Thursday, June 6, 2024

How To Calculate Watts Needed For Solar Panel

Add A Margin For Error

how to calculate solar panel watts for home loads

Now that you know how much youre using you need to consider the maximum you may need in the future. If there are any upgrades or extra electrical items you may buy, add them to your table and include them in the calculations.

Now add 20% to your value to give you some room in case you need to add more later.

x 120 = 3.43kWh

Now you can enter this value into the solar power calculator.

I use this one at altE because it provides information about each part of your solar panel system.

You may also be interested to read:The complete guide to off-grid solar inverters, or What is the difference between off-grid and on-grid solar panels?

Will Solar Affect The Value Of My Home

Yes! Each case is different, but on average homeowners see a rise in home value of $15,000. Beyond that, it can generate 10’s of thousands of dollars in savings in your utility bill over the lifetime of your solar system. However, if you want to lock yourself into 2021âs incentives, you should act now.

The Final Calculation Of The Size Of The Solar Power System Needed

Once the daily power requirement estimation has been done, we need to check those calculations for each season. For instance, say the figure applicable to daily power requirement we arrived at is 240w.

We divide the daily watts required by the number of sunshine hours for the season to get the panel size .

  • 240 watt-hours/ 6 h = 40 Watt panel.

Similarly the calculation for winter daylight hours gives:

  • 240watt-hours / 4h= 60 Watt panel.

Depending on the brand of solar panel that you choose to buy, you will know the size of the solar panel you need. So if your chosen company makes 30 watt panels, then you need two panels connected in series. Note that based on the above calculations, the most satisfactory requirement for all year would be to use the higher number of watts and thus solar panels.

The above factors and metrics will help you in calculating the energy requirements for the solar power system that needs to be set up. There may be a difference in the estimated numbers from the actual watts output delivered. When the system is up and functioning you can adjust it.

Recommended Reading: Do Solar Panels Get Damaged By Hail

How Does Irradiance Affect Solar Panels

Although there are several factors impacting solar panel power output, irradiance or the suns energy, is by far the biggest.

Read about solar panel efficiency on one of my blog posts.

Irradiance is measured in kilowatt-hours per square meter per day or year and varies considerably depending on your geographic location.

Irradiance values in kWh/m2/day are also known as peak-sun-hours and this is used by solar installers to work out how much energy a solar installation can generate.

It can be found from historical data using database lookups on sites like GlobalSolarAtlas. Simply enter your city and note your local peak-sun-hours see image below:

Chicago peak-sun-hours is almost the US average

The table below shows the irradiance values for 5 cities, both in the US and abroad:

Table Irradiance in 5 different locations




Incidentally, the peak-sun-hours for Chicago is about the US average , so Ill use that in my calculations.

Good Data In Good Data Out

How to calculate the number of solar panels required to generate the ...

First, lets debunk some common solar system sizing misconceptions. Using the total square footage of your building is NOT a great way to calculate your solar panel system size needs. Its also not about how many people live in your home. This might give you a ballpark estimate of your energy needs, but when dealing with sizing a solar system, you want to be as precise as possible. Like any calculation, if you put bad data into the equation, you get a bad answer out of it.

Remember what youre trying to do here. Youre trying to figure out how much energy your solar system should be capable of producing on any given day. Whether its generated from dirty fossil fuels or from clean renewable sunshine, energy is measured in kilowatts and youre billed for it based on kilowatt-hours . Because of this, your previous electric bills are actually the best guide for how to properly calculate your solar panel system size requirements. More on this later.

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How Many Solar Panels Do I Need

  • Team Nexamp

As more homes throughout the country consider installing solar panels, one question commonly asked is, how many solar panels do I need?. Well, it depends there are a few factors that go into determining how many solar panels you would need to power your home or business home energy usage, roof or property surface area, orientation of your roof and geographic location. In this piece, well break it down for you.

How much solar energy do I need?

