How does solar power work?

Thinking about making the switch to solar energy? Join the club! 

As solar technology continues to become more affordable, more and more Kiwis are harnessing the energy of the mighty sun to power their homes. More than 26,000 New Zealand homes are already hooked up to solar power, according to figures from the Electricity Authority. 

While cleaner energy and lower bills definitely sound appealing, it’s important to understand how solar works before committing to a solar panel installation. In this blog post, we’ll show you exactly how solar technology works and answer some of the most frequently asked questions people have about solar energy. 

Solar power 101

Let’s kick things off with a quick science lesson.

The sun produces an astonishing amount of energy. In a single hour, about 430 quintillion joules of energy from the sun hit Earth - that’s 430 with 18 zeros after it! For context, the entire global human population uses about 410 quintillion joules of energy per year.

Photovoltaic (PV) panels are used to convert some of this energy into electricity. When sunlight hits a PV panel, photons (particles of light) knock electrons loose from the atoms of a semiconducting material such as silicon. 

The movement of these electrons generates a flow of DC electricity, which is then sent to an inverter where it’s converted into AC electricity (the kind of electricity used to power your lights, appliances, devices and anything else you plug into the wall). The AC electricity is then delivered to your switchboard, where it can be distributed throughout your home. 

The advantages of solar power 

• Better for the environment: Harnessing the energy of the sun is a sustainable and environmentally friendly way to power your home. Solar power produces no greenhouse gases and allows you to use the sun’s endless supply of energy without worrying about depleting precious resources. 
• Cheaper power bills: Generating your own electricity reduces your dependence on the grid and ultimately leads to cheaper power bills. The amount you’ll save depends on the amount of power your system generates, your electricity rates and how much solar power you can use. 

Solar power FAQ

Which regions are best suited to solar power?

Many parts of New Zealand are suitable for solar power. It’s a particularly good option for the sunnier parts of the country, including Auckland, Northland, Nelson, Bay of Plenty and Marlborough. Remember that solar panels rely on sunlight rather than heat, so you don’t necessarily have to live somewhere warm to enjoy the benefits of solar power. 

Do solar panels work on cloudy days?

Solar panels work best in clear, sunny conditions, but they do still produce electricity even when it’s cloudy - they’re just not as efficient. As a general rule of thumb, a solar system will generate about 10-25 percent of the energy it would in optimum conditions. Solar panels produce no electricity at night. 

Is my roof suitable for solar panels? 

Solar panels are typically installed on the roof of your home. In the Southern Hemisphere, solar works best on north-facing roofs and may also be suitable on roofs with an east or west orientation. Mounting frames can be used to adjust the angle of the panels to increase sun exposure, but they can drive up the cost of your installation.

In addition to the orientation of your roof, you’ll also need to consider shade. Trees, hills and nearby buildings may cast shadows on your roof, which will affect the efficiency of your solar panels. It’s important to think long-term here as well. How tall will your neighbours’ tree be in 10 years? Is it possible that tall buildings will be constructed in your area in the years ahead? 

Will solar power allow me to live off-grid?

The majority of houses with solar will still need to buy electricity from a retailer. Solar systems do not generate electricity at night and may not produce enough electricity in the day to cover your household’s needs. Most people remain connected to the grid so they can purchase electricity to cover any energy deficits. 

Some solar power setups include batteries, which are used to store solar-generated electricity and provide power when the panels aren’t generating enough electricity to meet demand. However, the high cost of batteries means this usually isn’t a good financial choice for most households. 

How long do solar power systems last?

Solar power systems are built to last and, in many cases, will work without a hiccup for decades. Many solar panels come with a 20+ year performance warranty and a ten-year manufacturing warranty, while workmanship warranties can vary between installers. Solar inverters (the component responsible for converting the solar-generated DC electricity into AC electricity) typically have a lifespan of about 10-15 years. 

What’s the payback period on a solar power setup?

Over time, the amount of money you save on power will probably exceed the cost of your solar installation. The payback period can vary significantly depending on the size of your solar power setup, your location, your electricity usage habits, your electricity rates, the orientation of your roof and more. You can use the Energywise Solar tool to get an estimate of your return on investment.