Saturday, September 16, 2023

How To Size My Solar System

Is 10 Kw Enough To Run A House

How To Size Your Solar System

Yes, a 10kW solar panel system will cover the average American households energy usage of about 10,715 kWh of electricity per year. However, your homes energy needs could be quite different than the average American household. 10kW solar systems do produce enough electricity that you could go off-grid.

How Much Sunlight Do You Receive

Generally speaking, the peak hours of sunlight are between 9am and 3pm each day, although there can be variations depending on your location. Some areas will have more light than others, and there can be a bit of a difference between the north and south of the United Kingdom.

However, this does not mean that you wont have less energy production if you live in a shadier area, it just means that you might need more panels in order to fully benefit. What you can do for a rough estimate is divide you daily kWh usage by the number of peak sunlight hours in a day. This will leave you with the amount of energy you need to produce in kWh. You can multiply this number by 1000 for the watt usage. Of course, you should also consult your installer about this.

How Many Solar Panels Do You Need For Specific System Sizes

In our long example at the beginning of this piece, we determined that an 8 kW system would probably cover the average energy use for an American household if you live in an area with a production ratio of 1.6, which might be a realistic number for homes in most parts of California. Lets extend that a little further, and look at a few more examples. In the table below, weve compiled some solar panel estimates for common system sizes seen on the EnergySage Marketplace. Again, the big caveat here is that were using 1.6 as the production ratio of choice. For California shoppers, this might actually be realistic, but for folks in the Northeast or areas with less sun, these estimates might be a bit high on the production end and low on the number of panels needed.

How many solar panels do I need for my house? System size comparison

System size
44 22,400 kWh

The table above assumes that youre using a 320 solar panel again. However, the number of panels you need to power your home and the amount of space that your system will take up on your roof will change if youre using lower-efficiency panels or high-efficiency panels . Below is a table that will give you a sense of how much space your system will take up on your roof, depending on the power output of the solar panels you select.

How many solar panels can I fit on my roof? System size compared to square footage

System size
711 627

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What About Snow Cover & Shading

We rarely have the ideal location for solar panels steep slopes, perfectly south facing, no shading, no snow in winter etc. The previous section showed how to calculate solar energy yield for locations across the world, and for all different orientations and tilt-angles. What it did not explain yet is how to deal with snow cover in winter, and shading. Unless you have a death-wish and plan to climb on the roof in winter to sweep the snow off the panels, snow cover is something we need to take into account for almost all locations in Canada!

First, let us take a step back and think for a moment about those annual energy yield numbers we have been calculating. In actual life every year will see a different amount of sunshine, and those numbers are an approximation, an average. They are not accurate to three decimal places, what they are is a pretty good idea of what to expect from solar PV for your particular location and case. The way we deal with snow cover should be seen in that light. We are just trying to improve our estimate, and get a better approximation:

For panels that are mounted at a tilt-angle of 40 degrees or more we expect snow to slide off pretty well in winter, and no correction is needed.

For panels that are mounted at a tilt-angle of 30 degrees or less we expect them to be covered in snow for part of the winter. So how do we account for that?

Corrected energy yield with snow cover = PV-Watts estimated yield Half the December yield January yield

What Is A Kilowatt

Solar system size comparison

First, a kilowatt is 1,000 watts. If youve ever changed a lightbulb youre familiar with watts. Most household bulbs range from 25-watts to 100-watts. The more watts, the brighter the bulb and the more electricity used. Watts is simply a measure of power.

Kilowatt-hours is a measure of energy used. If you turn on a 100-watt lightbulb for 10 hours, it would rack up 1kWh of energy. When it comes to your electric bill, kWh is a measurement of how much energy your home or business used in the previous month. If you look at a past bill, youll see that your final cost is a calculation based on how many kWh you racked up.

Solar panel systems use these same fundamental measurements of power supply and energy usage.

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The Duration Of Backup Power/storage Capacity

Once you have a general idea of how much you want to spend on batteries, we can start getting into the technical stuff. First off – how long would you like your batteries to provide power . The longer youd like your system to operate, the more batteries you will need.

Keep in mind how much space you have available to house the batteries. The more storage capacity you need and the more batteries you have, the larger the storage space will have to be. Depending on which type of battery you go with, they will either have to be stored inside or outside. If outside, they should be stored in a shaded and temperate area.

How To Calculate The Size Of Your Solar System

One of the more appealing aspects of going solar is the notion that a solar system will automatically replace your entire electric bill. However, having your own energy supply doesnt guarantee that it will generate enough power to cover 100% of your consumption. These calculations may seem complicated, so in this article well explain how to calculate the size of your solar system based on your actual consumption.

