Solar Panel Selection: Key Factors for New Zealand’s Climate

Solar panels are where it all begins for any solar energy system, responsible for converting sunlight into usable electricity. Also known as photovoltaic (PV) modules, solar panels are made up of a series of interconnected PV cells that use semiconductor materials to generate an electrical current (direct current or DC electricity) when exposed to light.

Types of Solar Panels

The most common type of panel for residential/home solar systems is the crystalline silicon panel, which comes in two main forms – monocrystalline and polycrystalline. Monocrystalline panels are made from a single continuous crystal of silicon, giving them a characteristic black colour and the highest efficiency ratings. Polycrystalline panels are made from multiple silicon crystals melted together, resulting in a blue speckled appearance and generally lower efficiencies but often a lower price point.

As solar technology continues to advance, new types of panels are emerging, such as thin-film modules, bifacial panels, and building-integrated PV (BIPV). However, crystalline silicon panels remain the workhorse of the industry, offering a proven, reliable, and cost-effective solution for most applications.

You may also hear about N-Type or P-Type panels. This refers to technical differences in the type of crystalline silicon wafers which make up the so-called ‘bulk’ and ‘emitter’ regions. Generally, N-Type panels are slightly more efficient than P-Type panels.

 

Performance

Solar panel performance is typically measured in watts (W), indicating the maximum power output under standard test conditions. Residential solar panels usually range from 250W to 450W each, with 60 to 108 PV cells (or half-cut cells) per panel. The efficiency of a panel refers to how much of the sun’s energy it can convert into usable electricity, with most modern panels averaging greater than 20% efficiency with the best panels now greater than 22%.

System Design

When designing a solar power system, the number and wattage of panels needed will depend on factors like the property’s energy consumption, available roof space, shading, and local climate. Panels are mounted on the roof or ground using flush racking, tilt racking, or tracking systems that follow the sun’s movement.

They are then wired together in series to form ‘strings’. In turn, these strings can be connected in parallel before being fed into a MPPT (maximum power point tracking) solar controller (often called a charge controller). Solar controllers are sometimes standalone units which vary the direct current (DC) electricity from the panel into DC electricity that meets the input requirements of either a battery or inverter downstream of it.

Solar controllers can be built directly into inverters. The inverter’s fundamental purpose is to convert DC electricity to AC (alternating current) electricity that we use in our daily lives, but some inverters can also charge a battery, either by passing the DC electricity from the panels straight through to the battery (at a specific voltage that is required for charging the particular battery) or by converting AC electricity into DC electricity (batteries only charge and discharge DC electricity). An inverter that has solar controller functionality, converts DC to AC, charges a battery and is grid compatible is called a ‘hybrid’ inverter.

Solar Panel Lifespan

The lifespan and durability of solar panels are key considerations, as they are exposed to the elements year-round. Most quality panels come with performance warranties of 25 years or more which mean they will still be producing somewhere between 80 and 90% of their rated power (depending on the warranty) at the end of this warranty period. The panels are designed to withstand hail (typically up to 25mm hailstones), snow, wind, and temperature extremes. Reasonably regular cleaning and inspection should help maintain panel performance over time.

Key factors to consider when choosing solar panels in New Zealand

Most modern solar panels will work well in New Zealand. Here are some key factors to look for in solar panels for the conditions here:

Efficiency

Naturally efficiency is important. However, while a high efficiency panel is definitely desirable, there is a premium for the absolute state of the art panels which doesn’t stack up for most people on a watts per dollar basis. Most NZ installers currently install panels providing between 400W and 440W of peak output, this being the sweet spot between high efficiency and value. Efficiency and, therefore, panel ratings are also improving all the time as the technology advances.

Temperature coefficient

The temperature coefficient of a panel is the measure of how much the performance degrades with each degree warmer the panel is (the standard test condition is 25 degrees, panels often get warmer than this even if the ambient temperature is lower). Panels with a low temperature coefficient are better able to maintain their performance in hot weather. Look for panels with a temperature coefficient of -0.35%/°C or better.

Durability

NZ’s weather can also be harsh on solar panels, with high winds and hail. While snow is rare in the Nelson, Marlborough and Tasman regions, it is an important consideration elsewhere in the country – especially off-grid, high-country installations. Choosing panels with robust construction and high wind and snow load ratings can help ensure they withstand the elements over their 25+ year lifespan. Look for panels with a wind load rating of at least 2400Pa and a snow load rating of at least 5400Pa, especially if your installation is in an area prone to heavy snow.

Low-light performance

While the top of the South Island is one of the sunniest places in NZ, there can still be cloudy and overcast days. Panels with advanced cell technologies like PERC (passivated emitter rear contact), bifacial design, and half-cut cells can help maintain output even in low light conditions. For those lucky enough to be in the Nelson/Marlborough region, low-light performance may be less of a priority compared to other factors like efficiency and durability.

Warranty and quality

Given the long-term nature of a solar investment, it’s important to choose panels from reputable manufacturers with strong warranties and quality control. Look for panels with a product warranty of at least 12 years and a performance warranty of at least 25 years, guaranteeing a minimum output level over time.

 

Key takeaways

Solar panels are the heart of any solar energy system, transforming sunlight into clean electricity. Whether you choose traditional crystalline panels or cutting-edge thin-film designs, it’s crucial to consider efficiency, durability, low-light performance, and warranty when selecting panels for New Zealand’s diverse climate. But a successful solar system goes beyond just panels – effective design that accounts for your unique energy needs, space, shading, and local weather is key to maximising performance and returns. By partnering with experienced solar professionals to create a tailored solution, you can fully harness the power of solar.

As technology advances and more people recognise the environmental and financial benefits of solar, New Zealand’s renewable energy future looks bright. By embracing solar power, Kiwis can reduce reliance on fossil fuels, cut emissions, and build a more resilient energy framework. With the right panels, design, and support, solar energy has the potential to revolutionise how we power our homes, paving the way for a greener, more prosperous future for all.