In this article, you will learn how to calculate how many solar panels you need for your home.
The growth of solar power over the past two decades has been staggering. In fact, the average annual growth since 2000 is nearly 40%.
So if you’re thinking about solar panels for your home then you’re not alone. To be honest, this demand has helped to reduce prices and make this energy source an affordable investment.
As you know, there are a lot of questions to answer before you commit money to an installation. Knowing the size of the solar panel system you require enables you to get a rough idea of costs. Plus you’ll have a clear idea of what you need when talking to an installer.
Below we will go through the factors you should consider when calculating your solar array size and the amount of electricity you expect to generate.
Daily Energy Usage
The first figure you need to find is your total energy usage in kWh. This will be included on your electricity bill. You will have a total kWh on your bill for a monthly or quarterly period.
We can use this number to work out your daily average. For example, if you have total kWh for a month just divide this number by 30 for your daily average.
The average home in the USA uses nearly 900 kWh a month. That’s 30kWh a day.
Solar Panel Power
Next, we need to know the size and power output of the solar panels being installed.
A residential solar panel will range between 200 – 350 watts. This power might get even bigger as technology becomes more efficient over the years.
On average a home solar panel is 250 watts. That’s 0.25kW. (1kW is 1000W)
With this knowledge, we know that a single solar panel can generate 0.25kWh for each hour of direct sunlight.
Don’t worry about all these numbers right now, we’ll collect them all together later!
Peak Sun Hours at Your Home
The final key number is the amount of peak sun hour your home receives. In simple terms, this is the amount of intense sunlight your area receives in a day.
The average peak sun hours is 4 hour per day.
The amount of peak sun hours vary from region to region. These are the hours when the sun is strongest in the middle of the day. Roughly, this is between 11am and 3pm. Outside of these hours, in morning and evening the solar power output will be severely reduced. And you’ll generate zero electricity at night. You can use Global Solar Atlas to analyze solar irradiance in your region.
This is an important factor as it is when solar panels do the bulk of electricity production. So you need a system large enough to capture all your required electricity during these 4 or 5 peak sun hours.
Calculating Solar Panel Requirements
Now you have an understanding of what data you need to collect, we can calculate how many solar panels you need.
We will use the averages above but you can replace this with your own numbers.
- 30kWh daily energy usage
- 0.25kW solar panel power
- 4 hours peak sunlight
Start by working out how much electricity you need to produce each hour. Divide daily energy use by peak sunlight hours.
30kWh ÷ 4 = 7.5kWh.
Now we know our solar panel system needs to produce 7.5kW of power. To find out how many solar panels this needs you divide 7.5 by solar panel power.
7.5kW ÷ 0.25 = 30.
To run the average home you need 30 solar panels.
Space Required
While it is possible to use solar panels to generate electricity for a whole house, most people don’t install a system so large. This is because it requires a lot of space (and investment).
Most homes will have an array of between 18 – 21 solar panels. This delivers a decent amount of electricity to reduce utility bills but doesn’t fully offset all electricity usage.
Just in the required space for a 30 solar panel system, you’d need 500+ square feet of sunny roof space. Most properties don’t have this available.
In addition, the numbers calculated above don’t take into account factors such as shading from trees or obstacles, cloud cover, degradation, and adverse weather which all reduce a solar panel system’s output. So you are always likely to draw extra energy from the main grid when solar power doesn’t meet your needs.
Other Considerations
The calculations above are useful to give you a rough idea of how much electricity you can produce in your area. You should still consult your solar installer for more accurate and bespoke calculations. Plus these companies will be able to spot any potential issues and design a suitable system for you.
It’s always best to use an installer with plenty of local knowledge as they will be able to take into account multiple factors at your home including:
- Peak sun hours
- Local weather and climate
- Orientation and roof angle
- Direct sunlight and shading
- Local electricity costs
- System design and suitable roof space
- Solar panel weight and roof strength
How Many Solar Panels Do I Need Summary
I hope this article helps you work out how many solar panels you need for your home.
Solar power is an effective way to reduce your utility bills and your carbon footprint. You’re probably keen to get as many solar panels as possible to take full advantage of these benefits. You can use the information above to give you a guide on the amount of electricity you could produce on a sunny day.
Thanks for reading.
