will likely have better conditions for solar than Alaska, even though Alaska will have longer sunlight hours than California in the summer. California’s closer proximity to the equator means that there will be more days when the sun is almost directly over the panels, producing more solar energy. There will also be more days in the year to have enough sun to produce solar energy.

As for temperature, all solar panels are tested at “standard test conditions” with temperatures of 77 degrees Fahrenheit. That’s not to say that the panels won’t work in colder or warmer temperatures, but the panels are rated based on those conditions.

Depending on the manufacturer, the range of electricity output for solar panels can vary. This is due to the solar panel’s cells’ ability to absorb solar energy. Three different silicon solar cells are used in solar panels: monocrystalline, polycrystalline (sometimes called multicrystalline), and amorphous. The former being the most expensive and effective, and the latter being the cheapest and least powerful of the three.

Solar power production will vary by type. There’s a difference between solar PV and thermal systems, and there’s also a difference between utility-scale solar and the solar that you’ll find on single-family homes.

Utility-scale solar systems are massive systems that are at least one megawatt. You will only find CSP systems on utility-scale solar because those systems are very large and usually found in very sunny rural or remote areas. Utility-scale solar tends to produce more electricity than smaller systems on single-family homes. This is in part due to location. Utility-scale solar will be placed in the most optimal location for solar, whereas most homeowners have to work within the confines of their existing property lines.

Current state of solar-powered electricity generation

The Solar Energy Industry of America (SEIA) and National Renewable Energy Lab’s PVWatts looked at each state’s average solar PV performance. They averaged it to determine that one megawatt of solar can power 190 homes. If you’re curious to learn how this is calculated, check out SEIA’s website.

If we were to put that into other terms, one megawatt of solar could power over 174 million* smartphones – that’s enough power for 59% of the smartphones in the US. That’s also the same as swapping 54,346 incandescent light bulbs for LEDs. That’s almost 5.5 times the number of lights in the Chrysler Building in New York (fun fact: they did a lighting retrofit in 2014 and saved 55% of their electricity costs by switching to LEDs in the building’s spire).

The US’s current solar capacity could power 17.7 million homes! But with over 120 million households in the US, currently, we are falling short.

Wind Energy

Wind energy is created through the generation of wind power utilizing wind turbines. Wind power can be generated on-shore or off-shore. Wind turbines vary in size, with offshore wind turbines being the larger of the two. The average height of an on-shore wind turbine in the US is about 466 feet, which is around 43 stories tall, with some as tall as 574 feet or 53 stories tall. Offshore wind turbines can reach greater heights. Some offshore wind turbines can be 590 feet tall, with the tallest at 853 feet — almost 79 stories. In comparison, the Empire State Building is 102 stories tall with its spire reaching 1,454 feet tall, and the Statue of Liberty is 305 feet tall or just over 28 stories tall.

On-shore wind turbines in the US are 3 megawatts on average. “Small” wind turbines can be anywhere under 100 kilowatts while utility-scale ranges from 100 kilowatts to 7 megawatts.

That difference in size also equates to a difference in wind energy production. As one would expect, wind energy production differs depending on the wind speed. Wind turbines will begin producing energy when wind speeds reach 6 to 9 miles per hour. However, they will shut off with high wind speeds (around 55 mph) to avoid equipment damage.

Current state of wind-powered electricity generation

If we were to conservatively assume low average wind speeds, one megawatt of wind energy would produce about 1,450 megawatt-hours. That would power 187 homes’ electricity use for a year or charge ~125 million smartphones. That’s equivalent to swapping out 38,947 incandescent light bulbs for LEDs. For scale, Buckingham Palace has around 40,000 light bulbs.

In the spring of 2021, the Biden administration’s approved the US’s largest off-shore wind farm’ totaling 800 megawatts, providing another 400,000 homes and businesses with access to clean, renewable power. It won’t stop there. Their goal is to have 30 gigawatts of offshore wind by 2030.

One common argument against wind energy is that wind turbines kill birds. Bird lovers, rest easy; we have good news: wind turbines do not harm millions of birds. In fact, they only account for a bit over 234,000 avian deaths a year, whereas collisions with buildings across the country account for almost 600 million.

If you are worried about other marine life being negatively impacted by the construction and operation of offshore wind turbines, you aren’t alone. There have been numerous studies to understand the impact. It turns out many offshore wind turbines can provide new habitats for fish. Additionally, areas around offshore wind turbines are protected from commercial fishing, actually protecting the marine life around the wind turbines. When it comes to marine mammals like harbor dolphins and seals, there’s actually been an uptick in their populations surrounding some wind farms, likely due to the increased food sources and reduced human interactions in the area.

Investing in a clean energy future

One megawatt can do a lot. Now that you can put one megawatt into context, it’s clear that divesting from fossil fuels is not enough. We must actively invest in renewable energy.

To power the over 120 million households in the US, we would need to install over 635,558 megawatts of solar or over 645,754 megawatts of wind, or a combination of renewable energy sources.

With the need to install 1,041 gigawatts — that’s 1,041,000 megawatts — by 2030, we don’t have time to waste. 2030 is right around the corner – less than 9 years away! Continue to take climate action and join us in our mission to get everyone invested in a clean energy future.

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*assumes 10,649 kWh/year is used by 190 homes for a total of 2,023,310 kWh

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