5kW Solar Power System - Everything You Need to Know

On our planet Earth, there are dozens of ways energy can be generated and utilized. Since the day we discovered fire, we have made incredible technological progress, and now have a multitude of energy technologies at our disposal. And yet, one technology stands apart from the rest - solar power. 

The beauty of solar power lies not only in the fact that it is clean, reliable and astoundingly cost-effective, but that it is extremely flexible. Solar cells can be employed to power a tiny wristwatch, as well as a gigantic space station or an entire city. 

But let us talk about homes. Many homeowners ask us what the typical size of a solar power system is. Although the required size of a system depends on many factors, the majority of homes in New Zealand can be powered with a 5 kW solar system, making it one of the most common system sizes.

Therefore, we decided to break down all the aspects of a 5 kW system, including its cost, number of panels, energy production, etc. Let’s dig in.

How Many Solar Panels Does a 5 kW System Have?

About fifteen years ago, the most powerful solar panels could generate about 200 W (watts) of power. So, for a 5 kW system, you would need 5,000 W ÷ 200 W = 25 solar panels. Fast forward to 2022, and the most common sizes of solar panels are 400 W to 450 W. This means only 12-14 solar panels would be sufficient to generate close to 5 kW of power.

Interestingly, this does not mean panels have doubled their physical size. Instead, solar panels today can generate twice the power in nearly the same size and weight. In other words, solar cells have become way more efficient, thanks to consistent research worldwide. 

A couple of decades ago, 11 or 12% efficiency was the norm in solar modules. Today, solar modules with 25% efficiency are not unheard of.

How Much Energy Does a 5 kW Solar System Produce?

When one says ‘5 kW’, it is a measure of power (electricity generated per hour). Also, this number is the maximum power a system can generate in ideal conditions. This is why a 5 kW system is also mentioned as ‘5 kWp’, where the ‘p’ stands for peak power.

Naturally, knowing just the power rating is insufficient, since it is tied to the ‘ideal conditions' mentioned above. For instance, a 5 kW system located in Auckland will receive different levels of sunshine than one located in Dunedin, thus generating different amounts of energy. Therefore, understanding the energy generation from a system is as important as understanding its power rating.

The energy generation depends on what we call the solar radiation for that location. In other words, the energy generated by a system is proportional to the duration and intensity of sunlight received. 

Below is a table of the irradiation levels of some of NZ’s major cities, and the energy generation from a 5 kW system in each of them.

One thing to remember is that the above numbers consider an ideal or perfect system. And a perfect system means clean, dust-free solar panels with sunlight falling perpendicular on every panel. Unfortunately, somewhat like humans, complete perfection is unattainable. 

For instance, solar panels should ideally face North for optimum generation, but you may not have a North facing roof. Or, you might have a North facing roof but its inclination is not perfect, or you may have a roof that is partially shaded during some part of the day.

In any of these cases, the energy generation from your system, and the subsequent savings, may vary. You can use our solar calculator for a much more accurate and personalized calculation of energy production, cost, and savings.

How Much Roof Space is Needed for a 5 kW Solar System?

Just as panels have gotten more powerful (in other words, smaller), the space required for solar systems is also smaller. Today, a 1 kW system requires about 8 sq. m. space on your roof. Therefore, a 5 kW system will take up to 40 sq. m.

However, this does not automatically mean that every roof with over 40 sq. m. can install a solar system. To get 5 kW from an awkwardly positioned roof, you may have to install a larger system. Besides, if your roof is shaded by a tree or a nearby building, the shaded portion will not be useful for installing solar panels.

Thankfully, most homes in NZ have enough shade-free space to go solar. 

What are the Other Components of a 5 kW Solar System?

Solar panels are the key component of a solar power system, but they alone cannot power your house, at least effectively. Let’s look at the other components which, together with the solar panels, make up the entire system.

1. Inverter

Solar panels are DC (direct current) devices, while your appliances run on AC power. To convert direct current from the panels to alternating current, you require a device called an inverter. The inverter converts the current type while also modifying the voltage and current values so as to make them suitable for your appliances. 

A Fronius Primo String Inverter

Currently, there are two main types of inverters available in the market - string inverter and micro-inverter. A string inverter, such as one shown above, is connected to an entire string of solar panels, and converts DC power of all the panels in the string to AC. 

Enphase Micro-inverters installation layout on a roof

A micro-inverter, on the other hand, is a tiny device that connects itself to each individual panel and converts DC to AC at the panel level. Micro-inverters are more expensive, but offer several advantages - if one panel stops working or underperforms, the other panels are unaffected. 

They also allow a more complicated arrangement of solar panels on a roof that’s not ideal. Overall, microinverters guarantee better performance from pretty much any solar system.

When selecting an inverter, installers choose a size that correlates to the size of the solar panels. For instance, a 5 kW inverter pairs with a 5 kW set of solar panels. Installers also look at the input and output voltage of the inverter. For example, larger systems may need inverters with a three-phase output instead of a single-phase.

