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Solar Power Potential in New Zealand

By Aniket Bhor on in How Solar Power Works

Solar Power Potential in New Zealand

Neighbourhood showing the potential for solar on roofs

On this beautiful blue planet that we call home, enough sunlight arrives every hour to power the entire population for a year. But what about just New Zealand, you may ask. 

Of course, the solar energy potential varies from one country to another, given the differences in climate and other factors. But Kiwis are fortunate enough to enjoy ample sunlight. There’s enough solar energy here to power our homes and communities quite easily.

Let’s go ahead and discuss the NZ scenario in a bit more detail.

What Is New Zealand’s Solar Power Potential?

On average, every square metre of the country receives 4 kWh of energy per day, or about 1,460 kWh of energy per year. Now let’s do a fun calculation and find out how much solar power the country receives in relation to the required power.

New Zealand has about 268,000 km2 of land area. 

If the available solar power is 1,460 kWh/m2, the country’s power potential is 268,000,000,000 m2 x 1,460 kWh/m2 = 391280000 GWh per year. 

Now, every year, the country’s population needs about 41 TWh of energy. 

Considering both the above numbers, it’s clear that NZ requires only 0.01% of its total solar energy available. In other words, there’s about a thousand times more solar energy available than Kiwis need each year! These are exciting numbers. 

Of course, there are limitations in utilising this energy. Solar panels do not convert all light energy into electricity, a major factor being that solar panels only convert 20% of the light that reaches the panels into electricity.  Some small power losses occur in all solar power systems, such as in the wires and the DC to AC conversion, which is roughly a loss of 13% of the power generated by the panels.  So that 0.01% figure will actually end up closer to 0.06%.  Nevertheless, 0.06% is still a staggering number, and even after considering all the limitations, we can safely assume that we have far more solar energy available than we need.

Some days ago, we did a reverse calculation and found out what size of land area would be required to power entire NZ with solar. And we found out that a theoretical 24 GW solar plant located near Auckland can power the entire country. The plant would take only 192 km2 of land space - which is less than 0.1% of NZ’s total surface area. Check out the article here.

City-Wise Solar Power Potential In New Zealand

Just as solar power potential changes from country to country, it can change between different areas of the same country. In the context of New Zealand, different cities have different levels of solar potentials. Below is a heat map showing solar potential throughout the country. The darker areas on the map receive higher amounts of sunlight.

New Zealand solar potential map (source - Solargis)

It can be seen from the map that most areas benefit from an excellent solar irradiation level of about 4 kWh/kWp, meaning every kW of installed solar panels will generate around 4 kWh in a single day. 

Another way to compare solar power potential is to compare sunlight hours on a single day or over a year. The more sunny hours a city has, the higher the amounts of energy solar can generate. Here are a couple of charts that show available sunlight hours for various places on the North and South Island of New Zealand.

Place Day Annual
Auckland 6 2345
Gisborne 6 2296
Hamilton 6 2034
Kaitaia 6 2132
Masterton 6 2077
Napier 6 2318
Palmerston North 5 1772
Tauranga 7 2402
Thames 5 1975
Wellington 6 2094
Whangarei 6 2187
Akaroa 6 2161
Blenheim 7 2521
Christchurch 6 2128
Dunedin 5 1776
Franz Josef 3 1169
Greymouth 5 1846
Invercargill 5 1834
Lake Tekapo 7 2505
Mt Cook 4 1607
Nelson 7 2497
Queenstown 5 1899
Timaru 5 1918

Average daily and yearly sunshine hours in major cities (source: Current Results)

You can conclude from the above charts that a typical house in cities like Nelson or Tauranga will need fewer solar panels, as compared to a similar-sized house in Queenstown or Dunedin. This begs the question - does every city in New Zealand have enough sunlight for homes to run on solar power. And that brings us to the next section.

Solar Power Potential on a Single Rooftop

An average household in New Zealand consumes about 7,000 kWh of energy per year. Considering even the most modest solar potential of 3.5 kWh/kW/day, or about 1,300 kWh/kW/year, a typical home would need 7,000 kWh/year ÷ 1,300 kWh/kW/year = 5.4 kW solar power system.

Every kW of solar needs about 8 m2 area, as we discussed before. Therefore, a typical house needs 5.4 x 8 = 43.2 m2 of rooftop area. Houses in the country easily have an area of 100-150 m2 on their roofs. In other words, most Kiwi homes have a significantly larger rooftop area available for solar power than is usually required.

Final Thoughts

Everything that we discussed above sums into one simple conclusion - solar power potential is never a limiting or deciding factor in New Zealand’s case. We are blessed with plenty of sunshine. And this excellent solar potential seems to promote the adoption of solar.

In a report called ‘Te Mauri Hiko Energy Futures’, the grid operator Transpower forecast that New Zealand could see an installed solar capacity of up to 27 GW by 2050. Compare this to the current installed capacity of a few hundred megawatts, and the predicted growth seems explosive.

Here is another proof that the solar energy potential will never be a concern for NZ’s solar growth - the example of Germany. Germany has an average potential of 1088 kWh/m2 (much lower than NZ). Until a few years ago, Germany was the world’s leading country for solar installed capacity. Today, it has over 60 GW of solar capacity installed. 

Even if we consider the differences in GDP and population, NZ and Germany’s difference in solar capacity is still massive. If Germany can achieve this with lower potential, NZ can certainly benefit from our sunnier days. 

Fortunately, New Zealand is not only in a great position to change gears on solar power adoption, but the change is already underway. The factors that are driving this change are not just an excellent solar energy potential, but the consistently rising electricity costs, and an ever-looming climate emergency.

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