Solar photovoltaic (PV) system is often considered the most reliable and clean energy source amongst all the renewable energy sources. The PV modules generate electricity, converting sunlight.
A well-designed solar PV system can produce sufficient energy to satisfy the power requirements of your residence, office, or factory.
With a solar PV system, you’ll produce enough power to cut your electric bill drastically. If you’re in a sunny region, you can even reduce electric bills by up to fifty percent as well!
The average electricity cost for a house in the United States of America (USA) is $1,450 annually. A 6 kilo watts solar PV system in a state (Washington) of the USA can make a savings of $692.5 a year.
But for a more significant financial return, you must know precisely how to calculate number of solar panels required for your house.
Installation of a solar PV system without prolonging the process is another prime concern here. This investment can be just as costly as the one you’d make in real estate.
Continue reading till the end of this article to find out how to calculate number of solar panels required for your house for a super saving. So, you can eliminate all sorts of extra expenditures from day one of solar PV system installation while minimizing the carbon footprint as much as possible.
You can rely on a solar installation firm, of course; you can attempt this DIY solar as well. Since we will provide you the reasoning of our methods and all other significant details on this matter, How to Calculate the Number of Solar Panels Required for Your House or property.
Three Factors towards How Many Solar Panels Are Needed to Run a House?
The sum of solar panels you require for your house varies with the circumstances you’re in.
The three most significant factors for calculating number of solar panels required for your house are as follows:
i. Energy usage per year / month / daily in kWh
ii. Geographical location for sun hours per year / month / daily
iii. Size and capacity of solar panels
Three Steps: How to Calculate the Number of Solar Panels Required for Your House?
The number of solar PV panels required depends on several factors. Let’s consider them one by one:
Step 1: How Much Energy Does Your House Require Yearly?
Work out the annual electricity consumption (kilowatt-hours, kWh) on your first step of how to calculate number of solar panels required for your house.
If you look at your monthly electric bill, you can find this vital piece of information. Please take this as average monthly usage and multiply it by 12 to determine your annual kWh usage.
This, obviously, is an easy approach; however, your electricity consumption in summer will vary significantly from winter.
Add up the electricity usage going over the electricity bill of 12 months for a better approximation of annual electricity consumption.
Lets’ say,
The Annual Electricity consumption of your house = 5,565 kilo watts hour (kWh)
So, how much solar power will you need monthly / daily / hourly?
Now, we determine the monthly, daily, or hourly average consumption to calculate how much power you will require to produce from solar PV panels.
- Monthly Average Electricity Consumption =
Annual Electricity Consumption ÷ 12
- Daily Average Electricity Consumption =
Annual Electricity Consumption ÷ 365
- Hourly Average Electricity Consumption =
Annual Electricity Consumption ÷ 365 x 24
| Average | Electricity Consumption |
| 1. Monthly | 463.75 kWh |
| 2. Daily | 15.25 kWh |
| 3. Hourly | 0.64 kWh |
You may want to add a minimum of 25 % of the measured average value to get your required power since the solar PV panels might function at lower efficiency often due to a number of reasons such as
- Cell technology: Monocrystalline vs. Polycrystalline.
The efficiency of Monocrystalline solar PV panels can be up to 20%. While, Polycrystalline solar PV panels have 17% efficiency. However, the latter one can tolerate higher temperatures.
- Roof Space: The direction at which the solar PV panels are facing if not optimum to absorb more sunlight due to roofs of an odd shape or smaller capacity, or shadows of trees or buildings, etc.
| Average | Electricity Consumption |
| 1. Monthly | 463.75 + (463.75 * 25 %) = 579.69 kWh |
| 2. Daily | 15.25 + (15.25 * 25 %) =19.06 kWh |
| 3. Hourly | 0.64 + (0.64 * 25 %) = 0.8 kWh |
Since the power requirement varies throughout the year, you’ll need to factor in your potential solar power usage to let you not waste any power. Unless, you’ve either a battery bank installed to store excess power or access to a net-metering system to pass the extra energy to the utility grid.
If you want to offset 60% of your monthly electricity consumption with solar energy, then the power you will require to produce from solar PV panels
= 579.69 kWh x 60 %
= 347.81 kWh
Assuming you have a battery bank or access to a net-metering system and your future energy requirement will not change in a decade or so, you can offset 100% (579.69 kWh) of your monthly electricity consumption with solar energy.
To acquire the exact energy measured above for powering a house with solar PV panels, the next important thing is to consider the sunlight hours in the region you’re residing in.
