How Efficient Are Solar Panels?

Solar Panel Efficiency - From NASA to Your Roof

NASA uses solar power in space.¹ Remember Spirit and Opportunity? These robotic rovers were sent to Mars in 2004 and exceeded all expectations of performance by using sunpower.² Both robots were equipped with solar panels that sat on top of their “wings.” These wings were designed to maximize the area of solar cells to increase their efficiency… the more sun the solar cells collected, the better the robots would work.³

These robots were able to perform better than expected because, quite simply, strong winds on Mars vacuumed up the dust that had settled on their solar panels - which gave them a 70% boost in power efficiency.⁴

The comparison between solar panels on Mars and solar panels here on earth is quite similar. If your rooftop solar panels are efficient, well maintained, and durable - they will convert more energy from the sun, you’ll pull less power from your utility, and your bill will be lower. Here at Sunrun™ that lasts for two decades, at the minimum.

Solar Efficiency on Your Rooftop

The concept is called “efficiency metrics.” Efficiency metrics measure how well your solar panels produce energy. Consumers want this information; they want to know how much energy from sunlight is transformed into electricity to make informed decisions about running a solar home. A key value point for solar consumers is maximizing energy use -- through solar efficiencies -- to save on utility bills.⁵

The average commercial solar panels on the market today run at about 15-22% efficiency.⁶ Sound low? It’s not. It’s a measurement that takes into account current technology that helps us power our homes from the sun’s rays.

If the sun produces 100% energy, solar systems are able to process 15-22% of the sun’s power into usable energy.⁷ We also use the term solar cell efficiency - which refers to the form of sunlight that can be converted - via photovoltaics - into electricity. A photovoltaic systems uses solar panels to capture the sun’s photons.⁸

Fifteen to 22% of usable energy is enough to power up your home for a significant amount of time after the sun goes down, or during a blackout or power outage when paired with a solar battery. A Sunrun solar energy system with battery storage will keep your house running even longer. And when the sun comes back up the next day? Your solar system gets recharged all over again.

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Efficiency of Solar Panels During Cloudy Days

Many of our customers ask us how efficient solar panels can be during a cloudy day. What if the sun isn’t shining at 100%? The answer is that solar panels continue to produce even when the weather isn’t clear. If there is a shadow, there is sun power. And solar panels continue to grab the sun’s rays.⁹

The sun is so powerful that your panels absorb energy from diffuse and reflected light which occurs on cloudy days. But yes, solar panels do drop production by about 10-20% of the solar panel efficiency rating.¹⁰ The important thing to remember is that cloudy locations are still a good match for a solar energy system.

Solar Panel Efficiency During the Winter

Solar panels also do quite well in the winter. But not when they are covered in snow. However, the heat that is given off by the solar panels usually melts the snow - and also gives your panels a yearly clean up from debris and dust collected during the summer.

Solar panels actually improve their performance and efficiency in winter (most machines with moving parts prefer colder weather) and they’ll even capture sunlight that reflects off the snow, which can be fairly intense.

Most rooftop solar panels face the sun and are on a slope, so they shed snow very well. Yes, they will drop production if covered in snow but the effect on your yearly production rate is very small.¹¹

What Happens to Solar Panels in the Rain?

Solar panels don’t stop producing energy in the rain. And as we mentioned above, rain cleans debris from your panels, allowing them to run more efficiently. Again, panels work best in sunlight, but this doesn’t mean they stop working in the rain. The sun’s rays still get through the rain and clouds.¹²

Our solar technicians work with you to build a solar system that is productive based on where you live, the weather conditions and your household’s energy demands.

Durability of your Solar Panels

If you’ve followed our Solar Education hub, you know that the same solar system on different homes can produce different results. Your solar panels need to be installed based on your home’s location and the amount of sun you get throughout the year.¹³ There are a number of factors we consider; trees, angle and size of roof, temperature in your area - to name just a few components. They all have a play in the durability of your system.

Renewable Energy and Efficient Solar Panels for Your Energy Needs

It is important to find a solar system company that analyzes the many components for the highest efficiency solar system that fits your personal energy needs. You want a rooftop solar system that has a long and productive life, and Sunrun can build it for you.

A professional company should guarantee your solar panel production - while ensuring that you understand the components in running a solar system that’s as efficient as possible. Sunrun has you covered with its 20-year, industry leading, solar service guarantee package.

We love to talk solar. Give us a call or get a complimentary solar quote that is specific to your energy needs. Contact us today.