A Different Way To Figure Out Solar Usage
If youre not interested in doing the math on your own, simply look at your utility bills to figure out how much energy youre using. Doing this allows you to multiply your energy usage by the number of hours of strong sunlight your home gets, then dividing that result by the wattage of the panels youre thinking of installing.
Factors That Influence How Many Solar Panels You Need
To determine how many solar panels are needed to power a house, several factors must be considered. For example, if there are two identical homes powered by solar energy in California and New York, with exactly the same energy usage, the California home will need fewer solar panels because the state gets more sunshine.
The following are some of the most important factors to consider when figuring out many solar panels you need:
Editors Note: This Is An Overview On How To Understand How Much Energy Your Solar System Will Produce And Overall Solar Panel Output
We always advise speaking with at least a few certified solar installers to understand how all the factors will affect solar panel output for your system.
Solar panels indicate how much power they intend to produce under ideal conditions, otherwise known as the maximum power rating.
But how much electricity your solar panels produce depends on several factors.
- Does intermittent shading obscure direct sunlight from hitting the roof?
- How much sunlight does your roof get on average?
- How big are the solar panels, and how efficient are the solar cells at converting energy?
Because the seasons and weather conditions affect the amount of sunlight hitting your roof, and the amount of sunlight also varies on the time day, you cant use just the solar panel ratings to predict how much power youll get. However, your location will allow you to do some math and determine how well a solar panel works where you are.
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Calculating How Many Solar Panels You Need For Your Home
As mentioned above, our energy experts will help you determine how many solar panels youll need. If youd like to estimate this beforehand to start your planning, heres a quick example of how you can crunch the numbers:
Say that you own an electric car and arent about to scrimp on using your air conditioning in the summer. Your average monthly electricity usage rate is a little higher than average at 1,000 kWh per month. During your energy audit, the solar representative mentions that your area receives a daily average of 4.5 peak sun hours. After discussing your options, you consider high-efficiency solar panels that can produce 300 watts per peak sun hour. Lets do the math.
300 watts x 4.5 peak sun-hours = 1,350 watts
One solar panel on your roof will produce an average of 1,350 watts or 1.35 kWh per day.
1.35 X 30 = 40.5 kWh per month .
You need a solar panel system that produces 1,000 kWh per month.
1000 kWh / 40.5 kWh = 24.69 solar panels.
Whew! That was a lot of math, but we got our answer. Your home would need roughly 25 solar panels in order to meet your existing energy needs. Youll notice that this number is actually lower than the average mentioned at the beginning of this article. Thats because we get higher-than-average amount of peak sun hours here in San Diego, and because this scenario incorporates high-efficiency solar panels. No wonder Californians love solar panels!
Let’s talk about how much you can save with Semper Solaris.
Estimate How Many Days Your Solar System Will Be Without Sun
If you don’t know this information off-hand, you can look up the annual average of cloudy days for your area online. This step is crucial in ensuring you’ll have access to your solar energy year-round. A large solar battery bank size will be best utilized in areas with more cloudy days, while a smaller solar battery bank should be sufficient in areas with prevalent sunlight. However, it’s always recommended to size up rather than down.
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The Climate Of Your Area
Well, as you might imagine, a home in a temperate climate uses less energy than somewhere colder or hotter.
In hot climates, fans do not suffice, and people turn to A/C to have a comfortable temperature around.
So, having the A/C on for most of the day will consume more energy than with a fan, right? So, having A/C at home means that you will need to install more solar power.
A small home in a mild climate area uses around 200 kWh per month. But if you go south where the A/C power demand occupies a large share of the energy consumption, that figure could go up to 1700 Kwh.
Same story goes to heating.
How Many Kwh Per Day Does A 5kw System Produce
A 5kW solar power system with an average irradiance of 4 peak-sun-hours per day will theoretically generate 20kWh per day. This assumes clear skies with no shading and will vary according to location. In practice, a 5kW system may produce less than this, as solar losses reduce the power output.
5000 watts of solar power is just about the average size of a US domestic solar system and represents 17 solar panels @ 300 watts each.
The energy output of any solar power systems depends on the suns energy, or irradiance, and this varies from state to state.
For example, the irradiance in peak-sun-hours in Arizona is 3 times more than in Alaska, so the difference van be very big. For most purposes, and estimate using an average irradiance value of 4 peak-sun-hours gives a good idea of solar output.
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Energy Storage: Solar Power Overnight
To truly go off-grid, an energy storage system is required. Domestic energy storage systems like the Tesla Powerwall are designed to store excess solar power that is generated during the day for use during night.