How many hours of daily sunlight your state receives is crucial because your geographical location and climate will affect the solar PV panels to produce energy inconsistently.
One region may not get enough direct sunlight because of the distinctive geographical location i.e., the angle at which the sunlight enters may be smaller.
So generally speaking, a house in a sunny region will require less solar PV panels to produce the same amount of power as in cloudy weather.
Step 2: How Many Hours of Sunlight Can You Expect in Your Area Per Year / Month / Daily?
The average daylight hours are not the same as peak sunlight hours.
The peak sunlight hours are a period during which the sunlight intensity is 1,000 watts per square meter.
Look at the table below to can get an idea of the peak sunlight hours in some regions.
| Region | Resource |
| 1. Australia | https://www.rpc.com.au/pdf/Solar_Radiation_Figures.pdf |
| 2. United States of America | https://www.turbinegenerator.org/sunlight-hours-rank/ |
You can find several online resources that have peak sunlight hours for other states or cities.
Go to the following website and get started by putting your specific location to find the peak sunlight hours in the result section. Here, the peak sunlight hour is described as Solar Radiation (kWh / meter square / day).
| https://pvwatts.nrel.gov/ |
For the convenience of this exercise, let’s assume,
- The average peak sunlight hours (daily) = 5
In the following step, we’ll convert the monthly / daily / hourly electricity consumption into the number of solar panels to produce the sum of energy you wish to offset annually.
Step 3 (a): How Do I Calculate the Size of My Solar System?
| Solar PV System = Average Monthly Electricity (kWh) Consumption / (Peak Sunlight Hours x 30 days) |
Putting the values we’ve got above to formulate the sizing of your solar system,
Solar PV System = 579.69 / (5 x 30)
= 3.8646 kW
Now, when the generated electricity goes through the conversion of Direct Current (DC) to Alternative Current (AC), we need to take into account of Derate factor which is the ratio of loss while converting DC to AC. The Derate factor is typically 0.77.
| Solar PV System = Average Monthly Electricity (kWh) Consumption / (Peak Sunlight Hours x 30 days x Derate factor) |
So, the Solar PV System becomes = 3.8646 kW / 0.77
= 5.02 ~ 5 kW
Here,
- The Average Monthly Electricity (kWh) Consumption = 579.69 kWh.
- The Peak Sunlight Hours (monthly) = 5 x 30 = 150
- Derate factor = 0.77
Step 3 (b): Determining Individual Solar Panel Sizing
The power rating, i.e., the wattage of a solar PV panel, indicates how much power it can produce.
Assuming,
Power Rating of the Solar PV Panels = 250 watts
| The Number of Solar Panels Required = Solar PV System Size in Watts / Power Rating of the Solar PV Panels |
Thus, The Number of Solar Panels Required
= 5 x 1000 watts / 250 watts
= 20
If your house can’t support or allow enough rooftop space for solar panels, you may install solar PV panels of a higher power rating.
Considering solar PV panels of 300 watts power rating,
The Number of Solar Panels Required
= 5 x 1000 watts / 300 watts
= 16.67 ~ 17
Conclusion
Solar PV system as one of the sources of renewable energy is very much encouraged in factories, hospitals, residential applications, etc. to lessen the emission of carbon dioxide to the atmosphere as much as possible.
With a solar PV system that generates electricity by converting the sunlight, you can reduce electricity bills heavily, ensuring you’re empowered and have good riddance with all the nonrenewable energy sources!
In this article, we’ve tried to equip you in few steps to determine the best combination for efficiently generate solar power and maximize your investment.
Largely, How to Calculate the Number of Solar Panels Required for Your House necessitates you to weigh the aspects of weather conditions (such as dust, wind, snow, etc.), solar PV panel efficiency, surface angle, and, orientation, etc. and make proper measurement of your energy requirement throughout the year and peak sunlight hours in your area.
Summary of How to Calculate the Number of Solar Panels Required for Your House (Key Takeaways)
- Step 1: Take your previous electricity bills to calculate your average yearly / monthly daily / hourly power consumption and factor it according to your power generation goal
- Step 2: Divide the average monthly electricity (kWh) consumption (kWh) by the peak sunlight hours (of your region) per month and then further divide it by 1000 to get the solar PV system size in watts
- Step 3: Divide solar PV system size by the power rating (wattage) of your chosen solar PV panel capacity to get the number of solar PV panels required for your house