“How much solar do I need?” is a popular question. As the cost of electricity keeps going up, many Australians are looking into this alternative. But, the ideal size of your solar power system depends on several factors.
“How much solar do I need?” or “What size solar panel do I need?” These are some of the first questions customers ask when they inquire about solar photovoltaic systems. However, answering them requires careful consideration.
This is because there are various factors which will impact the number of panels you’ll need. Some of them, such as personal expectations, are under your control. Others, such as the location of your house, are not.
That’s why it’s very important to understand all these different factors. Once you do, you’ll be able to determine how much solar energy you actually need. To help you here, this article will list the things you need to consider before you can get an answer to the titular question.
Before proceeding, it’s important to be clear on one thing. When people talk about the size of solar panels, they are referring to their capacity. In other words, they are talking about the output they can deliver across the day.
The units to use here are watt (W) and kilowatt (kW). Furthermore, what matters is the total capacity of the entire system. So, a panel may have a 250W capacity and you have 20 of them. Or, they may be 350W panels but there are 14 or 15 of them. The end result is the same. You get a 5000W or a 5kW system. That is the number that matters and what you will see.
With that out of the way, it’s time to look at the different things you need to consider when deciding how many kW of solar panels you need.
How much solar do I need: Your Savings Expectations
This is the very first issue you need to decide on as it will be pivotal for everything that follows. Essentially, you need to settle on what you hope to achieve with your solar power system.
One option is to offset a part of your electricity expenses. You will choose this if you’re trying to reduce how much you’ll pay for the system itself with a focus on a quick return on your money. You’ll cover a part of your electricity needs with solar energy but still rely partly on the electrical grid.
The other choice is to try and neutralise your electricity costs. In other words, you’re trying to be self-sufficient. This involves buying battery storage and sizing up the system based on the home’s 24-hour energy usage.
You can also try to produce a lot of energy that you’ll sell back to your electricity retailer. This will allow you to benefit from the feed-in tariffs. In fact, it’s possible to have a feed-in tariff that’s around half of the price you pay for your power. This means that, under the right conditions, you can oversize the system and have very small bills.
Issues to Consider
Getting a zero-dollar electricity bill sounds like the dream. You produce your own energy and don’t pay anything to the power company. However, this isn’t the easiest thing to achieve.
This is because the output of your PV system will vary during the day. A 5kW system can only produce that much under ideal circumstances. This means a few hours on a sunny day. In other cases, your production will diminish. Naturally, you won’t be producing anything during the night.
Furthermore, your consumption will also vary. It will drop when nobody’s home, there will be spikes, and so on. All of this can make it a bit tricky to rely solely on solar.
A potential solution here is to go for an oversized system. Produce so much electricity that you always meet your needs and sell anything that’s leftover. If you have a good feed-in tariff, there is definite potential here.
Of course, there is no single foolproof solution. But, our experienced team at Solaray can work with you to examine these issues and recommend the right solution for your needs.
The Best Value for Money
When it comes to getting your money’s worth from solar panels, here’s a rule of thumb to follow.
The money isn’t in the electricity you sell. It’s in the electricity you don’t need to buy. This means you get the best savings by using up what you produce.
As such, you want to find a good balance between your production and consumption. The details will depend on your exact situation and what you want to achieve. Once again, good advice can go a long way here. Of course, finding the perfect balance is not always realistic, but you should try to get as close as possible.
How much solar do I need: Your Energy Consumption
Once you’ve decided on your savings expectations, you need some figures in order to move ahead. The first of them is your average consumption. For this, you only need your electricity bills.
You want to see how many kW you consume on an average day. If the bill doesn’t show this, it’ll show your monthly, quarterly, or annual consumption. Whatever the case, working out your daily average is straightforward.
To give you a sense of the figures you can expect, a typical Australian household will use around 20-30kWh a day. Of course, this is just a guide so your consumption may differ significantly. A person living on their own can easily slip under the 10kWh mark. On the other hand, a large household can use a lot more than 30kWh per day, particularly if there’s something like a heated swimming pool or ducted air conditioner running.
Once you know your average daily consumption, you need to calculate how many solar panels you’ll need to meet it. To get a general estimate of this, there is a formula you can use.
Roughly speaking, 1kW of solar panels will produce 4kWh of electricity per day. There are other factors which will impact this, but this is a good starting point.
So, if you use 20kWh per day, you’ll need 5kW of solar panels to meet your average usage, however it differs across the year:
How much solar do I need: Your Geographical Location
As mentioned, several factors can influence the formula from the previous section. One of them is your geographical location. This link is obvious – the more daylight hours a location has, the more efficient any solar panels will be. This is why the same panel may not perform equally well in different parts of Australia.
For example, 1kW of solar panels in Sydney will, on average, produce 3.9kWh of electrical power per day. However, if you were to consider Melbourne, the situation would be somewhat different. There, you could expect to get 3.6kWh. It’s 4.4kWh in Perth, 5kWh in Alice Springs, etc.
The point is, your geographical location matters and could mean you’ll need more (or fewer) panels to achieve the same output.
How much solar do I need: House Location
In addition to your broad geographical location, the precise location of your house also plays a role here. There are several elements to consider in this regard.
One of them is shade. Naturally, you want your solar panels to get as much direct sunlight as possible. But, the terrain surrounding your house could get in the way of this. Sometimes, you may not be able to find a spot that isn’t at least partially shaded at some point during the day. Compensating for this can mean you might need a bigger system than you initially thought, and we would also recommend microinverters.
You also need to consider your available roof space. This is important because it can determine the orientation of your panels.
In most cases, you want your solar panels to face north. This should help maximise how much direct sunlight they get. But, your roof may not allow for this.
Sometimes, the only available space may be facing south. This isn’t a deal-breaker, but it can have a marked effect on performance. Specifically, south-facing solar panels tend to be around 20% less efficient, although the pitch of the roof also plays a role here. So if you’re aiming for 20kWh, this can mean you might need 6kW of solar panels rather than five.
How much solar do I need: Peak Use
Finally, it’s not only important how much electricity you use per day. It also matters when you use it.
For example, the majority of your consumption could be in the evening or during the night. If that’s the case, then you could be wasting a good deal of the energy you’re producing. You may not get the targeted savings even if you’ve sized your solar system to your average consumption.
This might mean you actually need integrated battery storage. By storing the energy you produce, it’ll be available when you need it later on. This can make a huge difference in how much solar you end up using.
Or, you can try “load shifting”. This means trying to use as much electricity as possible during the day. So, appliances such as your washing machine or dishwasher should be on when your production is at its highest. Adding a solar battery is another thing to consider.
The bottom line is that it matters when the brunt of your consumption happens. It can help determine how much solar you need and how to make the most of it.
For more information, have a look at our detailed guide here: How To Size Up A Solar System
It’s not easy to determine how much solar energy you need. You need to decide what kind of savings you want and how that plays into your average consumption. You also need to account for your location, consumption habits, and so on. It’s not always possible to be completely self-sufficient, and it may not be cost-effective either.
If you look at the averages, a 5kW system is often the best choice. But, that won’t always be the case. What matters is that you now know what to consider. Pair that knowledge with some expert advice from a good retailer and you’ll be set.
This is where the Solaray Team can help. Thanks to the personalised advice we provide, you can find the perfect amount of solar energy for your specific needs.
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