How Many Watts Of Solar Panels To Power A House

Solar Panel Tolerance Rating

The power tolerance of a solar panel measures how much electricity the panel can produce in relation to its wattage rating. Some panels have a negative rating, which means they may produce less electricity than the specified wattage at STC. At Paradise Energy, we only use panels with a positive power tolerance, ensuring that wont happen to your panels.

Solar Irradiance To Power Output The Relationship

Solar panel output depends on the suns strength and and changes across the day. Its strongest those few hours either side of noon and weakest in the early morning and evening.

Solar installers talk in terms of average hours sunshine per day and they use this value to estimate the average watt-hours a panel can generate over time.

Peak-sun-hours varies according to geographical location and can be found sites such as which has a database of historical solar data. The image below shows the value of irradiance in kWh/m2/day for Houston, Texas.

How many Wh energy for 400 watt solar panel in Las Vegas?

The daily value is usually known as peak-sun-hours and this number is useful when sizing domestic solar panel power.

How Many 400 Watt Solar Panels To Power A House

Nineteen 400 watt solar panels are needed to power the average house. The average American household uses about 11,000kWh of electrical energy per year. A 400 watt solar panel produces 584kWh per year with irradiance of 4 peak-sun-hours. Dividing 11000kWh by 584kWh results in 19 solar panels

Lets assume a very lean overall PV system loss of 10%:

Number of 400 solar panels = home energy needs/solar system production

Each panel generates annually 584kWh- = 465 = 525.6kWh

Number of 400 watt solar panels to power a home = 11000kWh/525.6kWh = 21 panels

The precise number of solar panels you will need for your home depends on how much energy you use and where you live.

Use the solar calculator below to calculate how many solar panels you would need to power your house:

Don’t Miss: Does Pine Sol Have Ammonia

Solar Panel Size Guide: How Many Solar Panels Do You Need

Green Coast is supported by its readers. We may earn an affiliate commission at no extra cost to you if you buy through a link on this page. Learn more.

The size of a solar panel is a huge determining factor for placement, production and optimization. In our solar panel size guide, we will highlight everything you should know about your solar panel sizing and possible power output.

Forget Single Solar Panelshow Much Energy Will Your Whole System Produce

Knowing how much energy a single solar panel produces is all well and good, but more importantly, how much solar power can your roof generate? Lets do the math below:

Take our example above, where youre getting an average of five hours of direct sunlight per day and using solar panels rated at 290 W. Lets say you install 30 of those premium solar panels on your roofthat nets you a 8,700 watt, or 8.7 kW solar panel system, near the average system size purchased on the EnergySage Marketplace. Multiply the five direct sunlight hours we estimated above by 8.7 kW, and we get approximately 43.5 kWh of electricity produced per day. And for one final conversion, if we multiply 43.5 by 365 days in a year, we get approximately 15,800 kWh of electricity produced in a full calendar year from a rooftop array of 30 premium, 290 W solar panels. Considering the average electricity use per year in the U.S. is around 10,600 kWh, thats probably more than enough to power your home on solar.

This estimate is likely on the high end for most solar shoppers, and likely because of our estimate for the amount of sunlight the system will get . To learn more about average sun hours, check out our blog here, where we take a look at average sunlight per year by location.

Also Check: How To Clean Solar Panels Diy

Solar Panel Output Per Square Meter

The most common domestic solar panel system is 4 kW. And it has 16 panels, each of which is about 1.6 square meters in size. They are rated to generate approximately 265 watts of power .

To calculate the output per square meter, you can use the following formula:

• Number of panels x Capacity of the solar panel system
• Capacity ÷ Total size of a system

Also, you have about two different ways to calculate the power production that you might get from your solar panels at home. They are mainly related to how much power you need and how many square meters of roof space they will account for.

You have two options: easy and rough way accurate and complex way.

Roof Space And Strength For Solar Panels

Each 250-watt solar panel measures 65 by 39 inches and a weight of approximately 40 pounds . The roof of your garden office or main property will need to be up to the task of accommodating the surface area as well as the weight and angling of the panels.

Space on your garden offices roof is likely to limit your off-grid ambitions

Clearly limiting what is powered via any installed solar panels will make solar energy far more viable.

For instance, running just the computer, lighting and router consumes 850 running watts which may be far more realistic as it would require only 4 solar panels spread across the roof of your garden studio.

Recommended Reading: Do Sole Proprietors Need A Dba

Type Of Solar Panel And Efficiency Rating

High-efficiency panels can deliver more watts per square foot, which means you need to purchase fewer of them to reach your electricity generation target. There are three main types of solar panels: monocrystalline, polycrystalline and thin-film. In general, monocrystalline panels are the most efficient solar panels, followed closely by polycrystalline panels. Thin-film panels are the least efficient.

