How To Calculate Solar Needs

And Finally Lets Do Out The Math

We have our three main assumptions now how do those numbers translate to an estimated number of solar panels for your home? The formula looks like this:

Number of panels = system size / production ratio / panel wattage

Plugging our numbers in from above, we get:

Number of panels = 10,649 kW / 1.3 or 1.6 / 320 W

which gives us between 20 and 25 panels in a solar array, depending on which production ratio we use . 25 panels each at 320 W results in a total system size of 8 kW, which is right around the average for EnergySage shoppers looking for a solar installer. Tada!

Why Is Knowing The Amps Important

Amps are, essentially, the amount of power that a device consumes. Amps are really a calculation of the wattage and voltage, but we wont go too much into that since most devices will just list the amperage .

When a device lists an AH, it means amperage per hour. So, if something is 10AH, then it is going to require 10 amps of power per hour to run. So, if you are running it for 10-hours, you need 100-amps.

We are sure that you can see by now just how important knowing how many amps that a solar panel produces is. It is all about knowing whether you are going to be able to power everything inside of your vehicle or not.

How Much Can 250 Watts of Solar Run? > > Check out the video below:

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Determine The Daily Sunlight Average In Your State

As weve mentioned, the amount of sun hitting your roof can determine how many panels you could need. To ballpark this figure, find the average daily peak sunlight hours in your state. We used North Carolina, POWERHOME SOLARs headquarters, for our example.

North Carolina receives an average of 4.71 hours of daily peak sunlight.

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The Climate Of The Area And Peak Sunlight Hours Calculation

The sunlight hours available to your location will directly impact the watts generated from the solar set up.

The more hours of sunlight available the less number of panels required to generate a given output.

Inversely, with lesser sunlight hours, more solar panels will be required. By dividing this average hourly wattage requirement by the number of sunlight hours daily at the location, you calculate the watts your panels need to produce every hour. Using this figure you can select the panels required. The sunlight hours and sun angles vary by season. This will also be a factor for calculating the number of available sunlight hours and thus the panels required.

Lets look at a simple calculation to understand this concept better.

Lets say the summer season sunlight at the location is available for 6 hours and for mid winter it is 4 hours. Then in mid winter a 10w panel will provide 10w * 4h = 40watt-hours of DC power into your battery. In summer the amount would be 10w*6= 60watt-hours. There would be a little energy lost due to resistance through the regulators, cables, and batteries chosen. In calculating the solar power system you would built some assumption of loss into the final calculation.

How Much Energy Can A Solar Panel Produce

How much energy can a solar panel produce While answering that question will depend upon what you need the energy for .

The amount of energy that a solar panel can produce will vary depending upon how it is made. If you need an answer for how much energy can solar panels produce, then you will have to find out which particular solar cells are best suited to your needs.

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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.

Solar Power For Different System Sizes

In our previous calculations, the 8 kWh solar panel system came out to be the ideal condition. However, production ratios differ. Production ratios depend directly on the amount of sunlight a place receives. It flickers between 1.3 to 1.6 depending on the city you live in, in the UK.

The table below displays various solar panel systems, and the production ratio used is 1.6. Since we live in times of high consumption, 1.6 is ideal. 350 watt is taken as the perfect panel wattage in the table.

It is essential to calculate the energy consumption of individual products to estimate the correct solar panel size. Also, a specifically designed roof will alter the size of the system. Considering an average household in the UK, the measure used is 65 by 39 inches or 5.4 feet by 3.25 feet.

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How To Calculate The Right Sized Solar Inverter For Your System

Your home is unlike any other. And so is your energy use. That means when it comes to finding the right sized inverter for your rooftop solar energy system, understanding those energy use patterns is important.

What is a Solar InverterYour solar energy system is made up of several components. There are your solar panels, of course, and they collect the suns rays for you. Those rays arent ready to be used by your home just yet though. Theyre passed through the solar inverter to convert it into energy your home can use.

Solar Inverter SizingWhen considering which inverter to get for your system, you need to understand your homes energy use. How much your home uses on a daily basis will tell you what size inverter youll need to make the best use of your solar energy systemas well as the size of your solar panel installation. Solar inverters come in a variety of sizes, and theyre rated just like solar panels are, in watts. Since your inverter will be converting the DC electricity coming from your solar panels, it will need to be able to handle that amount of wattage. A good rule is that your inverter should be in line with the wattage of your solar system. So for a 5kW system, you can expect the inverter to handle about 5000 W.

Putting It All Together

With those variables in mind, we can roughly estimate the number of solar panels for home that you’ll need. In this example, we’ll use the average annual energy consumption, solar panel wattage and hours of sunlight that we mentioned earlier.

Let’s say that your property receives four hours of sunshine each day, and you’re purchasing 325-watt solar panels. In that case, each panel can generate 1,300 watt-hours per day . Assuming that your energy usage is in line with the average of 29 kWh per day, you’d need 23 325-watt panels to create enough electricity for your home.

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Calculating The Size Of Your Solar Pv System

Now you know how much power you typically use and the times of day you use it. What capacity will your solar PV system need to be to cover your power usage?

First, we’re assuming you’ll have a grid-connected system. This is by far the most common type and it simply means you have solar panels generating electricity during the day, and a grid connection to supply electricity when the solar panels aren’t generating enough . See grid-connected vs off-grid for more.

How much electricity can you expect per kW of solar panels?

Solar PV systems are rated in watts or kilowatts . You’ll see systems described as 4kW, 5kW, 10kW and so on.

1kW of solar panels = 4kWh of electricity produced per day .

For each kW of solar panels, you can expect about 4kWh per day of electricity generation. So a 6.6kW solar system will generate about 26.4kWh on a good day .