These systems are rated in both kW and kWh. This is because they have a maximum rate at which they can deliver power and they also have a maximum total amount of energy that can be stored in them .
The kW rating must exceed the maximum kW rating for your home , or else your home may try and pull power from the system faster than the system can deliver it, which would cause a shut down to prevent damage occurring. Note that with an energy storage system, you can get away with using less solar panels. Any sudden increases in electricity demand are compensated for by the system temporarily drawing power from storage.
The kWh value of the storage system is the total amount of electrical energy that can be stored in the system when it is fully charged. During the day, if your solar panels are generating power at a faster rate of Watts than your home is using them, the overflow is used to charge the energy storage system. Then, when the sun goes down and the solar panels stop generating, the energy stored in the system is used to power your home.
There needs to be enough electricity stored in the system to keep your home powered throughout the night until the sun comes up the next day and the panels start generating again.
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What Are The Benefits Of Installing A Solar System For The Home
Below are several advantages you may enjoy.
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Saving on utility bills
Using renewable energy actually helps you reduce your electric bill. You only need to install a PV system once to enjoy energy for decades to come.
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Lower costs of maintenance
Solar panels are durable and easy to maintain. All you have to do is to clean a few times annually, or you may even hire a professional to do it for you.
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Incentives
In the U.S.A and countries like it, the government provides financial incentives, rebates and tax credits to promote the installation of solar systems.
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Reliable energy source
You minimize your dependence on traditional power sources. This means you are not as often affected by power outages, if at all, depending upon your system.
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Clean, green energy.
By using this clean energy, you are promoting a sustainable environment. About 85% of the electricity from the grid comes from non-renewable resources which may cause environmental damage.
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How Many Solar Panels Do I Need To Power My Home Calculations Explained
There are a number of factors to consider when working out how many solar panels are required to power your home. For example the average number of hours of sunlight your home receives over the year dependent on where you live.
Also, if you want to go completely off-grid and power your home 24 hours a day, 7 days a week, all year round, then you will also need to look at energy storage, since solar panels will only generate during the day.
Or Will You What Can Affect Solar Panel Output Efficiency
The Standard Test Condition rating is based on ideal conditions converting the suns energy into power. But the solar system itself is not 100 percent efficient in converting the energy into power.
- A solar system requires an inverter to convert the Direct Current power the photovoltaic cells receive from the sun to Alternating Current power used in our homes. Power is lost as it goes through the inverter, which can be a single inverter per system, or a single inverter per solar panel. It is estimated that about three percent of electricity is lost passing through the inverter.
- Different materials used to manufacture the cells can resist the flow of electricity as can resistance passing through the cables.
- Inevitably, solar panels will pick up grime and dirt from the atmosphere, blocking full sunshine.
- Temperature can effectively create power losses as well. While it seems that a hot, sunny local would be ideal, the fact is that the STC is based on a temperature of 25 degrees Celsius . The flow of electrons across the photovoltaic cells is not as efficient at higher temperatures. All in all, solar companies estimate a de-rating factor of around 20 percent.
Be aware that system sizes are calculated inversely in the United Kingdom and the United States.
Thus, a typical 1 kWh system in the UK is estimated to produce 850 kWh unit per year, a 2 kWh would create around 1,700 kWh units per year and a 5 kWh system is estimated to create 4,500 kWh .
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The 3 Types Of Home Solar Panel Installations
Once you have matched your annual electricity demand with your systems expected energy production, you will have a clear idea of how many solar panels will be necessary to power your home.
Unfortunately, the decisions do not end there, as homeowners now have the opportunity to adopt three different types of solar panels systems: Gid-tied, grid-tied with battery backup, and off-grid installations. Below, we will take a look at the pros and cons of each one.
Whats The Biggest Electricity Consumer In Your House
Unless you have a swimming pool, your biggest electricity usage is probably for heating, cooling, or both. Because this is climate-dependant, what the average household electricity usage is depends largely on what part of the country you live in.
Because of the regional differences in climate, average household electricity consumption varies a lot from one part of the country to another. The table below describes the average household electricity usage by region.
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How To Estimate The Number Of Solar Panels You Need
So, based on these factors, how many solar panels power a home? To roughly determine how many solar panels you need without a professional assessment, you’ll need to figure out two basic things: how much energy you use and how much energy your panels will produce.
