As more people become aware regarding the negative effects of conventional energy sources on the environment, and with energy prices rising, a lot of homeowners are switching to solar energy. But how can you calculate the required amount of solar panels in order to power your home?
The energy consumption of your household, the size and efficiency of the solar panels, location of your home, and the amount of sun in your area will determine how many panels you need. In this article, we will discuss these elements and give you a ballpark figure on the number of solar panels you need for your residential property.
This is the most crucial step in figuring out the number of solar panels required, which is predominantly how much electricity your residence consumes. This metric is present in your electricity bill and is expressed in kilowatt-hours (kWh).
For example, in case your monthly consumption is 900 kWh, that is the total amount of energy you need to produce from your solar panels on a monthly basis.
Every solar panel has a power rating which determines the amount of energy that can be generated under perfect circumstances. Most solar panels today are rated between 250 and 400 watts per panel, with an average value being 300 watts.
The amount of energy that a solar panel can produce is dependent in part on the following:
Solar panel efficiency: High-efficiency panels produce more power.
Sunlight hours: Energy production is greatly influenced by the number of hours of direct sunlight your region receives. If your area has abundant sunshine, then solar panels will be able to produce more power. On the other hand, regions that have more gloomy days, solar energy production is bound to be lower.
On average, a 300-watt panel can produce around 1.2 kWh of energy per day under optimal conditions.
Your geographical position is very important as far as how much sunlight your panels will get. Sunny places like parts of California or Arizona will need fewer panels than areas like the Pacific Northwest, which has a lot of clouds.
To begin calculating how many hours of sunlight your area receives, you can make use of tools such as the Solar-Estimate calculator, which provides a more accurate estimate based on your region. Alternatively, if you prefer calculating the hours of sunlight manually, consider how many hours are required in sunshine for your region.
As an illustration, let’s say that your zone gets around 5 hours of sun daily, then you can estimate your energy output as follows.
A 300-watt panel produces 1.2 kWh/day (300 watts × 5 hours = 1,500 watt-hours or 1.5 kWh/day).
Now we combine the data so as to determine how many solar panels a household would require. We will assume an energy usage of 900 kWh and a location with five hours of daily sun. Therefore your vicinity must have the potential to give at least 5 hours of light per day.
First, calculate your daily energy consumption:
900 kWh per month ÷ 30 days = 30 kWh per day.
Next, For calculating the amount of energy that a 300-watt solar panel is capable of producing a day, we estimate:
1 panel (under 5 hours of sunlight) produces 1.2 kWh per day.
Lastly, to find out how much energy is used daily is compared against energy for a panel:
30 kWh ÷ 1.2 kWh per panel = 25 panels.
Hence, in a month, you would need approximately 25 solar panels in order to satisfy your 900 kWh energy usage.
In case you would like to operate on your own grid or retain energy for later use during the night or on cloudy days, a solar battery storage system would be necessary. The battery size depends on your required power, how much energy you ca consume, and how much backup energy you wish to have. Moreover, energy-efficient devices are likely to increase appliances and thereby reduce the total number of solar panels needed.
Here is a table that summarizes the most important aspects that influence the number of solar panels, which is required depending on energy consumption, geographical location, and area of the panels:
Energy Consumption
Solar Panel Rating
Sunlight Hours per Day
Panels Needed
900 kWh/month
300 watts
5 hours
25 panels
600 kWh/month
350 watts
4 hours
20 panels
1200 kWh/month
400 watts
6 hours
33 panels
1500 kWh/month
250 watts
5 hours
40 panels
Other Factors to Keep in Mind
Available Roof Space: Check if your roof has sufficient space for the panels. One solar panel is usually around 5.5 by 3 feet (1.6m x 0.9m).
System Losses: Shading, inverter, and even wiring are parts of the system that might experience losses in efficiency that can be detrimental. So these should be factored in when determining your capacity, which should be increased by 10-20% to mitigate these losses.
Local regulations: Get in touch with local authorities to determine if there are any regulations, permits, or possible rebates for the installation of the solar panels.
The prices of installing solar systems are influenced greatly by the region, the amount of panels that has to be installed, the varying levels of solar panel types, and the overall intricacy of the installation. The mean cost of solar panel systems installed ranges from $2.50 to $3.50 per watt. With this, a total of 5KW would yield a range of $12,500 to $17,500 without considering deductions or rebates.