Modern inverters come with a host of features such as built-in safety sensors, bi-directional metering capability, and remote monitoring via Bluetooth or Wi-Fi. Off-grid or hybrid inverters also include electronics that optimize battery charging, such as an integrated MPPT charge controller.

2. Batteries

The only major limitation of solar power is its intermittency. Sunlight appears and disappears with day and night cycles and sometimes even with cloudy weather. 

With the advent of grid connection, it is easy to combine the pros of solar and grid power while eliminating the limitations of both. Grid connection allows you to use grid power during the night (or non-sunny days), and to send excess solar power into the grid when you don’t need it.

A Tesla Powerwall Lithium-Ion Battery

But when you require independence from the grid, batteries have been a proven remedy for the absence of solar power during nights or overcast days. Batteries convert electrical energy into chemical energy and can store it for significantly long durations.

You can choose between the traditional lead-acid batteries or the more modern lithium-ion batteries. Li-ion batteries are superior to lead-acid - they are more energy dense and hence lighter. They also have extremely low maintenance, a longer life, and safer operation, all of which justifies their higher cost.

A battery’s capacity is measured in kWh, and you can choose from a wide variety of specs and features when buying a battery. Modern batteries offer smart features such as remote monitoring and load optimization. They also come with a host of sensors that prioritize safety and efficiency.

While several homeowners ask us the correct battery size for a 5 kW system, the answer is a bit more complex. The battery size depends on multiple factors. If you use most of your solar energy during evenings and nights, you will need a larger battery. The same is true if you live in a location prone to rainy and overcast conditions. 

3. Safety Equipment

Whatever your source of electricity, there is always a risk associated with it. Short circuits, surge currents, etc. threaten to damage the components of your system while also posing a threat to your own safety. Therefore, a number of safety devices are available to configure into your solar system and make it safer.

A solar disconnect switch, surge protection MCCB, and combiner box with integrated safety equipment.

This includes simple devices like circuit breakers, DC and AC disconnect switches, fuses, as well as more complex components like lightning arrestors (wherever applicable). Your installer will choose some or all of these devices based on several factors when designing your system.

4. Cables

A system’s solar panels need to be connected together to combine all the power produced by them, and then the panels also need to be connected to your inverter. Furthermore, the inverter needs to be connected to your home circuit, or batteries, if you have them.

For all these connections, you need different types of cables - DC cables, AC cables, thicker and thinner cables, and so on. Your installer calculates cable size and type based on the application, distance, etc. Many components of a solar system come with MC4 connectors to make it easy to connect or disconnect cables.

Solar Cables with MC4 connectors

How Much Does a 5 kW Solar System Cost?

Here comes the most common question - ‘what does a 5 kW solar system cost?’ Like other things, there is no definitive answer to this question. The complexity of your system, types of equipment used, etc. can impact the price tag.

However, if we were to speak about thumb rules, a 5 kW system can cost around $10,000-12,000. The impressive part is that this price is almost 80% lower than it was just a decade ago. This means shorter payback periods and higher savings!

But like we said, this is a thumb rule, and your particular house may need a system that costs lower, or higher than these numbers. The best way to find out what solar would cost you is to get quotes from more than one solar installer.

Fortunately, you can get three free quotes without an obligation to purchase through the My Solar Quotes website. And in the meantime, you can even try our ultimate solar savings calculator to get a rough pricing along with information on your system’s ROI, payback period, total savings, etc.

Can a 5 kW Solar System Charge an EV?

Electrical vehicles are taking the world by storm. Most countries are setting a deadline to the manufacturing of carbon spitting, petrol or diesel vehicles. This makes the era of electric cars inevitable.

EVs are gaining popularity for their low operation and maintenance costs, but when you pair them with solar power, the cost of using an EV becomes unbeatable. But can our 5 kW system charge an EV? This question does not have a straightforward answer.

While a 5 kW solar system can comfortably charge your EV, it may not have enough juice remaining for other appliances in your home. A way to address this issue is to oversize your system to accommodate charging power for your electric car. You can also opt for a smart EV charger that boasts of multiple useful features.

Check out our other articles on electric vehicles and solar to learn more about the topic.

Summary

Worldwide, experts are predicting a solar power explosion. Not a literal explosion, of course - but the coming of an era where solar is so practical and cost-effective that it is the obvious choice everywhere. And this change is brought about not just by large-scale solar plants, but the multitudes of residential solar systems.

This transition applies to New Zealand too, where more and more homeowners are already making the shift to solar. Among residential systems, 5 kW is probably the most common size of solar systems in the nation.

A 5 kW system costs up to $12,000 and takes up around 40 sq. m. of roof space. If designed correctly, the 5 kW system can power your house as well as your EV.

But most importantly, this 5 kW system, or any solar system for that matter, is a brilliant way to cut your power costs while improving your energy independence. And of course, the planet loves it too!