Type Of Solar Panel: Mono Vs Poly Vs Amorphous

Modern solar panels are made from silicon solar cells, which are either monocrystalline or polycrystalline silicon solar cells.

Both are similar in terms of energy output, although panel efficiency is typically slightly higher in monocrystalline solar panels.

Theres also a third, less common type of solar module: amorphous solar panels. They are cheaper, but also produce much less power.

Monocrystalline solar panels

These are the most expensive and efficient panels on the market. The cells contain pure silicon and undergo a complicated process of growing long crystal silicon rods as theyre being constructed. The rods are sliced into nearly translucent wafers and formed into cells.

Polycrystalline solar panels

These panels are comprised of multiple polycrystalline cells. They’re slightly less efficient, but more affordable. The cells are processed differently, giving them the appearance of shattered glass. This product is also cut into very thin slices.

Amorphous solar panels

The cells are not crystals, but rather a thin layer of silicon secured to a base material such as glass or metal. While these panels are the least expensive, they also produce far less electrical power.

Calculate the solar panel power output you need to power your home

Recommended Reading: What Is Fpl Solar Now Program

How Is Solar Panel Output Calculated

The maximum or peak amount of electricity that can be produced by a solar panel is defined by its wattage. Remember this is measured under standard test conditions of 77 degrees F, 1 kW of solar radiation per square meter, and no wind. Youll rarely find these conditions in nature, so expect your solar panels output to be a little less than this peak rating provided by the manufacturer.

Once you know the wattage of your solar panel, you can use the following calculation to work out how much electricity your solar panel can produce in one day:

Solar panels watts x average hours of sunlight = daily watt-hours

This calculation relies on you knowing the number of sunlight hours your panel receives. You can either estimate this or use a solar calculator like the National Renewable Energy Labs solar resource maps. Lets look at some examples:

Your solar panel has a rating of 250 watts, and your home receives six hours of sunshine per day. Multiply 250 x 6, and we can calculate that this panel can produce 1,500 Wh, or 1.5 kWh of electricity per day.

On a cloudy day, solar panels will only generate between 10% and 25% of their normal output. For the same 250-watt panel with six hours of cloudy weather, you may only get 0.15-0.37 kWh of electricity per day.

Upgrade to a 400-watt panel, and with the same amount of sunshine, you would now get 2,400 Wh, or 2.4 kWh of electricity per day. On a cloudy day, the electricity generated may only be 0.24-0.6 kWh per day.

What About A Battery

A storage battery will capture the unused solar power generated during the day, for use at night and on low-sunlight days. Installations that include batteries are increasingly popular. See our case study of the first Australian home to install a Tesla PowerWall battery.

But for most homes, we think a battery doesn’t make economic sense yet. Batteries are still relatively expensive and the payback time will often be longer than the warranty period of the battery. However, it’s likely that battery technology and prices, together with future changes in how the electricity market works, will make batteries a good option for most homes within the next few years.

And remember: for most grid-connected systems, having a battery doesn’t necessarily protect you in the event of a blackout. You may still lose all power to your home, despite having solar panels producing power and a charged battery ready and waiting. This is because grid-connected systems have what’s known as “anti-islanding protection”. During a blackout, the grid and any engineers working on the lines must be protected from “islands” of electricity generation pumping power unexpectedly into the lines.

For most solar PV systems, the simplest way to provide anti-islanding protection is to shut down entirely. So, when it senses a grid blackout, your solar PV system shuts down and you have no household power at all.

Also Check: Should I Set Up A Sole Proprietorship Or Llc

Few Things About Solar Panel Output Efficiency

Solar panel type and quality make a significant difference in terms of solar output and efficiency. Not all solar panels are the same.

For instance, monocrystalline photovoltaic solar panels are known to be the most efficient solar panels on the market, but also the most expensive.

Their two main advantages over the other types of solar panels such as polycrystalline or thin film panels is that 1) they absorb more sunlight than conventional cells and their output efficiency is not affected that much by temperature and 2) they occupy less space. These are an ideal option if you do not have enough roof space for standard panels.

On the other hand, polycrystalline panels are cheaper, they are less efficient and therefore occupy more space, but offer a better return on investment than monocrystalline panels.

Because of these wide differences in quality and efficiency, its up to you to decide which solar panels are right for your home.

The main takeaway is that, the more efficient the panels are, the more power they can produce, and the fewer photovoltaic panels you will need on your roof to get the same energy output as you would get with polycrystalline or thin film solar panels.

Overall, if money is not an issue, monocrystalline panels are the best option.

