Friday, August 2, 2024

# How To Size Solar Power System

## How Big Is A Solar Panel

How to Size your Solar Power System

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.

## How Long Does It Take For Solar Panels To Pay For Themselves

Solar panel payback period varies according to your location, as the suns energy is stronger in some locations. It also depends on energy consumption and your utility prices.

The example below shows the payback period for an installation in Houston, Tx:

#### Solar Payback Period Calculation For 5kW Solar Power In Houston, Texas

How long before solar pays for itself in Houston, Texas?

• Location: Houston, Tx

## 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!

Don’t Miss: What Is Solar Home System

## Calculate The Cost Of Solar Panels

One standard solar panel produces about 1.24 kWh per day, and costs around 65 to 75 cents per watt. Solar panels from well-known manufacturers run as high as one to two dollars per watt.

Based on your results from the solar panel calculator above, you can multiply your recommended wattage by 65 or 75 cents to get a ballpark cost for all of your solar panels.

## Calculate The Roofs Usable Area And Type Of Panel Required

The roof size available for setting up the solar panel would need to be ascertained in square feet. Orientation plays an important role, especially if the roof size is small or not of a usable geometric shape.

The size available needs to be divided by the size of the solar panel that is going to be used. If the number of panels is too few due to the size of the roof then one needs to look at the wattage output. Possibly each solar panel will be uniform in size so then you’ll select the panel for its efficiency.

There are various kinds of solar panels available but the differentiating factors among them are the size, wattage, and efficiency of the panel.

Panel efficiency is the ability of the panel to convert sunlight into energy and is a key factor of the cell technology. Panel type will need to be taken into account as a factor to calculate a solar energy system output.

Don’t Miss: What Are Solar Panels Good For

Determine the power consumption demands

Calculate the Total Watt hours per day :

This is calculated by measuring the average watt hours consumed by different appliances per day.

Then Calculate the Total Watt hours per day to be output by the Solar modules :

Multiply the Total Watt hours per day by 1.3. This gives the Total power that needs to be supplied by the Solar Panels.

## What Is The Total Kilowatt Hours You Intend To Run These Appliances In 24hrs

Not all appliances need to run constantly. For instance, your lights only get used at night for a few hours, or your fridge only turns on when it needs to regulate the temperature.

If you multiply the total watts on each appliance by the time you will get your kilowatt hours that would need to be provided within a 24hr period.

I.e. Fridge is 200w and runs for 12hrs per day = 2.4kwh

You would need to do this for all appliances and add them up in total at the end.

Again you can use this formulated sheet to record your findings.

Establishing the type of solar system you want

• Do you want to work directly off the solar array and only use what is provided with no storage?
• Do you want to use only solar and not be connected to the grid?
• Are you wanting to produce a portion of what you use currently and the rest grid?
• Do you want to use a generator for just in case there is no sunlight for a few days?
• There are a few options to go, however, we will be working with a hybrid storage system in this example for this seems to be the most popular for households today.

What is a hybrid system? Well, to keep it simple, basically it means that you use both grid and battery storage. Any power that is stored in the batteries is used first thereafter switches over to the utility grid for the rest until there is more energy to be used in the batteries.

Read Also: How Many Batteries For 2kw Solar System

## How Many Watts Do You Currently Use

Look at your electricity bill for average usage. Look for Kilowatt Hours Used or something similar, and then note the length of time represented . If your bill doesnt show kilowatt hours used, look for beginning and ending meter readings and subtract the previous reading from the most recent one.

You want daily and hourly usage for our calculations, so if your bill doesnt show a daily average, just divide the monthly or annual average by 30 or 365 days, respectively, and then divide again by 24 to determine your hourly average electricity usage. Your answer will be in kW.

A small home in a temperate climate might use something like 200 kWh per month, and a larger home in the south where air conditioners account for the largest portion of home energy usage might use 2,000 kWh or more. The average U.S. home uses about 900 kWh per month. So thats 30 kWh per day or 1.25 kWh per hour.

Your average daily energy usage is your target daily average to calculate your solar needs. Thats the number of kilowatt-hours you need your solar system to produce if you want to cover most if not all of your electricity needs.

Its important to note that solar panels dont operate at maximum efficiency 24 hours a day. . Weather conditions, for example, can temporarily reduce your systems efficiency. Therefore, experts recommend adding a 25 percent cushion to your target daily average to ensure you can generate all the clean energy you need.

## Solar Battery Calculation: How To Size The Battery For Solar Street Lights

How to Size Your Solar System

In the course of designing solar led street lights,

just like many,

youd often encounter the problem of accurately sizing the battery.

This is because,

when the battery is undersized, the street light wont be able to sustain for up to 3 rainy or cloudy days.

Also, if the battery is oversized, youd face the problem of sulfation, especially if its a flooded battery bank.

Well, we have decided to completely solve the challenge of accurately sizing your battery.

Weve compiled a detailed breakdown and a step-by-step guide to sizing the battery for your solar-led street light.

Recommended Reading: How To Use Solar Energy At Home

## Consider Lower Winter Output

Due to a shortage of sunshine hours in the winter months, the solar panel output is significantly less. Ideally, you want a solar power system to generate enough electricity to power your heating needs in the depths of winter. We look at the effect of winter generation on your system size decision using the example for a Melbourne property below:

Electricity use:

• Daily electricity = 18kWh
• Daylight use = 7.2kWh

The output of a 5kW system:

• Average daily output = 18kWh
• Winter daily output = 9.0kWh

In this example, a 5kW system will produce enough electricity in winter to power the daylight usage of 7.2kWh. A smaller system would not be able to generate enough electricity to power the households daylight energy use in the winter months, and this is another reason why selecting a bigger system size is the best way to go.