When determining how much solar energy you need your homes average energy usage is the first thing to look at. According to the U.S. Energy Information Administration, in 2019, the average electricity consumption for a U.S. residential utility customer was 10,649 kWh. Thats an average of about 877 kWh per month. To understand your own usage, a good rule of thumb is to look back at your total energy consumption from the last twelve months on your utility bills. Most utility bills provide this information. Divide that number by 12 and you have a great estimate of what youll need your solar panels to generate each month.

Solar Panel Size Chart

One of the biggest concerns customers have is the size of solar panels. However, contrary to popular belief solar panels come in tons of different sizes. The different size variants make it easier to buy a solar panel that is perfect for your property.

The two most common configurations for solar panels are 60 cells and 72 cells. The average size for one cell is 6 inches. A 60 cells solar panel is laid out as a 6 x 10 cells grid. Meanwhile, the 72 cells solar panels are laid out in a 6 x 12 grid.

Following are the dimensions for each of these solar panel configurations choose the one which suits your needs the most.

60-cell solar panel size: 39 x 66 inches

72-cell solar panel size: 39 x 77 inches

Moreover, 60-cells and 72-cells are the most common solar panel configurations, but some manufacturers also sell 96-cells solar panels. The size of 96-cells solar panels is below:

96-cells solar panel size: 41.5 x 62.6 inches

Note: Even though these are the standard sizes of commercial and industrial solar panels, the size may vary from manufacturer to manufacturer.

Cell Configuration

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How Many Solar Panels Do I Need To Power My Home

by Khaled Elsheref | Jul 28, 2021 | Uncategorized |

Did you know that in early 2019, the total number of solar energy system installations in the United States exceeded 2 million?

When people contemplate going solar for the first time, one of the first things they ask is, How many solar panels do I require to power my home?

While this may seem to be an easy question to ask, it is really one of the final responses you will get when determining what kind of solar power system to place on your property. The first thing youll need to figure out is how much energy your house is presently using.

Are you thinking of installing solar panels but dont know how many you would need? Here is how to calculate the number of solar panels needed for your home.

Also Check: How To Clean Solar Panels Diy

How Big Are Portable / Rv Solar Panels

Calculating the KWH Your Solar Panels Produce

The other use case to look at is small panels for mobile/remote use. These are the panels used for RVs, boats, and remote applications like solar-powered streetlights. Unlike traditional 60 and 72-cell panels, which are standardized across the industry, smaller panels come in a wide range of sizes. Tiny 5-watt panels take up less than 1 square foot of space. Picking the right panels for your boat or RV comes down to making the most out of the limited space available to you. Though full-sized panels can certainly work on the road, you often wont have the space to mount them, so most people with RVs or boats need a smaller option. Typically these panels come in standard 12-volt or 24-volt output.

What does the wattage of a solar panel mean?

The battery board is like a generator, the wattage is its power, the common 250w, 240w, 235w boards, and of course the small ones less than 100w. The principle of connecting the battery is like charging the battery, the positive and negative poles of the battery plate and the positive and negative poles of the battery can be aligned and inserted.

Also Check: How Much Power Does A 300 Watt Solar Panel Produce

What Is A Watt In Reference To Solar Panels And Calculating What You Need In Your Solar System

When you are talking about electricity coming from solar panelsthe terminology for a watt and watt hours are thrown around frequently. A wattis explained below as a formula for energy transferred per second, while a watthour is the accumulation of power over a period of time. If you have a 100W lightbulb that runs for one hour it will consume 100Wh.

What Size Solar Panel Do I Need

Solar Panels power generation is commonly given in Watts e.g. 120 Watts. To calculate the energy it can supply the battery with, divide the Watts by the Voltage of the Solar Panel.

120 Watts / 18v = 6.6 Amps

Please note that Solar Panels are not 12v, I repeat Solar Panels are not 12v. Any one who works out the Amps of a solar panels using 12v as the voltage calculation does not understand solar or has been misinformed. All solar panel voltages should be marked in the item description of our website or on the unit itself.

The size of the solar panel required to charge a lithium battery depends on the lithium battery’s capacity.

