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How To Size A Residential Solar System

About Solar & Battery System Sizing

How to Size your Solar Power System

Battery storage system sizing is significantly more complicated than sizing a solar-only system. While solar panels generate energy, batteries only store it, so their usability is based first and foremost on the energy available to fill them up . The size of the solar system installed will usually be the primary dictator of the size range of the batteries which can be paired with it, followed by the homes energy consumption levels and usage patterns if a home uses a lot of energy during the day, there will be less solar available to go into the batteries.

In fact, the most important thing to look at is the relationship between the amount of energy that the household consumes on a daily basis and the amount of energy that the solar panel system produces day-to-day.

Solar Panels For Commercial Businesses

For businesses, solar panels might represent an environmental good or a financial strategy.

Whatever the reason could be, solar panels are a great move for all sizes of businesses.

Just as in residential cases, the size dimension of your system will be determined by the same factors listed in the how much power do I need section. And the size of solar panels for commercial businesses are just the same as the ones we mentioned above.

Nonetheless, since businesses require on average more power than homes, the typically used solar panel size in businesses is 72-cells size or more, like that of 96-cells.

The difference lies in the size of the solar panel array, given that the power demand for commercial businesses is higher than for residential use.

The figure below illustrates an approximation of that comparison.

An average home fits its energy needs with systems of around 6 kW or 7 kW. Businesses will require larger systems. In this case, expect to occupy a larger rooftop surface to cover your companys energy needs.

If you install a 6 kW system with, say, 20 average-sized solar panels, expect to occupy a surface of 27 ft. wide by 13 ft. long on your rooftop.

The table below shows a rough idea of the common size of solar panels for commercial businesses and the expected price range

Common system sizes for commercial businesses and expected price range.

System size

How To Properly Size A Battery System

By John Connell, VP of Crown Batterys SLI Products Group

Oversize your solar panels, inverters and batteries and youll waste money. Undersize your system and youll compromise battery life or run out of power particularly on cloudy days. But if you find the Goldilocks zone of ample battery capacity, your solar-plus-storage project will work seamlessly.

By sizing your system using the ROI method Reduce electrical demand Observe power draw and calculate amp-hour requirements and Incorporate a safety buffer you can ensure the best combination of solar and storage will be used to fulfill your energy needs.

Read Also: Can You Get Paid For Solar Energy

How Many Solar Panels Do I Need

The number of solar panels that you need depends on the system size that you select. However, you can have a different number of panels for the same size system. A 5kW solar system can be made up of 20 x 250W panels, or 15 x 333W panels, it all depends on the efficiency of the solar panels you select. The higher the efficiency, the less solar panels you will need.

Buy with confidence

Complete Guide For Solar Power British Columbia 2021

How to size the panels of your solar power system ...

Congratulations! Youve found the ultimate guide for going solar in British Columbia!

British Columbia is currently ranked the #6 province in the country for installing a solar power system, scoring as one of the best provinces for installation costs and utility-related factors.

This page contains all relevant information about installing solar in BC including utility policies, system financing, solar incentives, and natural factors

This guide is sponsored by Empower Energy, a residential and commercial solar developer serving all of British Columbia. to visit their website and to get a free cost estimate.

The guide begins by answering the two most common questions about solar systems, then it explores each solar ranking factor.

You can read from top to bottom, or skip to your preferred section by clicking on it below:

3. System Costs

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How Big Is A Solar Panel

There are many brands of solar panel, and each brand is slightly different in size. However, on average, one standard solar panel will be approximately:

A solar panel is made up of a series of small photovoltaic cells wired together. Most domestic systems use solar panels that have 60 of these cells.

The full system consists of a number of solar panels, typically placed next to one another.

At YES Energy Solutions, we offer two types of solar panel, depending on the system you choose.

  • StandardVikram Eldora Ultima 250W polycrystalline panel 1,640 mm × 992 mm × 40 mm
  • DeluxeSolarWorld 280W monocrystalline panel 1,675 mm × 1,001 mm × 33 mm

Calculate A Solar Energy System Requirement

You need to match the kilowatt hours of your solar PV system to the kilowatt hours that your appliances will use. To approximately estimate the energy requirement for a period of time, we need to multiply the hourly power consumption by the number of hours of intended use. An example for the same would be a 40W appliance in domestic use that will be used for 2 hours per day. The daily energy consumption for it would be 40*2 = 80 Wh.

