© Provided by CNET Solar panels are a big investment, and you don't want to invest in something that won't be as good as it is in a few years. But solar panels lose their efficiency very slowly, so you might not know it. Jenna Wagner/Getty ImagesResidential solar power has exploded in recent years as more Americans consider switching their energy consumption to renewable sources (especially in light of the new federal tax credit).
If you're one of those solar naysayers, you wonder how long your solar investment will last and how efficient your solar panels will be in 20 years. The good news is that your dashboard will continue to work well into the future.
Joshua M. Pearce, a materials engineer who studies solar power systems in London, Ont., said the decline in efficiency of solar panels over time isn't a major issue.
"When a photovoltaic panel or system fails, it's usually an accident, like a tree falling on your house and destroying a lot of your panels," Pierce told CNET.
Here's what you need to know about how your solar panels' efficiency changes over time.
Best solar companies of 2023: Check it out on CnetHow efficient are solar panels?
Today's solar panels have efficiencies between the mid-1920s and mid-20s. This means that when photons from the sun hit the solar panels on your roof, about one-fifth of those photons are absorbed and converted in electricity. Photons that are not converted into electricity either leave the panel (like islammed) or are absorbed but not converted into electricity. This is because most sunlight, such as in the infrared spectrum, cannot be absorbed by current solar panels.
While the efficiency of today's solar panels may not seem incredible, Pearce says the technology is surprising compared to the efficiency of natural systems.
“The most efficient biological conversion of anything from sunlight is less than 2%,” Pearce said. "We are plants that grow ten times before humans come here. We are doing very well."
After all, the efficiency of solar panels should not be consumers' primary concern. When a solar installer assesses your home, they calculate the number of panels needed to meet your home's energy needs and compensate for the efficiency of each panel.
"Each system is designed for a specific home," says Freddie Petkus, founder and owner of Critical Mass Solar, a Massachusetts-based solar contractor. "Regardless of module efficiency, we make enough modules to offset your power consumption."
How has the efficiency of solar panels changed over time?
Solar panel technology has developed rapidly over the past few decades, but we are still a long way from producing the perfect solar cell. Given this efficiency, Pierce said solar panel makers expect a failure rate of about 0.5% per year and their warranty covers panels that do not meet those expectations. However, this is very rare.
"If you look at the data, most of the moduli are below that, maybe 0.1%, and they last for over 25 years," Pearce said.
How to monitor the efficiency of solar panels
If you want to track how much electricity your solar system produces, there's an app for that. Most solar companies offer this app that lets you track how much power you're using. While this can be useful information for solar system owners, it is difficult to track the efficiency of your panels with this app.
Variations in the amount of solar energy your panels receive from day to day and year to year will negate the significant effects of reduced panel efficiency, Pierce says. "The average consumer can't afford to be 0.1% inefficient with their system."
If you want to invest in efficiency monitoring equipment, Pierce recommends installing a DC inverter or microinverter in your solar system.
Does the efficiency of solar panels improve over time with new technologies?
Technology will inevitably become more efficient and powerful over time. According to Pierce, solar panels are getting better not because of advances in technology, but because of better manufacturing techniques. These advancements create solar panels with better glass that absorbs more solar energy, thinner metal layers for more cells, and better metal contact placement.
A more efficient cell would be darker and blacker, Pierce said, "like Darth Vader's helmet, where nothing comes out, it absorbs all the light and turns it into electricity, and you only see the evil in it."
If you want to burn your bank, all you have to do is wait for those fixes before investing in a solar system, say CNET's experts.
“Today, the payback period for solar power on a large Massachusetts utility is six to nine years,” Petkus says. "If your bill is $200 a month, I estimate you'll be paying $24,000 over 10 years." This money is better spent on solar retrofits.
Treat going solar like any other investment, says Pierce. Analyze the tariff structure of your energy supplier to calculate the return on investment of a solar system. Then try to predict future rate hikes and inflation. An estimate of around $3 per watt is a good starting point for installing a solar system. The math should speak for itself.
"The efficiency of solar cells will definitely increase, but maintaining them won't get you anywhere," Pearce said. "It's a guaranteed rate of return, because it's tax-free savings for 25 years, and it's against inflation."
