One of the most common mistakes homeowners make when buying solar systems is not considering what size fits their needs. This leads to undersized and oversized systems that don’t maximize savings. Hence, the need to know how many solar panels to power a house.
That being said, calculating the exact number of solar panels required to offset your electricity bills depends on a few things. This includes your daily energy consumption, peak sunshine hours, as well as the power ratings of your prospects.
Sounds a bit complicated, I know, but don’t worry. I’ll walk you through everything you need to get a rough estimate. Listed below are the topics I’m covering:
- You’ll need these to calculate how many panels you need to power your home
- Steps to calculate how many panels you need for your solar energy system
- Other factors you need to consider
Things you’ll need to calculate how many solar panels you need for your house:
To calculate how many solar panels you need, you need the following pieces of information:
- Your home’s daily average electricity consumption,
- The peak sunlight hours of the city you live in, and
- The power rating of the solar panels you have your eyes on.
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Daily average energy consumption
You can typically find this information on the 3rd page of your electricity bills. It’s expressed in kWh (kilowatt hours) and will be generally labeled, well… “average daily use”.
Needless to say, this figure is going to be different for everyone. But, for the sake of this discussion, here are averages from CSIRO’s statistics:
The peak sunlight hours in your region
Peak sun hours are when the sun’s intensity is at or more than a thousand watts per square meter (1000 w/m2). This is not to be confused with total daylight hours because the sun doesn’t shine at its peak intensity the entire day.
Moreover, different cities in Australia have different peak sunlight hours. For your reference, listed below are the average peak sun hours for the major cities. Although, different cities will have different values. So, if you want better accuracy, please speak with your installer.
The power rating of your potential solar panels
Again, it’s going to be different for everyone. Or, in this case, different solar panels come with different power ratings. The higher the power rating of a solar panel, the less of it you will need to get the system size you want.
For example, let’s assume you want a 6 kW solar system for your home.
- If you’re looking at a 400-watt solar panel, you will only need 15 modules.
- If you’re looking at a 300-watt solar panel, you will need 20.
Steps to calculate how many solar panels you need for your home
Step 1: Determine your solar system size
This is where peak sunlight hours and your average daily consumption come in. To get what size solar system you need, simply divide your average daily consumption by your city’s peak sunshine hours.
- Average daily consumption ÷ peak sunshine hours = System size
For example, a 4-person household in Hobart that uses 17 kWh/day would need a solar system that’s at least 4 kW to offset their power consumption. Here’s how that computation went using the equation above.
- 17 kWh/day (average daily consumption) ÷ 3.8 kW (peak sunshine hours) = 4.47 kW (system size)
Step 2: Figure out how many solar panels you need for your system’s size
This is where the power ratings of your prospective solar panels come into the equation. Simply divide your estimated system size (in watts) by the power rating of your prospects.
For example, let’s say you want to run a 4.47 kW (4,470 w) solar system and are looking at modules with 400 w power ratings. You would need roughly 11 solar panels. Here’s how that computation went:
- 4,470 w (system size) ÷ 400 w (module power rating) = 11.18 (number of solar panels)
Take note: These computations are just rough estimates
In most cases, the system size you need – and, consequently, the number of solar panels – to offset your energy bills will be higher.
This is due to factors that affect the total power generation of your system, including shading issues, module efficiency, and others. Let’s talk about them.
For further reading: Should I get more solar panels than I need?
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Other factors that can affect the number of solar panels you need
How much do you want to save on electricity bills?
How many solar panels you need will also depend on how low you want your electricity bills to be. The more panels you install, the more solar power you can generate – ultimately resulting in lower utility bills.
For example, let’s assume you have an annual electricity bill of $1485. According to our computations, a 4 kW solar system can potentially bring that down to $675 – which saves you $810 every year.
We have more projected savings profiles based on different system sizes on another blog if you want to check that out.
The orientation of your solar panels
The angle and direction your modules face also have a direct impact on the efficiency of your solar panel system. And, similar to peak sunshine hours, this also depends on where you live.
For solar panel angles, they ideally should be equal to the latitude angle of your city or state. However, any angle between 10-30° should still give your solar energy system great efficiency.
For direction, north-facing solar panels tend to perform best because Australia is in the southern hemisphere. East and west-facing panels work, too, depending on your energy usage patterns.
South-facing panels produce the least amount of renewable energy but given the efficiency and price of modern solar systems, they should still be worth investing in.
For further reading:
- What direction should a solar energy system in Australia face?
- Are south-facing solar panels worth your money?
Shading is a common issue in rooftop solar systems, whether that’s from tall buildings in urban cities or tall trees from more rural environments. This can be a problem because shade also means that there’s less sunlight hitting your panels.
Adding more solar panels in areas that don’t have shading issues is one solution to this. Another would be to use power optimizers or microinverters instead of the more common string inverters.
Both options have their merits, so talk them over with your installer.
I hope this blog helped you figure out how many solar panels are required to power your home.
To recap, you will first need to determine the right size solar system. You can do that by dividing your daily energy usage by your area’s peak sunshine hours. Finally, you’ll want to divide your system size with the power rating of your solar panel prospects.
Granted, these variables change for everybody. If you need references, though, you’ll find averages for energy consumption, peak sunshine hours, and all the equations you can use. Just scroll back up.
But, if you don’t want to go through the hassle that comes with math (I don’t either), our network of pre-vetted installers can get that done for you. We can ask them for 3 FREE quotes right now if you want.