Switching to solar power is an excellent way to reduce your electricity bills and contribute to a sustainable future. But before you install a solar system, it's important to know how many solar panels you need to meet your energy demands.
The average household in the U.S. uses around 886 kWh per month, if you're using around 1800 kWh of electricity per month, your energy consumption is twice higher than average. This may be due to various factors such as the size of your home, the number of occupants, or energy-intensive appliances like air conditioning units, electric water heaters, or home office equipment.
This guide will help you calculate the size of the solar system required, taking into account various factors like your location, panel efficiency, and system losses.
For this guide, we’re targeting an 1800 kWh solar system, which could be typical for a large family home with energy-hungry appliances or a home in a hot climate that requires more cooling. Let’s break it down step by step.
1. Calculating the Size of Your Solar System
How Solar Power is Measured
Solar panels are rated based on their capacity to generate electricity, measured in watts (W). When sunlight hits a solar panel, it produces DC electricity, which an inverter converts into usable AC electricity. The electricity produced depends on the panel’s efficiency and the sunlight it receives.
To estimate how many panels you need to generate 1800 kWh per month, you first need to calculate the size of your solar power system in kilowatts (kW).
Estimating System Size
The power generation of solar panels depends upon the weather conditions of the region you live in. Thus, the number of solar panels needed to generate 1,800 kWh per month could be different for different states.
Refer to the below graphic showing the average power generation per day by 1 kW of solar plant and average peak sun hours for different states of the US.
Therefore, in comparison to places like Texas and California, where the average peak sun hours are the greatest in the country, if you live in states like Michigan and Wisconsin where the daily peak sun hours are 3.5–4 hours, you would need 60–63% more solar panels to generate 1,800 kWh per month.
Let's take two different states with sunshine per day 5-6 hours and 3.5-4 hours.
First case: Sates with 5-6 hours of sunshine per day.
1 kW of the solar power plant can generate an average of 4.5 kWh per day in the states with 5-6 hours of sunshine per day. Hence, for calculating the number of solar panels required to generate 1,800 kWh per month following steps can be used.
Power needs to be generated per day = 1,800 kWh /30 days = 60 kWh.
Size of solar power plant= 60/4.5 = 13.3 kW (or 13 kW)
Second case: States with 3.5-4 hours of sunshine per day.
One (1) kW of a solar power plant can generate an average of 3 kWh per day in the states with 3.5-4 hours of sunshine. Hence, for calculating the number of solar panels required to generate 1,800 kWh per month following steps can be used.
Power needs to be generated per day = 1,800 kWh /30 days = 60 kWh.
Size of solar power plant= 60/3 = 20 kW
2. Determining the Number of Solar Panels
Panel Capacity and Efficiency
The next step is to figure out how many individual solar panels make up an 18,00 kWh system. Solar panels come in various wattages, typically ranging from 250W to 400W per panel. The higher the wattage, the fewer panels you’ll need.
Let’s calculate this based on an average panel size of 350W:
State with | 4.5-5 hours of sunshine | 3.5-4 hours of sunshine |
Number of solar panels | 13000/350 = 37.14 (37 Aprox) | 20,000/350 = 57.14 (57 Aprox) |
Rounding up, you’ll need around 37-57 solar panels rated at 350 watts each to generate 1800 kWh per month.
Adjusting for Different Panel Ratings
If you opt for panels with lower wattage (say 300W), you’ll need more panels. The formula is the same:
State with | 4.5-5 hours of sunshine | 3.5-4 hours of sunshine |
Number of solar panels | 13,000/300 = 43.33 (43 Aprox) | 20,000/300 = 66.66 (67 Aprox) |
Conversely, if you choose higher-efficiency panels rated at 400W, you’ll need fewer panels:
State with | 4.5-5 hours of sunshine | 3.5-4 hours of sunshine |
Number of solar panels | 13,000/400 = 32.5 (33 Aprox) | 20,000/400 = 50 |
As you can see, the number of panels can vary depending on the type you choose.
Refer to the below-summarized table for the number of solar panels required to generate 18,00 kWh per month.
State with the sunshine of | 4.5-5 hours | 3.5-4 hours |
Number of 250-watt solar panels | 52 | 80 |
Number of 300-watt solar panels | 43 | 67 |
Number of 350-watt solar panels | 37 | 57 |
Number of 400-watt solar panels | 33 | 50 |
However, to check the true potential of your rooftop, you require a solar survey.
3. Factors That Affect Your Solar Panel Count
Location and Sunlight
As mentioned earlier, not all locations receive the same amount of sunlight. Hence if you live in a region that receives less sunlight—like Michigan or Wisconsin—you’ll need more panels to compensate for lower solar radiation.
Conversely, if you live in a sunny area like Texas or Southern California, you may only need fewer panels to generate the same amount of electricity.
Roof Space
The physical space available on your roof also plays a critical role in determining how many panels you can install. Each solar panel typically measures around 18-20 square feet. If you need 37 panels, you’ll require around 660-740 square feet of roof space.
If your roof is smaller, you might have to opt for higher-efficiency panels or consider ground-mounted systems.
The Direction of Your Roof Slope
In the United States, a south-facing solar panel generates the highest amount of power. This is because the United States is located in the Northern Hemisphere of the Earth, and the SUN is always in the southern portion of the sky in the Northern Hemisphere.
