Sunday, April 14, 2024

How Large Of A Solar System Do I Need

Determine Your Energy Usage

HOME SOLAR SYSTEM INSTALLATION | What Size Solar System Do I Need for My Home? [PART 2]

Check out your most recent power bill to see your monthly electricity consumption. In most cases, the total amount of electricity used will be shown at the bottom of the bill in kilowatt-hours .

Your yearly energy usage will give you the best estimate for how many solar panels you need, as energy usage fluctuates in different seasons .

Because monthly energy usage varies so much, it can be beneficial to dig up your monthly electric bills for the past year, add the electric usage together, and divide by 12.

But using just one utility bill to find your energy consumption is still enough for a ballpark estimate.

How Many Solar Panels Do You Need For Common Household Items

If you are considering solar energy for your home, you may also be asking how many panels are needed to power specific appliances. However, it is important to understand how solar generation works:

  • Solar systems deliver most of their energy production in the hours around noon
  • During the early morning and late in the afternoon, solar generation is much lower. This is because there is less sunlight reaching the panels
  • Households have the highest energy consumption in the evening and early morning

Since solar panels depend on sunlight, you cannot control their electricity production. Powering home appliances directly with panels is impractical and potentially dangerous, unless you use a solar battery to store energy. If you connect home appliances directly to the panels and inverter, a dark cloud passing over your home will shut off the power. At night, you would have to switch to the local power supply anyway.

The most practical solution is synchronizing solar systems with the local power supply, which lets them operate as a single power source. When solar generation cannot power your home appliances by itself, the rest of the energy comes from the grid. If your panels have surplus production, you can send it to grid to get a credit on the next electricity bill.


This table considers the most power-hungry appliances found in homes. Most small appliances and electronic devices have a very low consumption, which does not even match the production of one panel.

So How Many Solar Panels Do You Really Need To Get 1000 Kwh Per Month

If your goal is to produce 1,000 kWh per month, then truly you must produce 1,250 kWh per month to allow for loss in output efficiency.

Remember, if you are receiving an average of four hours of usable sunshine per day and your solar panel is rated at 250 watts of power, then you will need forty panels to reliably generate 1,000 kWh per month.

An average residential solar panel size today is about five and a half feet by three feet.

But the number of panels and consequent space needed can vary depending upon whether you select lower-efficiency economy panels or high-efficiency premium panels.

Consider this table when trying to figure out how many solar panels you can put on your roof:

So go out and take a look at your roof and consider the sunlight falling on it. Think about the size and placement of solar panels. Do a cost analysis of the savings you will experience from creating your own clean, renewable energy.

Read our article about available solar power incentives and rebates that might make financing your savings attractive now.

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How Do Solar Panels Generate Electricity

PV solar panels generate direct current electricity. With DC electricity, electrons flow in one direction around a circuit. This example shows a battery powering a light bulb. The electrons move from the negative side of the battery, through the lamp, and return to the positive side of the battery.

With AC electricity, electrons are pushed and pulled, periodically reversing direction, much like the cylinder of a car’s engine. Generators create AC electricity when a coil of wire is spun next to a magnet. Many different energy sources can “turn the handle” of this generator, such as gas or diesel fuel, hydroelectricity, nuclear, coal, wind, or solar.

AC electricity was chosen for the U.S. electrical power grid, primarily because it is less expensive to transmit over long distances. However, solar panels create DC electricity. How do we get DC electricity into the AC grid? We use an inverter.

Solar Insolation And Weather

Solar System Scope

This factor is extremely location-dependent. If we compare peak sunlight hours – a measurement of the average amount of sunlight a location receives – we see that sunny Tucson, Arizona gets 7.5 – 7.9 PSH. That is more than twice the sunlight that rainy Seattle, Washington gets – which is only 3.3 – 3.9 PSH.

That means that, all things equal, to get the same solar system output in both locations, the system in Seattle will need to be twice the size of that in Tucson!

Any method you choose to calculate solar system size will take your locations peak sun hours into account. PVWatts has access to the National Solar Radiation Database, which has years of solar radiation and meteorological data.

The SolarReviews calculator and your local solar company get access to the same dataset through PVWatts.

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Need Help With Solar System Sizing

Of course, sometimes its easier to talk to an expert who knows how to size a solar system and can walk you through the design process. Once youre ready, we do encourage you to schedule a free design consultation with us so that we can double-check your sizing, find compatible products, and ensure the system works within your constraints .