Repeat that exercise for every appliance individually to calculate the daily energy requirement for your solar energy system. Add in any appliance that will use power while connected to the solar panel. The result will give you an indicative total energy requirement for the solar panel to produce for the day. You can work out the number of panels needed a few ways.

You calculate how many solar panels you may need by dividing the maximum hourly solar energy system output by the wattage output of one single panel. The number of solar panels of the size used in the calculation will theoretically meet that energy demand during a sunny day.

Another way is to multiply the households hourly energy requirement by the peak sunlight hours for the area. Then divide that answer by the wattage of the solar panel intended to be used.

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How To Calculate Solar Panel Size Needed

If you are looking into purchasing solar panels to be installed on your roof, then you are in for a fantastic experience. They are a brilliant way to provide energy for your home and lower your annual energy bills in one go. Plus, they are environmentally friendly and require hardly any maintenance. However, before you buy, it is important to have a rough idea of the panel size and amount that you will need. Make sure you consult a professional and accredited installer about this, but this page can act as a rough guide.

This Post Has 3 Comments

How To Size Your Solar System
  • sandeep benjamin27 Oct 2020Reply

    Hi,i loved your explanation of solar system it was very well explained, but on a personal note can I discuss with you via email i need more advice on this subject.

  • Rachana1 Nov 2020Reply

    This article was very helpful. Thank you very much!In this you have covered on grid and off grid only. I am looking for a mix of these, where I want a solar battery backup during power outage, and the excess generated is sent/exported to the grid. Do we have a possibility of this one?

  • Priyavrat Bhatt8 May 2021Reply

    Thats pretty nice description. Now, I have a house that is yet to be constructed and I dont know my average electricity consumption but I know that I will be running 3-4 fans, for almost all the time in summer, 8 20 watt tube lights for about 4 hrs, 1 geyser for about 2 hr in winters and some 3-4 10-12 watt LED bulbs in lawn for about 3 hrs all through the year. ACs wont be there. And add a 50 inch TV running for say 8 hrs a day apart from charging my laptops, phones etc. how many solar panels I will need with no dependency on government supply?

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    Calculating Your Electricity Consumption

    What you want to look for is kilowatt hours . Add up the kWhs for all 12 months. Divide that number by 12 to get an average. Then, divide the monthly consumption by 12 to arrive at your daily kWh usage.

    To get even more detailed and this is a great opportunity to accurately assess where you could be saving electricity add up the kWhs of anything that uses electricity. Your electric bill doesnt itemize the energy draw of heating, cooling, lights, kitchen appliances, washer/dryers, hair dryers, power tools, computers, and other devices so its great to know how much certain devices use so you can eliminate them or upgrade to more efficient units.

    How do you arrive at kWh energy usage of your appliances and electronics? This is a labor-intensive assessment thats generally not needed for calculating your solar system size but its a great way to audit your homes actual energy needs.

  • Calculate how many watts each device uses every day
  • Convert the watts to kilowatts
  • Multiply the daily kWh by 30 to determine the monthly usage
  • For example:

    • One 20W fluorescent garage light on for 2 hours per day = 40 W/hrs
    • One 50W ceiling fan on for 24 hours per day = 1200 W/hrs or 1.2k Wh
    • One 70W LCD TV on 6 hours per day = 420 W/hrs
    • One 50W laptop on 8 hours per day = 400 W/hrs
    • One 10W Wi-Fi router on 24 hours per day = 240 W/hrs
    • One 200W refrigerator on 24 hours per day = 4800 W/hrs or 4.8 kWh

    How To Choose The Right Residential Solar Panel System

    Before you decide which home solar power system is right for you, you have to consider your available sunlight, required system size, economics, and the local permits youll be required to have.

    First, you have to assess your site to see if it would provide enough solar energy to meet your electricity needs, both economically and efficiently.

    You have to consider the geographic orientation and tilt of your panels as both can affect your Photovoltaic systems performance.

    Next, assess your energy consumption as this would help you become more energy efficient, reduce the size of your PV system, and lower the amount of capital needed in addition to operating costs.

    Lastly, you have to choose between stand-alone off-grid solar systems or one thats grid-connected. Some utility companies will even pay you for unused electricity you put into the grid, so this is also something worth investigating.

    To help you meet your energy needs, the following information will help define the differences between each residential solar power system available on the market.

