Solar Panels

How Many Solar Panels Do I Need?

By April 11, 2021No Comments
how many solar panels do i need

How Many Solar Panels Do I Need?

When planning to install solar panels on a property, owners are faced with the task of making certain decisions. One of the questions to ask yourself before installing a solar PV system is, how many solar panels do I need? For future reference, PV stands for Photovoltaic, which is a Greek word; ”photo” = light and ”voltaic” = voltage.

Knowing the exact number of solar panels you need for your home or business ensures your system is sufficient to produce enough power for your needs.

The major factor determining how many solar panels will sufficiently power a home is its annual energy usage. This can be sourced from your home’s electricity bill.

Also, the average annual electricity usage depends on factors like the home’s size, the number of occupants in it, and their energy habits.

Annual Energy Usage

Before you can answer the question of how many solar panels do I need, your average annual electricity usage is one value to have with you. Energy usage is a measure of how much energy a home uses and is measured in kWh. This unit is not the same as kW (kilowatt), used in measuring power.

How Many Solar Panels Do I Need: Calculation

Once you have checked your electricity bill for your average annual energy usage, you can forge ahead to calculating how many PV panels you need. Solar panels are rated in power output, which is measured in watts (W). Most solar panels have this rating ranging from 245W to 400W.

Your home electricity demand will determine which rating to go for. PV panels with larger outputs are suitable for properties with higher electricity demand.  A property with a high electricity demand will do fine to go for panels with a power output rating above 325W. This ensures it has more with fewer panels.

Most homes and businesses have an average energy usage of 3,800 kWh per year. The number of solar panels needed to meet this will depend on their power output. Taking a 400W solar panel as an example, 10 PV panels will be required to meet this energy usage.

Also Read: What is LiFePo4 Battery?

Similarly, a home with an average energy usage of 2,000 kWh per annum will require 5 PV panels with a power output of 400W.

However, if your interest is in solar panels of lower power output, then you will need more PV panels.

Revisiting our last example, to meet up the power need of a home with an average output power of 2,000kWh per year using 240W solar panels, 8 panels will be required to get the job done.

The table below gives solar PV sizes, the estimated annual output to expect, and the number of panels needed. This helps you determine the right answer to the question of how many solar panels do I need.

However, note that this table uses 400-watt panels and the figures will change with the power output of the panels.

Size of Solar PV System Estimated Annual Output Number of 400 Watt Solar Panels
1.2 kW 1,200 kWh 3
2 kW 2,000 kWh 5
3.2 kW 3,200 kWh 8
4 kW 4,000 kWh 10
how many solar panels you will need will depend on your energy usage needs

How many panels you will need will ultimately depend on your energy usage needs.

One common setback of solar panels with higher power output is higher costs. While you get higher energy from fewer panels, you spend more on investing in them. This is why, you might want to consider going for PV panels of low power output.

The table below shows what to expect from 250 watt solar panels.

Size of Solar PV System Estimated Annual Output Number of 250 Watt Solar Panels
1 kW 1,000 kWh 4
2 kW 2,000 kWh 8
3 kW 3,000 kWh 12
4 kW 4,000 kWh 16


Note that your solar PV system does not necessarily need to meet your total energy need. How is that? Well, you can install a system that only meets a portion of your energy usage. This will ensure you do not totally rely on your supplier for electricity, cutting back on your electricity bill. As time goes on, you can add to your system’s size, increasing its capacity without any interruption to the existing system.

Consider Your Specific Needs When Sizing PV System

As you have probably learned from this guide, there is no “one cap fits all” answer to how many solar panels you need. This is because the right answer varies from property to property, depending on factors like the property’s energy demands and the PV panels’ power output.

Now, let’s use the average flat as an example. Studies show that the average flat has an average annual energy usage of 2829 kWh. In this example, we will use 320W PV panels.

The average annual energy usage shows that the house needs a system with a total annual power output of 2,829 W. The number of solar panels needed to get this is given by dividing 2,829 by 320, giving us 8.8. This means that 9 units of 320 W panels are needed for a flat with an average annual energy usage of 2,829 kWh.

If your electricity consumption increases at a future time, you can simply increase the number of PV panels on your roof (given you have enough space).

Pick Accredited Installers

You should always speak to your local PV panel installer for further guidance. Be mindful of selecting an installer who has an accreditation to install this renewable energy technology. It is because accredited installers are trained to meet the industry standards. Furthermore, they are required to have business insurance should any of their installations fall below the standard. This will give you a piece of mind that any potential issues can be dealt with accordingly. In the end it is your property and you should always make sure you have all the corners covered.