Understanding the difference between your electricity needs and the capabilities of your system can prepare you for the reality of post-solar electric bills. Having a personal energy source does not mean that it is an unlimited supply of energy, but having the right system size and understanding your energy consumption can help you take steps to optimize your systems efficiency.

A solar system is sized according to your past 12-month energy consumption plus the solar capacity of your home.

The offset is calculated on an annual basis . If you divide your total yearly solar production by your total yearly consumption, you may not come close to 100% offset depending on the size and efficiency of your system, and the homes location in relation to the sun.

The good news is that photovoltaic systems are becoming more and more efficient, and with a few considerations you may be able to achieve optimal offset.

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Size Calculation Of Your Solar Panel System

After collecting the numbers from your utility bill and energy audit, you should know how much electricity you normally use and the times of day, and what times of the year you use it. Now we can answer the question, What size solar panel system do I need on my house?

Since the most common solar panel setup is a grid-tied/grid-paired system, we will use that configuration for our example. The biggest benefit of a grid paired system is that you have your solar panels generating your daytime use electricity and a connection to the electrical grid for energy supply during the nighttime when solar panels don’t generate enough electricity. During these times, your house will draw electricity from the power grid.

It is possible for you to have a solar system on your roof that will generate enough electricity for your use, both day and night. However, this would require a sufficient battery backup system as part of your solar panel array.

Check out our Solar Battery Bank Calculator and Calculate your Battery Size Here

How Much Actual Electricity Should You Expect Per Kw That Your Solar Panels Produce?In the Solar industry, all things electrical are measured in watts or kilowatts. You will notice that we describe systems as 5 kW,10 kW, or 20 kW. A kilowatt is not the same as a kilowatt-hour. A kilowatt is how we describe the size of a photovoltaic system – and a kilowatt-hour is the measurement we use to describe the amount of electricity you are using at a particular time.

Length Of Wire & Solar Inverter Performance

How to Size My Off-Grid Solar System & How Much Does it Cost?

One of the factors that can affect your inverter’s performance is the distance between your solar panel array and your battery bank. The longer the wire used here, the lower your inverter’s voltage should be to perform optimally, because with long wires voltage drops and current increases.

The higher the voltage and the lower the current, the shorter length wires you can use. With longer wires, you would need to use thicker wires. This is covered in the Solar Wire Types section.

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How To Calculate How Many Solar Panels You Need

The formula we used to estimate the number of solar panels you need to power your home depends on three key factors: annual energy usage, panel wattage, and production ratios. What does that mean exactly? Here are the assumptions we made, and how we did our math:

Annual electricity usage: Your annual electricity usage is the amount of energy and electricity you use in your home over a full year. Measured in kilowatt-hours , this number is influenced by the appliances in your home that use electricity and how often you use them. Refrigerators, air conditioning units, small kitchen appliances, lights, chargers, and more all use electricity. According to the U.S. Energy Information Administration , the average American household uses 10,649 kWh of electricity per year, so well use that number as the ideal solar panel system or solar array size, which would mean you could offset 100 percent of your electricity usage and utility bill with solar panels . If youre interested in getting a more exact number based on your personal energy usage, check last years utility bills to find out how much electricity you used. Once you have that number, feel free to plug it into the equations below.

How To Size A Solar Pv System For Your Home

With climate change threatening the planet and constantly rising electricity prices threatening your pocketbook, theres no better time to make the switch to a solar photovoltaic system. As technology improves, PVs are becoming more affordable and efficient, making them that much more of an attractive option for your homes energy needs.

But before you hire a company to design and install your new solar panel system, its a good idea to do some homework beforehand to determine your homes electricity consumption and PV needs for your area.

Calculate your Homes Electricity Usage

  • Collect your electricity bills for the past year so you can calculate your average monthly electricity usage. Calculating an average is essential because electricity use peaks in the hottest months due to the high air conditioning demand.
  • Add up the kWhs for all 12 months and divide that number by 12 to determine your average monthly energy consumption.
  • Divide the monthly figure by 30 to determine your daily kWh usage.
  • Appliance
    Total: 1440W/hrs

    Determine Insolation

  • Locate a solar insolation table online to determine the insolation, the average number of hours per day that the sun produces peak sunlight , for your area.
  • Find the nearest city to you on the table and write down the average daily figure. To determine specific insolation data for individual days of the year, use NASAs Atmosphere-Ocean Model.
  • Calculate Energy Needs

    Total Number of Solar Panels

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    Factors That Affect Solar Panel Output Efficiency

    All things being equal, the design of the solar panel determines how efficient it is. This, in turn, specifies how well each square foot can convert sunlight into energy.

    For example, gridlines on most panels reduce the active surface area. Therefore, they are not as efficient as those without them. In addition, grid panels are susceptible to peeling, further reducing efficiency.

    Quality plays a role, too. For example, if the construction is subpar and introduces corrosion and cracking, it can also impact the ability of the panel to absorb sunlight.