It’s just a general rule the actual amount of electricity generated per kW of solar panels depends on your location, the time of year and the amount of sunlight you’re getting, the quality of the system, the orientation of the panels, how old they are, and so on. In southern regions such as Hobart it could be as low as 3.5kWh per day, while the same 1kW of panels in Darwin could generate 5kWh.

Pv System Design Tools

At SolarEdge, weve developed a web-based Designer tool for our installers to plan, build, and validate PV systems, taking all of the above-mentioned parameters into consideration. Location, climate, and other factors are used to design a 3D simulation of the roof that assists in creating a PV layout, complete with electrical design, production simulation, and everything needed to help future PV system owners understand and envision a solar-powered home.

Using Designer, your installer will be able to use your annual consumption figure and your energy consumption profile to give you figures for how much of the electricity generated by your PV system they would expect you to use and export back to the grid and estimate how much you would import from the grid.

Thinking of Including Battery Storage?

When your installer calculates your system size and type, they can take into account both solar PV production and storage. Having an inverter with DC coupling allows you to store excess energy from your PV system. If you are wondering if this is right for you, your PV installer can also simulate this for you in Designer.

To learn more about how much solar energy you need for your home, contact your local SolarEdge-certified installer.

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How Much Do Solar Panels Weigh

If youre planning on installing a rooftop solar system, understanding the weight of your solar panels is another key factor to consider. Knowing a solar panels weight is the best way to be certain that your roof can support a full installation.

While panel weights vary from brand to brand, most panels weigh about 40 pounds.

SunPower panels are the lightest of all major brands*, with some of our panels weighing as little as 33 pounds. For comparison, at the top end of the range some conventional panels weigh as much as 50 pounds.

Series Or Parallel Connection For Batteries

Why Batteries in Parallel, not in Series?

Because this is a 12V inverter System, so if we connect these batteries in series instead of parallel, then the rating of batteries become V1 + V2 = 12V + 12V = 24V while the current rating would be same i.e.100Ah.

Good to Know

Thats why we will connect the batteries in parallel, because the Voltage of batteries remains same, while its Ah rating will be increased. i.e. the system would become = 12V and 100Ah +100Ah = 200Ah.

Good to Know

We will now connect 2 batteries in parallel

i.e. 2 12V, 100Ah batteries will be connected in Parallel

= 12V, 100Ah + 100Ah = 12V, 200 Ah

Good to Know

Now the Required Charging Current for these two batteries.

200Ah x = 20A

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Physical Size Of Solar Panels

A 5kW solar system may produce enough energy to power your home, but you may not have enough roof space for a system of that size. Solar panels for households typically come in the standard dimensions of 1.70m x 1.00m, thats around 1.7m2 for every panel installed. However, the wattage output of the panels will likely vary between 250W and 360W for a more efficient module.

As a guide, youll need 4 x 250W panels, or 3 x 330W for every 1kW of your solar system. If youre considering a 5kW system, thats between 15 and 20 solar panels that will require anywhere between 25.5 34m2 of roof space.

Calculate Area Needed To Install Solar Panels:

On an average the size of all the solar panels which are more than 300 watt is 2m x 1m which corresponds to an area of 2 sq.m or 21.50 sq.ft.

To calculate your total rooftop area requirement to install solar panels use the following equation.

Area required for solar panels = Total number of solar panels x area of one panel

In our above example for a 7.8 kW system we needed 24 solar panels which will need an area of,

Area for 7.8 kW of solar panels = 24 x 21.50 = 516 sq.ft

Mind you this is just the area required to mount all the solar panels back to back and side to side to each other. In real life you need to leave spaces between rows and columns of solar panels so that you can easily clean your solar panels every now and then, and also have safe access to perform any trouble shooting and maintenance.

Considering cleaning space and access for troubleshooting and maintenance of solar panels we can assume to install 1 kW of solar system on a metal roof you will need 85 sq.ft of shadow free areaand to install 1 kW of solar system on a RCC terrace you will need 100 sq.ft of shadow free area.

The following table summarizes the area needed to install solar system.

The values on the left in the area column indicates the bare minimum area required to install solar panels and the values on the right indicates the minimum area required to install solar panels .

Cost of solar panels:

Cost Of Solar On Grid System:

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

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.

Your Current Energy Consumption

Many solar customers desire a system that generates equal to or close to the amount of energy theyre consuming each month. To get a feel for your current energy consumption, look at your watt usage over the last 12 months. Depending on your situation, you may need more or less solar panels to potentially reduce your bill.

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How Many Solar Panels Do You Need For 1000 Kwh Per Month

A family with several siblings can easily reach a monthly consumption of 1,000 kWh. In places with expensive electricity, this results in monthly electric bills of over $200. However, solar power is an effective solution to reduce energy expenses.

As explained above, the number of panels needed to reach 1,000 kWh per month changes depending on local sunshine and panel wattage. To simplify calculations, solar radiation is specified in peak sun-hours per day. Weather scientists calculate this value by measuring the total sunshine in a location and converting it to equivalent hours of peak sunshine.

• Peak sun hours should not be confused with daylight hours
• Since sunlight is moderate in the early morning and late afternoon, these hours do not count as complete peak sun hours
• You may find a site that gets 12 hours of average daylight, and 6 peak sun hours per day

There are many online databases that provide peak sun hours based on site coordinates, including the Atmospheric Science Data Center from NASA. Once you know the peak sun hours, estimating the number of solar panels needed for 1,000 kWh is simple.

• The first step is calculating the kilowatts needed. You must simply divide the average daily kWh by the peak sun hours
• Assuming a 30-day month, an electricity generation of 1,000 kWh is equivalent to 33.33 kWh per day
• If the site gets 6 peak sun hours per day, you need 5.56 kilowatts

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