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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.

Summary: How Many Panels Do You Need

How to Calculate Solar Panel Battery and Inverter?

Knowing the answers to the above questions will give you an idea of the ideal number of panels for your electricity generation needs or at least a realistic range. Next, a professional installer needs to assess your roof architecture, angle to the sun and other factors to see if and how youd be able to physically arrange the right number of panels on your roof to achieve your daily energy production goals.

You should also consider net metering as youre considering how much money youll save and make from your solar system. Net metering is how your utility company credits you for producing excess solar energy when the sun is shining and then lets you draw from those credits when youre using conventional power grid at night, if you dont store your excess solar energy in a battery storage system.

To get started, check out our solar calculator, which can help you figure out how much you might save going solar.

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How To Calculate Panel Wattage

Power output is an important metric for your home or commercial solar panel system. When you buy or install a solar photovoltaic energy system, the price you pay is typically based on the total power output of the solar panels in the system . Solar panel wattage represents a solar panels theoretical power production under ideal sunlight and temperature conditions. Wattage is calculated by multiplying volts x amps where volts represents the amount of force of the electricity and amperes refers to the aggregate amount of energy used. The financial savings you derive from the solar system is a result of the electric energy that it generates over time .

Standard Solar Panel Sizes

Traditional solar panels come in two common configurations: 60-cell and 72-cell. The standard dimensions for each option are:

60-cell panels: 39 x 66 72-cell panels: 39 x 77

These are the standard solar panel sizes for most residential and commercial installations, give or take an inch on either side.

There are other panel size configurations on the market, but they are much less common. For example, Panasonic offers 96-cell panels which measure 41.5 x 62.6.

However, the standard 60-cell and 72-cell panel sizes are by far the most common in the industry.

How Big Is the Average Solar Array?

The average American uses 867 kWh of electricity each month. It would take a 6.5 kW solar array to offset 100% of that usage.

6500W / 285W = 22.8 6500W / 315W = 20.6

6500W / 340W = 19.1 6500W / 375W = 17.3

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.

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Alternatives To Solar Panels

As solar technology has developed more people than ever are now able to enjoy the benefits of free renewable solar energy. So, if you cant fit enough conventional solar panels to your roof, then flexible solar panels and solar roof tiles are alternative options.Flexible solar panels are a lot thinner and lighter than conventional panels which helps to make them much more flexible. This means that anyone living in a home with a roof that might not be able to support the weight of several solar panels doesnt have to rule out renewable solar energy as a way of cutting their energy bills.

Solar roof tiles, or solar shingles, tend to be more expensive than solar panels, dont generate as much energy and arent suitable for all roof types, however, theyre an aesthetically pleasing option that are popular as part of a roof replacement.

Also Check: Does Texas Have A Solar Rebate

Figure Out How Many Solar Panels You Need

How Much Solar Power Do I Need? How to Calculate Your Needs

So, you know the size of the solar system you need to cover your energy usage. Now what? To figure out how many solar panels youll need, take the solar system size and multiply it by 1,000 to convert the size from kilowatts to watts.

Next, take the size of the system in watts and divide it by the wattage of the solar panels you want to install.

Voila! Thats the number of solar panels you will need to power your home.

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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.

Find How Much Energy Solar Panels Produce In Your Area

Now that you know how much electricity your home uses in a month, you need to find the amount of sunlight your area receives. This is usually measured in something called peak sun hours, which is essentially the intensity of sunlight in your area.

You can find the average number of daily peak sun hours for your state here. This number is how much sunlight you receive daily, but we need to know how much you receive monthly. To do this, simply multiply your states daily peak sun hours by 30.

The monthly peak sun hours you get tells you how many kWh of electricity 1 kilowatt of solar panels will produce in your area in one day. So, if your state receives 150 monthly peak sunlight hours, 1 kW of solar will produce 150 kWh of electricity per month.

Not sure about the differences between kW and kWh? Read our guide about kW versus kWh and what they mean.

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