The fastest way to get a thorough evaluation of your solar needs is to call us at 1-800-472-1142 and connect with one of our designers. Wed love to help you design the perfect grid-tied system to meet your solar requirements.

Determine Your Daily Energy Usage

You’ll want to look to your electric bill for this information. It will usually be printed as your monthly kilowatt-hour output. To calculate your daily kilowatt-hour output, you will need to divide that number by 30, then multiply by 1000 to convert the number into watt-hours. Which translates to one watt of power sustained for one hour. This is the first step in determining your solar battery bank size.

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Roof Orientation Obstructions And Shading

Your solar system is designed for maximum production. As such, we avoid placing panels near obstructions such as trees or other structures that may block the path of the sun. Each solar panel should be exposed to sunlight to produce the most electricity.

In the northern hemisphere, its best to have your panels on a south mounting plane. If a south mounting plane is not available, east and west are also good. Roof planes must be able to accommodate a minimum of two panels to be considered in your final design.

Can A 10kw Solar System Power A Home

How Many Solar Panels Do I Need?

Yes, a 10kW solar panel system will cover the average American households energy usage of about 10,649 kWh of electricity per year.

However, your homes energy needs could be quite different than the average American household. In fact, energy consumption varies a lot between states. Homes in Wyoming and Louisiana, for instance, tend to use more electricity than homes in other states. So while a 10kW solar array might be perfect for a home in Louisiana, it might be too big for a home in a state like New York, which uses much less electricity on average.

10kW solar systems do produce enough electricity that you could go off-grid. The only thing is you would also have to install solar battery storage to store the excess electricity a 10kW off-grid solar system produces.

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How Do Solar Panels Work

When photons hit a solar cell, they knock electrons loose from their atoms. If conductors are attached to the positive and negative sides of a cell, it forms an electrical circuit. When electrons flow through such a circuit, they generate electricity. Multiple cells make up a solar panel, and multiple panels can be wired together to form a solar array. The more panels you can deploy, the more energy you can expect to generate.

What Type Of Solar Panels Should I Install

The choice of solar panel type can be based on efficiency, cost, and available space. Some types of solar panel are more efficient that others, and this would affect the number of panels you need to install.

For example, you need less space to install monocrystalline panels compared to thin film and polycrystalline solar panels.

There are different types of solar panels that can be installed on your roof, but the most commonly installed panels are monocrystalline or polycrystalline solar panels.

  • Lower efficiency rate compared to monocrystalline
  • More sensitive to high temperatures compared to monocrystalline

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What Affects Solar Panel Efficiency

The efficiency of a solar panel is affected by a number of factors, but two of the most prominent are the type of panel it is and how much sunlight it receives.

  • Type of panel: As mentioned, there are three types of solar panels: monocrystalline, polycrystalline and thin-film. Because of the way they’re manufactured, monocrystalline panels are the most efficient.
  • Amount of sunlight: If your home is heavily shaded, your roof orientation isn’t optimal, your panels aren’t facing the best angle or your panels are dirty, they won’t perform as well.

The Number Of Solar Panels You Need Depends Upon You

Solar System Print

You now have a rough idea of the number of solar panels you need to power your home. Great! But still you have to pay attention to a few more details to set up your solar power system for success, including your budget and solar goals. We recommend you engage a solar panel professional to address the following questions about solar panel installations.

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How Do I Calculate The Right Size Solar Array For My Home

To work this one out, you need to ask yourself three questions:

1) How much power does your household use?

2) How big is your roof?

3) What’s your budget?

Number three is the most important consideration. Irrespective of your energy usage and roof size, cost is surely the deciding factor when it comes to choosing a solar PV system.

According to a study by Which?, the average price of a 3.4-4kWp solar PV system is £6,672. To learn more, take a look at our detailed guide to solar panel costs.

If youd like to find out how much solar panels will cost you, simply fill in this short form, and our professional installers will be in touch.

Average System Size And Power Output By Location

We know that real-world output for a given system size is affected by several factors and is constantly fluctuating. But dont worry – its possible to account for weather conditions in your area based on decades of historical data, which allows us to calculate average solar power output for a given solar system size at any specific location.

Average solar system size in selected states


*Daily kWh generation figures can see large variations between seasons, and even from day to day.

Do note that the figures above are just averages. The amount of power generation will vary, especially if weather conditions where you live are different from the state average, or if your roof has a sub-optimal orientation or angle.