Number Of Solar Cells And Solar Panel Size

To make things easy, we can divide solar panels into two size groups: 60-cell solar panels and 72-cell solar panels. Usually, 60-cell solar panels are about 5.4 feet tall by 3.25 feet wide and have an output of about 270 to 300 watts. On the other hand, 72-cell solar panels are larger because they have an extra row of cells, and their average output is somewhere between 350 to 400 watts. 72-cell panels are usually used on larger buildings and in commercial solar projects, not on residential homes.

Don’t Miss: How Many Solar Panels Can Power A House

Determine Your Energy Usage

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.

Calculate What Size Generator You Need In 3 Simple Steps

To calculate what size generator you need to power your whole home, follow these 3 steps:

Step 1: List out every appliance you want to power.

Step 2: Determine the starting and running wattage of everything on your list. If you cant find these numbers on the appliance label, you can use this wattage estimation guide as a reference.

Note: Starting wattage refers to the wattage an appliance needs at start-up. Starting wattage is normally 23 times higher than its running wattage, or how many watts an appliance needs to run constantly.

Step 3: Add the wattage together. Then, use this number to guide what size generator you need.

Keep in mind that a DIY wattage estimate is just that: an estimate. To be on the safe side, we recommend using a wattage calculator or, even better, having a professional electrician calculate the exact wattage you need to help you find the right size generator.

If youre up for trying it yourself though, lets look at a couple examples.

Also Check: How Much Power Can I Get From Solar Panels

Typical Energy Requirements For Running A Home Office

Guestimates, as we use here are helpful but be sure to sit down with pen and paper and work everything out carefully as it would be a shame to underpower your office.

Here are wattages for typical equipment, appliances and fittings you are likely to run in your backyard home office:

You can calculate the wattage required by adding up all the wattages from your equipment and appliances. In the example above the total running, wattage will be: 3420 watts.

This is the wattage required if all these items were run continually. However, if you are starting everything up from cold, you will need to consider the startingwattage for your office setup.

This reflects the power needed to overcome resistance in the circuitry of the cold, switched off devices. If everything is to be switched on at once a total starting wattage of 4120 will be required.

Of course, demand will be higher if you are operating a workshop and using power tools like welders, compressors, or circular saws.

Quick note: Dont just add up the wattage, it is always good to consider how you will manage the power you generate. A bit of planning may mean you may get away with using fewer solar panels to power your shed. You may want to space or vary the use of items to bring down the demand for starting wattage. For example not running your coffee maker and printer simultaneously.

Key Points To Keep In Mind

Although the upfront costs of a residential solar system might seem high, there are a few ways to save money on your investment. For instance, the federal government provides a tax credit on new solar installations, and many state and local governments offer rebates or incentive programs. Alternatively, if you can’t afford to purchase your panels, you can choose to rent them .

Figuring out the number of solar panels you need is only part of the equation. Learn more about the benefits and costs of home solar from CNET:

You May Like: How Much Power Does Tesla Solar Roof Generate

Can A Solar Panel Work Without A Battery

A solar panel can work without a battery this is how a grid-tied solar system works. Solar panels supply power to the grid when there is over-production. It is not recommended to power appliances without a battery. If clouds pass over the solar panels reduces output and appliances may not work.

Some home appliances, like fridges, freezers and AC units, dont pull the same current all the time but turn on and off.

When a motor starts, a fridge will pull up to 3 times more current than when running constantly. This extra power may well be too much for the solar panel.

This is why energy storage in the form of deep-cycle lead-acid or lithium phosphate batteries are needed to provided the surge current of compressor motors that cycle on and off.

Solar Energy Boom & Benefits

The United States is the worlds second country that is equipped with the most solar power panels in 2021.

Solar energy in the United States has grown exponentially in the last five years.

Solstice reports that in the second quarter of 2021, the United States powered 13.1 million homes after installing 2.1 gigawatts of solar PV that generated almost 69.1 gigawatts of energy.

It also states that the capacity of solar PV will double in the next five years, which means by 2024, more than 15 gigawatts of solar PV will be installed yearly.

Now, lets look at some other interesting facts.

So, what does it mean for the world when one average American family installs solar PV for a year?

The findings based on EPAs Greenhouse Gas Equivalencies Calculator states that one family going solar would avoid adding approximately 12,500 pounds of carbon dioxide to the atmosphere.

It also means growing 122 seedlings for more than 10 years, not burning over 8,000 pounds of coal, not charging almost 937,683 smartphones, and driving 18,000 miles less.

A whopping 59 percent of Americans say that seeing electricity savings on their bill is the biggest motivation.

Around 58 percent of Americans are happy and satisfied after installing solar panels, and believe that this effort of theirs would help the world make a better place for future generations.

Installing solar power panels also creates more jobs in the market.

It is the fastest-growing job and has around 242,000 solar workers.

Also Check: How Does A Residential Solar System Work