According to the latest data from the U.S. Energy Information Administration , the average American home uses 10,649 kWh of energy per year. However, this varies depending on the state. For example:
- Louisiana homes have the highest average consumption, at 14,787 kWh per year.
- Hawaii homes have the lowest average consumption, at 6,298 kWh per year.
To more closely estimate how much energy you use annually, add up the kWh reported on your last 12 power bills. These numbers will fluctuate based on factors like the size of your home, the number of residents, your electricity consumption habits and the energy efficiency rating of your home devices.
How Much Solar Power Do I Need
My advice on solar power system sizing has changed over the years due to the cost of solar panels continuing to reduce over time.
This video explains the system size providing the best bang for buck for the typical Australian household:
Spoiler alert if you dont feel like watching, my advice on system sizing is: if you have reasonable electricity consumption and a decent feed-in tariff, install as many solar panels as you can fit and afford.
This article digs a bit deeper into why my advice is to fill your roof rather than a specific size and shows how to use my nifty solar calculator to see what a solar system can do to your bills.
But first some basics.
The size of a solar power system is described by total panel capacity, expressed in kiloWatts .
A Watt is a basic measure of electrical power, and the kilo means there are 1000 of them. i.e. 1 kW = 1000 Watts
For example a system made up of 18 x 370W solar panels = a 6.6 kW system.
When buying a solar power system, its common for installers to quote on oversized systems.
The linked article goes into more detail, but in short you get huge bang for buck by putting on 33% more panels than an inverter is rated for.
This is why 6.6kW solar systems, using 5 kW inverters, are king in 2021 they represent a sizing sweet spot for what the typical home can fit on the roof. Theyre also usually the maximum size a Distributed Network Service Provider will allow on a single-phase home .
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How To Calculate Energy Usage
Calculate how much energy in kwh you use a year and the average monthly total. Note we say average because you probably wont be using 3000 kwh every month.
You might use more power during the summer for the AC, fans, etc. or you might spend more on heaters during the winter. If you own a farm, the energy cost will likely be tied to the needs of your livestock and poultry.
Bottom line is your usage will be less than 3000 kwh in some seasons and higher during others. If you are going for a hybrid or grid tied system, you have to know when your energy consumption is highest so you can offset that with solar power. If your usage goes up to 3200 kwh or more during the summer, you can reduce the cost with a solar array .
Find Out How Many Solar Panels You Need
The easiest way to find out how many solar panels you need is by doing a simple math equation.
If the optimal area of your roof faces south:
If you have a south facing home you can expect your solar panels to produce about 525 kilowatt hours each year. For example, the average home in Scottsdale, Arizona uses 17,500 kilowatt hours per year. In this scenario, you would only need 34 solar panels to cover your 17,500 kilowatts of electricity usage.
How much does a 34 panel solar system cost?
Take your total kilowatt hours and divide that number by 1750.
For example, if we use the 17500 kilowatt hours example, and divide that by 1750, that would equal a 10 kilowatt system and at a cost of $3,200 per kilowatt, that total would equal $32,000.
If the optimal area of your roof is facing east or west:
If you have an east or west facing home you can expect your solar panels to produce about 480 kilowatt hours each year. In this scenario, you would actually need 37 solar panels to cover your 17,500 kilowatts of electricity usage.
How much does a 37 panel solar system cost?
Take your total kilowatt hours and divide that number by 1600.
For example, if we use the 17500 kilowatt hours example again, and divide that by 1600, that would equal a 10.9 kilowatt system and at a cost of $3,200 per kilowatt, that total would equal $35,000 for a 37 panel solar system.
A 10 kilowatt system produces only between 16,800 and 17,500 depending on the direction the optimal part of your roof faces.
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Total Mean Capacity Factor
The total amount of electricity a solar panel generates over the course of a year depends on how much direct sunlight it receives.
This calculator/website, Renewables.ninja, calculates the solar power effectiveness anywhere on the earth, calculated as the total mean capacity factor, which is a combination of how many hours of sunlight and how much cloud cover any given location receives.
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For example, a solar panel on a roof in Nevada has a solar total mean capacity factor of 20.8%. This means that the solar panel can be expected to generate its full power capacity for 20.8% of the year. Whereas the same panel on a roof in Alaska has a total mean capacity factor of 10.1% – generating less than half the amount of electricity as the same panel in Nevada.
Location
You need to make sure that the panels make enough total electricity each day to match the total amount of electricity your home uses during that day. Taking the US average yearly total of 10,649kWh, this works out at 10649kWh / 365 days = 29kWh used per day .