Dont worry though, you can still come up with accurate system size and production figures for your specific home – just use one of the three calculations methods we discussed earlier.

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How Much Roof Space Is Needed For Solar Panels

The average solar installation will require between 335 and 405 square feet of roof space. To find out how much roof space your solar system needs, just multiply the number of panels you need by 17.55 square feet, which is the area of most residential solar panels sold today.

If you have limited roof space, you may need to get high-efficiency panels, or panels with a higher power output so you can install fewer panels while still covering your energy needs.

Divide Your Total Watts By The Wattage Output Of One Solar Panel

I Installed a Power Plant Myself | HUGE DIY Solar Panel System

Lastly, we must divide the number of watts of the system by the number of watts one solar panel generates. POWERHOME SOLAR uses premium 320-watt panels, so well use that.

6,500 / 320 = 20.3 Solar Panels

To Recap: If you consume 914 kWh per month in North Carolina, you could need a 6.5 kW solar system to potentially offset 100% of your current electric bill, which is equal to about 20.3 solar panels.

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How Many Solar Panels Do You Need To Power Your House

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.

What Are Peak Sun

Its also important to bear in mind that environmental conditions can affect the amount of energy that your solar panels produce. While a 1kWp solar PV system is expected to produce roughly 850kWh of electricity each year, in reality this figure will vary depending on the number of peak sun-hours your panels experience.

A peak sun-hour is an hour in the day when the intensity of sunlight is at least 1,000 watts per square metre. Naturally, the amount of solar radiation increases each day towards noon, and then decreases again as the sun starts to set. The seasons will also determine how many peak sun-hours there are, with the summer bringing the most, and winter bringing the least.

Here is the average number of daily peak sun-hours in the UK for each month in 2019, as reported by the Department for Business, Energy & Industrial Strategy.

Month of 2019

Once you know how many peak sun-hours you can expect, use this equation to calculate how much electricity your solar panels will generate per day:

Daily peak sun-hours x PV systems rated output x 0.85

Why 0.85? Well, when solar irradiance exceeds 1,000 watts per square metre, solar panels are rarely able to absorb more than about 85%.

So, if you have a 3kWp solar PV system, this would be its expected electricity output in the UK in July:

8.7 x 3 x 0.85 = 22.2kWh per day in July.

Meanwhile, its output in the middle of winter would be much lower:

1.4 x 3 x 0.85 = 3.6kWh per day in December.

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Determining Individual Solar Panel Sizes

To determine the size of the panels that you need for your house, you need to know the following:

  • How much energy do solar panels with different capacities generate?
  • The capacity of your roof: how much space in square meters is available?
  • Dimensions of solar panels per size or brand.
  • Solar panels generate different amounts of energy depending on their wattage size or rating. A 250 watt panel will generate up to 250 watts per sun hour while a 300 watt solar panel can generate up to 300 watts per sun hour. This is why it is important to know the amount of energy you need before determining solar panel sizes.

    In the earlier example with a daily consumption of 4 kWh , if the homeowner used 250 W solar panels, then they would need to install 16 solar panels . If they used 350 W panel, then they would need 12 solar panels .

    The capacity of your roof impacts the number of solar panels you can install and therefore how much energy you can generate. This is also because different solar panel sizes have different dimensions.

    Continuing with the previous example, if you are installing 16 250W solar panels, you would require a surface area of 25.6 m².

    If you are installing 12 350W solar panels would require a surface area of 22.8 m².

    It is therefore important to know how much space you have. The table below outlines the average solar panel dimensions and weight per system size.

    Required Solar Panel Surface Area

    Solar panel size *

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    The latest ACs come with a nameplate having details mentioned, e.g., power consumption, rating, size, etc. That power consumption thing comes in handy when calculating how much power your AC will use approximately annually or in your desired days. OR If you want to figure out your AC power consumption manually, use a Kill A Wattmeter. You have to plug your AC wire into the meter and connect the meter to a socket. It is recommended to study the readings for at least seven days. To calculate how many watts would be used by your AC in a day, multiply the number of hours you want to use by power consumption. To calculate the number of watts for a whole year, multiply the result by 365 days, or if you want to run for summer, four months, then multiply it by 120 days. Not to mention, less power AC starts consuming after constantly cooling for two to three hours, so calculations would be rough, not exact. For the sake of calculations, we assume your AC adds 3000kW to your bill annually, your solar panel system would have to be producing equal or more to offset additional load.

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