Ten kilowatts is, on paper, more than enough to fulfil the daily energy needs of an average New Zealand household. If we go by the total consumption for 2023, which was 7,086.51 kWh (as per MBIE data), the daily consumption is roughly 20 kWh. A 10-kW solar power system can power said household if it runs for just two hours.

However, it’s worth remembering that solar generation systems don’t necessarily operate at their maximum capacity. Factors like location, weather, and number of sunny days can cause the output to fluctuate. These considerations determine what goes into the system, namely how many panels are required for it to be rated at 10 kW.

This guide will help you ascertain the number of solar panels necessary to achieve a 10 kW generation capacity. It’ll also be useful for reaching any capacity that can satisfy your energy requirements.

Solar Panel Efficiency

It’s a mistake to assume that solar panels output whatever they’re rated for. Most of those in the market have a solar panel efficiency between 20% and 24%, which means that a panel can reliably convert only 20% to 24% of incoming sunlight into usable energy.

Achieving 100% efficiency is impossible due to a phenomenon known as recombination. This occurs when electrons in the photovoltaic (PV) cells shift from a high-energy to a low-energy state, yielding heat or light. In fact, it’s even impractical for efficiency to reach past 33.7%, at least according to the Shockley-Queisser limit, with recombination as a reason.

Nevertheless, solar panel manufacturers need to guarantee that their panels will produce at least an acceptable amount of solar energy. As such, many offer guaranteed production of at least 90% of the panel’s capacity over its lifespan. If it falls short, manufacturers are obligated to recompense their customers either through refunds or free maintenance.

Whatever the case, solar power systems don’t always generate as much energy as they’re rated for. This shouldn’t dissuade you from your effort to discover efficient and sustainable solar power systems, however. The savings they deliver over time are real and significant.

Sizing Up The System

Now that you’re aware of how much energy a panel truly outputs, it’s time to crunch some numbers. The good news is that most solar panel installation services typically sell panels as part of the system, meaning a 10-kW system will already have enough panels included. It saves you the trouble, but let’s find out anyway.

Despite limitations to the panels’ efficiency, the market computes a system’s generation capacity based on the number of panels and their individual solar panel wattage. Assuming typical panel wattage ranges from 300 to 440 watts, 10-kW solar panel systems can be any of the following:

• 33 x 300-watt panels
• 29 x 350-watt panels
• 27 x 375-watt panels
• 25 x 400-watt panels
• 24 x 420-watt panels
• 23 x 440-watt panels

If efficiency is a major concern, you can opt to add more panels and have a system that can generate over 10 kW on paper. However, the roof space will limit the number of panels your system can have. If it can’t fit over 30 low-wattage panels, you’ll have to settle for higher-wattage ones.

Solar panel sizes are constant; the only dimension that varies is the length, which ranges from 1.6 to 2 meters. The length determines the number of PV cells in the panel, which typically come in 60 or 72-cell configurations. Having more cells doesn’t always mean the solar panel produces more power.

Do You Really Need 10 kW?

What if your roof can’t even fit enough high-wattage solar panels for your system? In that case, you need to ask yourself: “Do I really need that much to meet my energy demands?”

It may be tempting to set up the rest of the panels at ground level, a common sight among solar farms. But unless you have a yard large enough to accommodate the panels and the required rigging, it won’t be as effective as roof-mounted panels. Additionally, the building may cast its shadow on the panels, reducing their energy output during sunlight hours.

Residential solar power systems often go for 4 to 7 kW generation capacity, with the 5-kW system being the closest to satisfying an average household’s yearly electricity usage. These only need around half as many panels, allowing even small homes to enjoy the cost-saving benefits of running on solar power.

The size of your system also depends on whether you want to be partially or fully reliant on solar energy. The former option still involves paying part of the energy bill out of pocket, but the systems for this are smaller and, therefore, more affordable. The latter requires larger systems, not to mention planning for the long term.

Conclusion

If you’re set on installing a 10-kW solar kit, know that it consists of 23 to 33 solar panels (on average) and the necessary structural supports. Ensure your roof can accommodate all of them to maximise their generation capacity as much as possible.