When starting your solar energy journey, one of the most common questions asked is ‘how many solar panels are needed to power a home?’
To determine the number of solar panels needed to power a home, several factors must be considered. These factors include the home’s energy consumption, the location and orientation of the solar panels, the panel’s wattage and efficiency, and the available sunlight in the region.
To power your home using solar power alone, it is suggested that between 20 to 25 solar panels are needed. Typically homes only have space for 12-15, which is a more accurate number and there are ways of making a more precise calculation.
How to calculate how many solar panels are needed
1. Calculate your daily electricity usage
By looking at your previous energy bills (or even easier if you have a smart meter) you can work out how much electricity you use a day. This is a much easier way of accurately working out how many solar panels are needed to power a home, as using your own bills takes into account your own circumstances.
For example, a 2-bedroom bungalow is likely to use a lot less electricity than a 5-bedroom detached house, so if you used an average or estimated electricity usage based on either of those, it is likely to give you a figure that is unrealistic to your own home. These bills will show you how much electricity you’ve used in kilowatt-hours (kWh) over a period of time.
If you’re billed monthly, you’ll need to divide your electricity usage in kWh by 30; if you’re billed quarterly, you’ll need to divide the figure by 90.
A home with a monthly electricity usage of 350kWh, for example, will use about 12kWh of electricity each day (350 divided by 30).
2. Work out the average daily sunlight hours
Next, you’ll need to work out the average number of sunlight hours per day where you live.
A quick internet search should help with this one! But as an example, here are the average sunlight hours for Belfast, Northern Ireland:
- January: 1.5 hours per day
- February: 2 hours per day
- March: 3 hours per day
- April: 5 hours per day
- May: 6 hours per day
- June: 6 hours per day
- July: 4.5 hours per day
- August: 4.5 hours per day
- September: 3.5 hours per day
- October: 2.5 hours per day
- November: 2 hours per day
- December: 1 hour per day
As the number varies from month to month, it is best to take an average for the year.
Based on the above figures, the home we are using as an example will get an average of 3.5 hours of sunshine per day throughout the year.
3. Work out the daily electricity output of a solar panel
Once you’ve figured out the average number of sunlight hours your home receives per day, you can then work out how many solar panels you’ll need.
This will depend on the wattage of the solar panels you choose. The wattage determines how much electricity a solar panel can produce. Solar panels range in size from about 240 watts up to 370 watts per panel.
To calculate how much electricity a solar panel generates, you’ll need to use the following multiplication: sunshine hours per day x solar panel wattage.
We will use a 320-watt solar panel as an example. Based on our Northern Irish home getting around 3.5 hours of sun a day, a 320-watt solar panel would produce 1,120 watt-hours or 1.12 kWh of electricity per day (3.5 x 320).
4. Divide the electricity output of a solar panel by your daily electricity usage
To work out how many solar panels are needed to power a home (covering 100% of its electricity usage), you need to divide your daily electricity usage by the daily power output of a solar panel (both in kWh).
So, based on our example, if a home used 12kWh of electricity per day, it would need to install about twelve 320-watt solar panels to generate enough power (12 divided by 1.12).
The higher the wattage of the solar panels you install, the fewer panels you will need!
Contact us for more information!