Here’s a sample different sized and cost efficient solar systems breakdown:
System Size
Estimated Cost (USD)
Energy Produced per Month (kWh)
Panels Required
3 kW
$7,500 - $10,500
400 - 500 kWh
10 panels
5 kW
$12,500 - $17,500
650 - 850 kWh
16-20 panels
7 kW
$17,500 - $24,500
900 - 1,150 kWh
22-25 panels
10 kW
$25,000 - $35,000
1,300 - 1,500 kWh
30-35 panels
The pricing includes the solar panels, inverter, batterie’s storage (when applicable), and installation. Many governments provide incentives such as credits or rebates which help subsidize the cost greatly. In the U.S for example, the federal solar tax credit enables taxpayers to write off a maximum of 26% of an installation cost.
One of the greatest benefits of solar panels is low upkeep cost and maintenance. They are less demanding after they are installed which is a great feature for homeowners. With semiannual maintenance comes in cleaning of the panels, and checking if the whole system is running in order.
Assessment: Conducting maintenance and check-ups periodically will address damage, wear and tear, and other systems malfunction problems.
Cleaning: Panel’s acceleration can be impaired by dust, dirt, and other residues compromising the overall efficiency of solar panels. Even though depending on your area, increase of efficiency may require you to clean the panels up to two times a year. In order to keep the surface intact, it is best to employ mild soap during the cleaning.
Inverter servicing: In case you do need servicing, inverters generally have a life span of 10-15 years. You have to keep a check on your inverter often to make sure the energy conversion is being conducted properly.
The cost of maintenance is usually low, and some installers may offer service packages as part of their installation deals.
For homeowners who want to maximize the benefits of their solar panels, energy storage systems, such as solar batteries, can be added to the solar setup. These systems allow you to store excess energy generated during the day for use at night or during cloudy periods. The most popular types of energy storage systems include lithium-ion batteries and lead-acid batteries.
Here is a comparison of common energy storage options:
Storage Type
Typical Lifespan
Cost per kWh
Advantages
Disadvantages
Lithium-Ion Battery
10-15 years
$400 - $750
Longer lifespan, higher efficiency
Higher initial cost
Lead-Acid Battery
3-5 years
$100 - $200
Lower upfront cost
Shorter lifespan, less efficient
Saltwater Battery
10-15 years
$500 - $700
Eco-friendly, safer than lithium-ion
Still relatively new on the market
Batteries can be especially valuable in regions with unreliable electricity grids, as they provide backup power when the grid goes down. While they can be expensive, many homeowners find that adding battery storage increases the overall value of their solar system by providing energy independence.
Over time, solar panels’ efficiency tends to drop by a small percentage. The industry standard for efficiency degradation is about one half per cent annually. This implies that by the 25th year, your solar panels will be producing only about 87.5% of the energy output relative to when they were brand new.
Consider the following example on how the solar panel output is reduced with time:
Age of Panel
Estimated Efficiency
1 year
100%
5 years
97.5%
10 years
95%
20 years
90%
25 years
87.5%
Although this reduction in efficiency is gradual, it is important to factor this in your energy planning over the long-term. Even so, solar energy systems yield significant savings even when used for more than 20 to 25 years.
Taking this into account together with the right calculations, you will know much more than how many solar panels are necessary to power your home. You will also understand the total expenses, maintenance costs, energy storage possibilities, and most importantly the overall efficiency of your solar energy system over time.
To determine the number of solar panels needed for your home, the first step is checking your energy bill and finding out your expense corresponded to average monthly electricity consumption (in kWh). Then, check the energy a single solar panel can produce given how many sunlight hours your location receives every day and the solar panel’s wattage. Now divide your total energy consumption by the energy produced by one panel to estimate the number of panels required.
Energy Consumption: The more you use electricity, the more panels you will need.
Roof Space: Sufficient space for the required number of panels needs to be available for installation.
Panel Efficiency: Efficient solar panels produce more energy and consume less space.
Sunlight Hours: Every day the panels receive sunlight corresponds to the amount of energy the panels produce.
When using a traditional 300 watt solar panel, if left exposed to the sun for five hours every day, it produces 1.2 kWh of energy every single day. The energy output depends on several factors like shading, orientation, tilt of the panel, etc. You receive more sunlight, the more energy the panel will generate.
A family living in a four bedroom house uses between 900 to 1,200 kWh of energy every month. Therefore, considering the household expenses for a month as 1000kWh, and assuming a panel produces 1.2 kWh of energy daily, 28-30 solar panels are needed.
Yes, having a battery storage system for solar energy allows you to use more power during cloudy hours or at night by storing excess energy during peak hours. Since you would be able to depend on stored energy during non-peak times, this may help reduce the number of solar panels needed. With that being said, the amount of panels implemented is still dependent on your energy consumption and battery size.