Hence installing solar panels on the south-facing slope of your rooftop will generate the highest amount of power.
However, if you do not have a south-facing rooftop that does not mean that you cannot install solar panels, but that means you will need a slightly higher number of the solar panels. You need to take a solar survey to find the correct number of solar panels you need to produce 1,800 kWh per month.
Roof Angle
The power-generating capacity of solar panels is also impacted by the rooftop inclination angle. Solar panels installed on rooftops with an inclination of 20 to 30 degrees produce less electricity than those with a larger incline angle.
Again, a higher inclination does not exclude the use of solar power, but it does necessitate a larger solar system, the size of which can only be determined by conducting a solar survey.
System Losses
Solar systems aren’t 100% efficient. Various factors like shading, inverter efficiency, and dirt on the panels can reduce the output. It’s common to assume a system efficiency loss of around 10-15%. This means you might need to slightly oversize your system to account for these losses.
For example, instead of a 13 kW system, you might need a 14.3 kW system to generate 1800 kWh per month when factoring in a 10% loss.
Is Solar Right for You? Get a Custom Solar Report Instantly!
4. Costs Involved in an 1800 kWh Solar System
Cost per Watt
The cost of installing a solar power system is typically measured in dollars per watt as of 2024, the average cost per watt in the U.S. is around $2.50 to $3.50 for residential systems, depending on your location and the complexity of the installation. For an 1800 kWh system, the cost can range between:$32,500 to $45,500
These costs include the price of the panels, inverters, mounting equipment, and installation.
Fill out the form and get a No-Obligation Solar Quote
Incentives and Rebates
Thankfully, there are several financial incentives available to make solar power more affordable. The federal solar investment tax credit (ITC) currently allows homeowners to deduct 30% of the cost of installing a solar energy system from their federal taxes. There may also be state and local incentives that can further reduce the overall cost of your system.
Find Out If Your Home Qualifies for 2024 Solar Incentives – It’s Fast and Easy!
Factors that influence the cost of the solar system.
In addition to the aforementioned, you might also need to spend a little extra for the solar installation because there are a variety of variables that can affect how much a solar system costs, like the rooftop's accessibility and the battery backup. Some of the most important variables are listed below.
Rooftop type: Solar Installation cost for a flat rooftop is higher than inclined rooftop because a flat rooftop requires more structure and takes more time for installation than an inclined rooftop. However, installing on a rooftop with a higher angle of inclination needed a man-lifter crane, which raised the cost of installation.
Age of Rooftop: An old rooftop may require repairing before the installation of solar panels. Installing, solar panels on rooftops without inspection may lead to much higher repair costs.
Solar panels type: Solar panels are classified into monocrystalline and polycrystalline. Monocrystalline solar panels are more expensive than polycrystalline panels. Monocrystalline, on the other hand, is more efficient and smaller. Monocrystalline panels are preferable for rooftops with smaller shadow-free areas.
Solar inverter type: For rooftop solar systems there are two types of solar inverters are used, that is micro-inverters and string inverters. Micro-inverters are directly mounted on each solar panel, whereas string inverters are mounted in your houses and DC cables from all solar panels are connected to string inverters.
Going with a string inverter is cheap; however, the performance of micro inverters is very much better in terms of efficiency as well as in the expendability of the solar system. Furthermore, string inverters come with 5 years of warranty, whereas micro-inverters come with 25 years of warranty.
Tracking system: A tracking system tracks the weather with weather monitoring sensors as well as solar power generation. Weather tracking helps estimate the actual efficiency of the solar panels and it comes with a cost too.
However, for a household solar system, you will not have weather monitoring tracking. It is only required for utility-scale systems (>100kW)
Battery Backup: If you need battery backup with solar for backup power during a power outage then you will need to pay more for the same. The cost to pay for battery backup is subject to the size of the battery bank.
>> Get a FREE Solar quote now.
5. Making the Final Decision
Is Solar Power Right for You?
Switching to solar power is a big decision, and it's important to consider all the factors before investing. If you're looking to generate 1800 kWh per month, you now have a good idea of the system size, number of solar panels, and costs involved. Keep in mind that your specific situation—such as the amount of sunlight in your area, roof space, and energy usage—can affect the final numbers.
Moreover, with an 18,00 kWh solar system, you could save $3,824 per year on utility bills.
Long-Term Savings
Although the upfront cost of a solar system can seem high, the long-term savings are substantial. Depending on your location and energy rates, you could recoup the cost of your system in 5-10 years and enjoy free electricity for many years thereafter. Plus, going solar increases the value of your home and reduces your carbon footprint.
Solar panels release around 50g of CO2 per kWh produced during their first few years of operation. Most solar panels become carbon neutral after three years of operation. This is still around 20 times less than the carbon production of coal-fired generating sources.
Conclusion
Determining how many solar panels you need for an 1800 kWh per month system requires careful calculation based on your location, panel efficiency, and sunlight availability. By considering all these factors, you can make an informed decision and optimize your solar system to meet your energy needs.
![Top 5 Ways to Improve Solar Panel Efficiency [No Extra Cost]](https://static.wixstatic.com/media/80a440_03f2815884c043c0877f52c38ab0b66d~mv2.jpg/v1/fill/w_284,h_280,fp_0.50_0.50,q_90,enc_auto/80a440_03f2815884c043c0877f52c38ab0b66d~mv2.jpg)
Comments