How Sustainable Are Solar Panels?

There’s little doubt that meeting our growing energy demands with renewable energy sources, rather than carbon-heavy fossil fuels, is critical in our fight against climate change. This is one of the three main reasons people come to us with an interest in solar: to reduce their carbon footprint.

If you’re the type of person who cares about reducing your carbon footprint, then it’s likely you care about other things too. Such as what materials solar panels are made from and whether they can be recycled at the end of their long life.

So let’s take a tour through the lifecycle of a Photovoltaic (PV) solar panel to fully understand their environmental impact – from how and what they’re made from, the impact they have throughout their life, right through to how they are recycled at the end of that long life.

People are often surprised by how simple the humble solar panel is when you break it down into its core materials: glass, plastic, aluminium and silicon (not to be confused with silicone!). The first three you’ll be very familiar with, and silicon well, you’re probably more familiar than you think.

Silicon is the second most abundant element in the Earth’s crust (after oxygen) and is mined from quartz stone. There are, of course, obvious environmental impacts from mining, including local land degradation, groundwater contamination and the amount of water required during extraction and processing. It’s prized as a highly efficient semi-conductor and can be found in modern electronics including computers, smartphones, TVs and many others we use everyday. This makes it very valuable and means companies are highly incentivised to use it efficiently. As we’ll find out later, it also has the advantage that it can be melted down to be used again and again.

The next step in the solar panel’s life is manufacture – transforming those raw materials into a working PV panel. The big player here is the significant amount of energy required to power the factories that produce panels — in particular, melting down silicon to produce the crystalline silicon cell used in 95% of solar panels today. 

The exact carbon footprint of a solar panel will vary slightly depending on the technology used in manufacture and the proportion of the factory’s energy that comes from renewable sources. The more renewable their energy sources, the lower the carbon footprint of that particular panel.

The majority of the world’s solar panels, including the brands we recommend, are manufactured in China with some also being made in the US, Norway and Singapore. China leads the world both in terms of the production of solar panels, and rapidly expanding renewable energy generation. In fact, China now has more solar and wind capacity than any other country in the world. The country had 1.45 TW of renewable energy capacity online by the end of 2024 and is on track to increase its clean energy capacity fivefold by 2050.

Of course, the reality is even better than these figures suggest, as with plenty of available roof space, there’s a strong incentive for solar factories to use their own product to generate clean, emission-free energy from the roof to the factory floor. 

After the solar panels leave the factory, they’re shipped to their destination, which adds to their carbon footprint. Unlike perishable products like food, solar panels can be sea freighted rather than air freighted which offers a big carbon saving. Once they hit NZ’s shores, the panels are shipped to their destination by truck. We’re always looking to partner with companies working hard to decarbonise road freight, such as Mainfreight who have begun introducing electric trucks to their fleet.

Of course, the fun truly begins the day the solar panels are installed on your roof. From this day forward, your solar panels will begin generating clean, pollution-free, renewable energy that will recover the energy used to manufacture the panels. 

We call this Energy Payback Time. The time it takes for a solar panel to produce more power than it took to manufacture them. How quickly this happens depends on where, and how, they were manufactured and where they’re installed. Energy payback studies completed in the US, Europe and Australia all suggest this number sits around 1-2 years. Given a good quality solar system has an expected lifespan of 25 years plus, that’s plenty of time to make a significant positive contribution to overall energy.

Like any product, the longer it’s used the better its payback will be. That’s why we recommend buying once and buying right. Investing in the best quality solar panels you can afford will ensure they have a long life, and the most time to create an energy profit.

Solar panels do so much more than offsetting the energy used to create them. By transforming sunlight into clean renewable electricity, they replace other, more carbon-intensive forms of energy, to meet our growing energy demands.

While in NZ we’re lucky to have a national grid supply sourced from around 80% renewable sources, increasing demand is putting pressure on the existing renewable infrastructure. It’s unlikely we’ll see another large-scale hydro project in the near future, so more and more, we’re leaning on gas generators to make up the shortfall.  

On average globally, each kWh of conventional energy produces approximately 0.45 kg of carbon emissions. This means that in just one year, the world’s solar power systems have prevented an astonishing 58 billion kilograms of carbon emissions from entering the atmosphere.

The standard way of calculating this is by using the ‘average grid carbon intensity’. This is the average amount of CO2 emitted for each kWh of electricity produced from the grid – estimated at 110g CO2 as of August 2019 according to the Ministry of Environment. This figure irons out some big differences between coal power which emits a lot more carbon, and geothermal power which emits a lot less.

Using this figure, we can say that in terms of electricity generation alone, a standard household solar PV system installed in areas like Wanaka, Queenstown, Dunedin and Christchurch save approximately 968kg of carbon every year. Using the average production of a system installed in the Otago region, a typical 8 kW system produces approximately 9,781 kWh of clean electricity. Based on savings of 99g CO2 per kWh, solar systems installed in this region can save a whopping 968kgs of carbon.

Although New Zealand has been somewhat late to adopt solar energy, our nation currently has a total solar capacity of 270 MW, installed on farms, homes, and office buildings. Collectively, these solar systems are preventing an impressive 150 million kilograms of carbon emissions from entering the atmosphere.

A bonus carbon-saving, flow-on effect of solar panels is that they often incentivise people to further electrify their homes, slashing their carbon footprint in the process. Under the current conditions, you get a better financial return by using the power you generate than exporting it to the grid. So, if you’re generating more power than you can consume, you’re likely to start thinking about other ways to use it. For instance, you might replace your petrol car for an EV, or that old diesel boiler for an electric cylinder. In fact, this report by Rewiring Aotearoa demonstrates that it’s now cheaper to replace fossil-fuel-powered machines in your home with electric versions, especially if they’re powered by solar, than it is to keep them running.

The short answer is, yes! Glass, aluminium and silicon are all materials that can be separated and recycled. In fact, harvesting the materials from old solar panels is lucrative, with projections estimating that solar panel recycling could recoup $15b in recycled materials globally per year. 

The uptake of solar in New Zealand is still in its infancy, with an expected lifespan of 25 years plus (with reports of some still going 60 years later!) very few solar systems have yet reached the end of their lifespan. Even so, recycling facilities are already starting to pop up in NZ. Pheonix Recycling Group operate depots across NZ, including six in the South Island, and are able to recover 98% of the materials in a solar panel for reuse. 

It’s a scenario where being slow on the uptake can actually be an advantage. When we look to our neighbours in Australia, where around 30% of households have solar compared to our 2%, these facilities are becoming more and more advanced. Take a look at Gedlec, a 100% Australian owned facility based in Victoria. They are capable of recycling more than 100 panels per hour and are recycling 100% of the panel. 

It’s clear that even by today’s standards the positive contribution solar panels make over the course of their long life span, far outweighs any negative impacts associated with their manufacture and disposal. While we can’t escape some impact, excitingly, trends suggest that energy used and waste and carbon emissions produced will decrease even further in the future, as solar panel manufacturing plants, transport and recycling becomes more electrified, more renewable and more efficient.