    But as a rule of thumb, expect residential solar panels to give you between 150 370 watts. This translates to an average solar panels wattage per square foot of 15 watts.

    How Inverters Are Rated

    Planets of the Solar System

    The first way inverters are rated is in Watts .

    1. Continuous watts is the total amount of watts the inverter can support indefinitely. A 2000 watt inverter can power up to 2000 watts continuously. A bigger inverter size could handle more.

    For your inverter to be right for your system, it’s watts rating must be approximately equal to your solar system’s watts rating. This is the correct way to size an inverter.

    Therefore, if your solar system is rated at 2000 watts, you’ll need a solar inverter with about 2000 watts, maybe a little bit more. But not too much more or the efficiency will drop.You can learn more about watts by clicking here to go to the Electrical Fundamentals section of our website.

    If you want to run multiple appliances at the same time and want to make sure your inverter can handle the load, just add up all the Continuous Watt ratings of all the appliances that may be running simultaneously.

    Depending on the total continuous watts you get, you can determine if you’re inverter can handle it. This is also an important part of inverter sizing .

    So if the total continuous watts of all the appliances that may run at the same time is 3000, it’s too much, you’ll have to run less appliances at the same time.

    The second way solar inverters are rated is in Surge Watts.

    For your inverter to be right for your system, it’s surge watts rating must be approximately equal to the potential surge watts of each appliance.

    Also Check: How Much Would It Cost To Get Solar Panels

    How Big Is A 40kw Solar System

    2,200 square feetA 40 kW Solar Kit requires up to 2,200 square feet of space. 40kW or 40 kilowatts is 40,000 watts of DC direct current power. This could produce an estimated 3,000 to 4,000 kilowatt hours of alternating current power per month, assuming at least 5 sun hours per day with the solar array facing South.

    Final Thoughts From Koos Mulder

    To conclude this article, weve reached out to an expert in solar off-grid systems, Koos Mulder. Koos is installing micro-grid systems in remote villages throughout the Philippines for the Shell Foundation.

    According to Koos:

    Microinverters can be a good choice for AC coupled systems thanks to their high efficiency, however, he brought attention to two issues:

    • Safety As the back of a solar panel can be very hot and the more inverters you have the higher the risk of an electric fire
    • Maintenance Although you might not need to perform maintenance for years, when you eventually do, it might be complicated to figure out where the defective micro-inverter is.

    He still favors central hybrids inverters as they are much easier to install, control and ultimately, they are cheaper. They might be slightly less efficient but it is balanced by all the previous advantages.

    In the end, the main trend is now geared towards energy storage at home, with smart inverters and solar batteries: the Energy Storage Systems .

    Electricity consumers will turn into prosumers, to sell their excess electricity to the grid when prices are high.

    By doing this, we could achieve a higher amount of renewable energies in our global electricity production.

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    What Is The Effect Of Solar Panel Size

    If you have a small or unusually shaped roof, solar panel size and numbers are important considerations. With a large usable roof area, perhaps you can sacrifice some efficiency and buy more larger panels to get to your target energy output. But if your usable roof area is limited, or if its partially shaded, being able to use fewer smaller high efficiency panels may be the best way to make the most possible power over the long term, ultimately saving you more money.

    How Many Solar Panels Do You Need To Power Your House

    How to Size your Solar Power System

    Example Sizing solar panel PV systems

    How many solar panels and their power rating would be needed for a fixed solar system to cover the energy consumption of an average U.S. home?

    Lets say the house is in Burns, Oregon USA, with an average electricity consumption per day of 33 kWh.

    Checking the site Global Solar Atlas, we see that the irradiation in this location is 5.83kWh/m2/day.

    Use historical irradiance data to find suns energy in your location

    • Geographic Location: Burns, Oregon, USA
    • Average daily energy consumption: 33kWh/day
    • Irradiation for Burns, Oregon is 5.83kWh/m2 per day

    PV System Losses

    I previously said that system losses can be 23%, but they can also be higher. Ill use 30% as the overall system loss, to make sure I dont underestimate the number of solar panels to cover the homes energy needs.

    With 30% losses in mind, the energy needs are:

    33kWh/day x 1.44 = 47.5 kWh/day load.

    Now to take into account the efficiency of inverter, which is about 96%.

    The power to be supplied to the inverter = 47.5/0.96 = 49.5kWh/day.

    The average daily irradiation is 5.83kWh/m2

    49.5kWh/day of power can be produced by:

    49.5/5.83kWh/m2= 8.5kW or 9kW of solar panels working at 100% capacity rating.

    To find the number of solar panels needed, divide the wattage needed by wattage of each solar panel :

    Number of panels needed = 9kW/300 watts per panel = 30 solar panels.

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