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    How Many Hours Of Sunlight Can You Expect In Your Area

    The peak sunlight hours for your particular location will have a direct impact on the energy you can expect your home solar system to produce. For example, if you live in Phoenix you can expect to have a greater number of peak sunlight hours than if you lived in Seattle. That doesnt mean a Seattle homeowner cant go solar it just means the homeowner would need more panels.

    The Renewable Resource Data Center provides sunlight information by state and for major cities.

    Now multiply your hourly usage by 1,000 to convert your hourly power generation need to watts. Divide your average hourly wattage requirement by the number of daily peak sunlight hours for your area. This gives you the amount of energy your panels need to produce every hour. So the average U.S. home in an area that gets five peak sunlight hours per day would need 6,000 watts.

    Calculate The Amount Of Batteries You Need

    Solar Hot Water

    Now that you know how much power you need, you need to figure out how many batteries you need to store it.

    • Do you need only enough storage for a day or two or do you need to have enough batteries to store 3 or 4 days, or more, worth of power?
    • Do you have another power source, like a generator or turbine, that will kick in if the sun doesnt shine?
    • Will you be storing the batteries in a warm room or will they be in a cold location?

    Batteries are rated for storage at around 80 degrees Fahrenheit. The colder the room, the bigger the battery bank you need by over 50% more for below freezing. Each of these answers affects the size, and cost, of your battery bank.

    What voltage battery bank do you need 12V, 24V, or 48V? Generally, the larger the system, the higher voltage battery banks are used to keep the number of parallel strings to a minimum and reduce the amount of current between the battery bank and the inverter. If you are just having a small system, and want to be able to charge your cell phone and power 12V DC appliances in your RV, then a basic 12V battery bank makes sense. But if you need to power much over 2000 watts at a time, youll want to consider 24 volt and 48 volt systems. Besides reducing how many parallel strings of batteries youll have, itll allow you to use thinner and less expensive copper cabling between the batteries and the inverter.

    Use our off-grid calculator to calculate what size battery bank you need based on these answers.

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    What Affects Solar Panel Output Efficiency

    Heres where solar panel quality makes a difference. Not all solar panels are alike. Photovoltaic solar panels come in wattages ranging from about 150 watts to 370 watts per panel, depending on the panel size and efficiency , and on the cell technology.

    For example, solar cells with no grid lines on the front absorb more sunlight than conventional cells and do not suffer from issues such as delamination . The construction of our cells makes them stronger and more resistant to cracking or corrosion. And a microinverter on each panel can optimize power conversion at the source, in contrast to one large inverter mounted on the side of the house.

    Because of these wide variations in quality and efficiency, its difficult to generalize about which solar panels are right for you or how many youll need for your home. The main takeaway is that the more efficient the panels are, the more wattage they can produce, and the fewer you will need on your roof to get the same energy output. Conventional solar panels usually produce about 250 watts per panel, with varying levels of efficiency. In contrast, SunPower panels are known to be the most efficient solar panels on the market.*

    To figure out how many solar panels you need, divide your homes hourly wattage requirement by the solar panels wattage to calculate the total number of panels you need.

    So that average U.S. home in Dallas, Texas, would need about 25 conventional solar panels or 17 SunPower panels.

    Scaling Up With A Micro

    Being modular, a micro-inverter system can have one panel added at a time. However, you would need to consider the cost of getting an installer out to your house every time a panel needed to be installed. There is no need to match new solar panels to existing panels should you wish to install more in the future.

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    Solar & Battery System Sizing Table

    Using Sunwizs PVSell software, weve put together the below table to help shoppers choose the right system size for their needs. PVSell uses 365 days of weather data Please read the paragraphs below and remember that the table is a guide and a starting point only we encourage you to do more research before deciding on a system size.

    Calculating Your Energy Usage

    How to Size a Residential Solar Panel System

    Next, you need to know how much energy your home consumes regularly. This will help you figure out what power output is needed to run your home with solar energy.

    Its actually very easy to determine how much energy you consume. As per the solar energy installers here, the simplest way to do it is by checking your electricity bills for the past year. Add up the years worth of kWh used, then divide by 12 to get an average monthly figure. Divide that by 30 to get a rough estimate of the kWh your household uses daily.

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    Factors Increasing Number Of Solar Panels For Your House:

    Even the most expensive solar panel in the world will not work in its full potential if not installed correctly. The generation of solar panels depend on the following factors:

    If after doing shadow analysis you found that your solar panels will get shadow free light only for 3 hours then you will have to oversize your solar system by adding extra 1 kW of solar panels.

    Solar Insolation And Weather

    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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