## How Many Solar Panels Do I Need To Power My House

Whether interested in installing your own DIY solar power system or or just curious, the first step in calculating the size of a solar panel array to power your home always begins with energy consumption.

These are the things you need to know before sizing your homes solar system:

• What is your homes annual energy consumption in kWh ?
• How much do you pay per kWh of electricity
• Will your system be grid-tied or off-grid
• If off-grid, what type of battery will you use ?
• What size solar panels in watts will you use?
• Inverters will you use a central, string or micro-inverter topology
• What are the PV system losses?
• Read Also: How Long To Pay Off Solar Panels

## 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.

## 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.

Read Also: How To Charge Blavor Solar Power Bank

## What Are The Best Solar Panels For Off

We get this question a lot: is there any difference between the best solar panels for off-grid and grid-tie properties?

There is a bit of nuance to the answer.

The panels themselves can always work regardless of system type. There is no such thing as off-grid panels or grid-tied panels specifically.

However, panels must be paired with other components and sized accurately, especially in off-grid systems.

Historically, off-grid systems have used PWM charge controllers, which required that you match 12V solar panels with a 12V battery bank.

Now, most modern off-grid homes will use an MPPT charge controller, which can adjust the incoming PV voltage to work with almost any solar panel.

However, there are still string sizing considerations based on the panel and charge controller specs. All of the components must be supplied with the appropriate voltage and current. Batteries add another layer of complexity for off-grid systems, since the array must be sized to sufficiently recharge the batteries without overcharging them.

There are also a handful of best solar panels that are designed specifically for off-grid applications:

## How Many Kilowatts Does A Solar Panel Produce

To determine how many solar panels you needed for your household, first you need to know the home’s energy load and set your energy goals. In other words you will calculate the solar energy system’s inputs.

The first way to achieve your energy goal is to conserve electric power by reducing appliance use and using efficient appliances. This factor considers reducing your carbon footprint.

The next goal most people strive for is to attain the investment cost of your solar panel system including setup costs. Also, you can get quotes. The initial expenditure outlay can be forecasted by the solar power price calculator to calculate a solar energy system outputs.

There are a number of online solar energy calculators that direct the reader to get a quote from the sponsor after being shown the value of savings available. Solar calculators are often based on the location and roof area with input of the current electricity costs.

Some solar calculators link into Google maps wherein you select the house roof and the software calculates everything for that location. The solar panel system’s price is calculated by the power price calculator.

To calculate the number of solar panels needed for your solar power system, we use the metrics below. These metrics help you calculate the kilowatts required from your solar panel setup. The metrics are:

Recommended Reading: How Much Does A Solar Power System Cost

## 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.

## Inverter Sizing For A Grid

How To Size Your Solar System

Inverters for grid-tie solar systems are simply sized to take maximum advantage of the solar output. In practice this means the inverter can be undersized to around 85% of the solar PV array size without much penalty in energy production. Even for a perfectly south-facing solar array. Solar panels rarely produce rated output, you will see that happen just a few times a year, usually in early spring when it is still very cold outside, with a clear-blue sky, and the sun already high in the sky at noon. The rest of the time solar panels will produce less, much of the time a great deal less, than their rated output.

For solar arrays that are less-than-ideal, it may be possible to undersize the inverter even more, without a penalty in annual energy production. That is something that needs to be evaluated on a case-by-case basis.

It is important to keep in mind that inverters do not need to be the same size as the solar array. This is an area where potentially some money can be saved so there is a better payback period for the solar system, and resources are better utilized.

For our sample solar system of 9.25 kW of peak-power in solar modules this means:

9.25 x 0.85 = 7.9 kW inverter size is sufficient

Fronius makes a nice 8.2 kW string inverter, that is the next size up, and it would be a great choice for this system!

Read Also: How Much Does A Solar Roof Cost

## Estimate How Many Days Your Solar System Will Be Without Sun

If you don’t know this information off-hand, you can look up the annual average of cloudy days for your area online. This step is crucial in ensuring you’ll have access to your solar energy year-round. A large solar battery bank size will be best utilized in areas with more cloudy days, while a smaller solar battery bank should be sufficient in areas with prevalent sunlight. However, it’s always recommended to size up rather than down.

## So How Does This Compare To The Output Of A Solar Power System

The output of a solar system depends on which way your roof is orientated, and now we are getting into the specifics of maximising the benefit of a solar power installation. The Solaray Team will often advise people to go for a split array. Yes, having the panels facing north is best, however, this creates a rough bell-curve of output where you get a peak generation period during the middle of the day. Are you going to be able to use most of the solar power most of the time if you have an output curve like in the image below?

This is a 5kW system in March, turning on as the sun comes up and turning off again at around 7 pm. As an aside, one of the most important points from this image is the maximum output. A 5kW system almost never gets close to 5kW of output at any one time due to the angle and the orientation of the panels. This system has produced 959W in 15m, so around 3.8kWh in the middle of the day. This could be improved with sun tracking, however, the cost of installing and maintaining an array that follows the sun does not pay for the increase you will get in output. It is much cheaper to just get a few extra panels.

Look at google maps to see what roof sections you can install solar panels on. Anything north of west or east is usable.

Don’t Miss: What Are The Pros And Cons Of Having Solar Panels

## Fast Payback On Additional Kws

The cost of increasing the size of the system to 5kW is only \$657 per kW. If we assume that you receive a feed-in tariff of 11.1c for every kWh you export back to the grid, it will only take 4 years to pay back the extra 2kW this is assuming that all of the additional solar power output is exported back to the grid. If you self-consume the power, it will pay back much faster. You can expect the panels to continue generating solar power for another 20 years.

Popular Articles

Related news