How Many Watts Do I Need For Solar Panels

How To Calculate Other Inverter Power Requirements

The examples assume the inverter is going to run a full 3000 watt load every hour. In that case you do need a 12 x 300W solar array to ensure ample supply..

But you wont need that much solar power if the inverter is not going to carry a full load. In fact many users do not like to use their inverter to the limit.

Imagine you have a 2500 watt load that needs to run for four hours. How many solar panels will you need?

Inverter watt load / solar panel watt output + 10% = solar panel array

In this example we will use a 300 watt solar panel:

2500 / 300 = 8.3

8 x 300 watts = 2400 watts. Add 10% and you get 2640 watts.

Round that figure off to 2700 watts. 9 x 300 = 2700.

A 9 x 300 watt solar array can run a 2500W inverter load, even with energy losses factored in.

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.

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Putting It All Together

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

Lets say that your property receives four hours of sunshine each day, and youre 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, youd need 23 325-watt panels to create enough electricity for your home.

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How Many Solar Panels Do You Need For Specific System Sizes

In our long example at the beginning of this piece, we determined that an 8 kW system would probably cover the average energy use for an American household if you live in an area with a production ratio of 1.6, which might be a realistic number for homes in most parts of California. Lets extend that a little further, and look at a few more examples. In the table below, weve compiled some solar panel estimates for common system sizes seen on the EnergySage Marketplace. Again, the big caveat here is that were using 1.6 as the production ratio of choice. For California shoppers, this might actually be realistic, but for folks in the Northeast or areas with less sun, these estimates might be a bit high on the production end and low on the number of panels needed.

How many solar panels do I need for my house? System size comparison

The table above assumes that youre using a 320 solar panel again. However, the number of panels you need to power your home and the amount of space that your system will take up on your roof will change if youre using lower-efficiency panels or high-efficiency panels . Below is a table that will give you a sense of how much space your system will take up on your roof, depending on the power output of the solar panels you select.

How many solar panels can I fit on my roof? System size compared to square footage

Summary: How Many Panels Do You Need

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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Add A Margin For Error

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?

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The Capacity Of Your Batteries

Another way to know how many panels you need is to look at your battery bank.

Batteries come labeled with an amp/hour rating.

This rating tells you how much energy each one can store when its fully charged.

You can use our solar calculator to know how much energy your applications will drain each day.

Youll want to make sure your total amp/hour storage in your battery bank can handle this load each day .

Your batteries amp/hour will tell you how much energy you have available to be used in powering your appliances.

You can increase your available amp/hours by buying multiple batteries and wiring them in parallel.

As we said before, the current from your solar panels has two elements:

Voltage and Current.

These are measured by volts and amps.

If your battery bank consists of 12 volt batteries wired in parallel, your recharging current will have a voltage at or a little above 12 volts.

Once this voltage is achieved, we can calculate our recharge rate by looking at the amps of our recharging current.

If our batteries have 400 amp/hours of energy when fully charged, it would take a 40 amp current around 10 hours to recharge them fully.

It would take a 5 amp current 80 hours to recharge our battery bank.

Key Points About The Solar

• Solar power is most efficient at producing electricity during daylight hours
• A refrigerator is a baseload appliance
• You will need to generate enough electricity to cover your baseload and peak load requirements
• If you have a backup generator, you may only need solar panels to cover your baseload requirements.

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How Many Solar Panels Will I Need

Here are three examples of different sized systems and how many solar panels they need.

The examples are just to show you what information you would have after using a solar system calculator. To make it more relevant Ive chosen different homes in different areas to demonstrate how some the other variable play a role in calculations. As a result, youll see that values like average sunlight and battery storage temperature may change from one example to the next.

How Much Do Solar Panels Cost On Average

The average cost of a solar panel is around $0.65 to more than $2 per watt for high-end models. That means an average 6 kW system will set you back up to $12,000, depending on the location. This is exclusive of installation costs, which can bump the price up by another $5,000 $10,000.

As a rule of thumb, PV systems in warmer locations are cheaper but require more panels, while the opposite is true with colder climates.

Fortunately, tax credits and incentives can cut solar panel installation costs and provide further savings throughout their lifespan.

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How Long Will A 3000w Inverter Run On Solar Power

A 3000 watt inverter either runs on or off the grid. If it is on the grid, the inverter will keep running as long as there is grid power. An off grid inverter runs as long as there is a power source available.

If your home is tied to the grid, only a power outage can stop it from running. If the solar panels cannot generate the required energy, the system will use grid power.

A 3000 watt off grid inverter can run directly off solar panels , but there are limitations. The inverter can only operate during daylight and if there is enough power to carry the load.

For example, the inverter is carrying a 2400 watt load. There are five sun hours in your area. Theoretically the inverter can run solely on the PV array for five hours.

But this assumes the array generates at least 2400 watts. If the output drops below that, the system will not be able to work properly.

Even if there is sunlight, the panels must still produce enough power to maintain the power load. This is why we recommend installing a large solar array so the system can produce more power.

These problems can also be avoided if you have a battery bank. In fact, all large off grid solar systems should have one.

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.

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Ideal Title Angle For Solar Panels

in winter add 15 degrees to your latitude and subtract 15 degrees from the latitude in the summer to calculate the ideal title angle for your solar panel

Tilt angle is the angle formed between a horizontal plane and the pitch of a solar panel

Or use this calculator to calculate the ideal title angle for your solar panel.

Video Effect of tilt angle on the solar panel output

Do Solar Panels Make Sense For My Home

Some factors, like roof direction, roof shading, the solar inverter you choose, and whether or not youre including a solar battery could also influence the number of panels you need. These factors, however, are hard to quantify on your own.

The best way to determine the ideal location for your home solar power system and how many solar panels you need is by getting quotes from qualified local solar companies. Solar installers will also be able to give you an idea of the upfront costs of solar for your home and what rebates, incentives, and tax credits homeowners in your area qualify for.

In the meantime, using the steps in this article can give you a rough estimate of how many photovoltaic solar panels you need to power your home with clean, renewable energy.

Is going solar worth it where you live?

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Table Average House Size In Square Feet 10 Us States Compared

Historical values for irradiance can be found for your location on sites like GlobalSolarAtlas.info. The average irradiance value for the USA is 5.322 kWh/m2/day, so Ill use that value of peak-sun-hours for our calculation.

How many solar panels how much solar do I need to power an average house in the USA?

Using average US values, you can find the theroretical solar power output by dividing the daily kWh by the irradiance value in daily peak-sun-hours:

Solar power required = 30000 watt-hours/5.3 peak-sun-hours = 5660 watts

If 300 watt solar panels were used, the number of solar panels for the average US house would be:

5660 watts / 300 watts = 18.86 solar panels

However, all solar PV systems have losses of about 23%. This can be taken into account my multiplying the solar power required by 1.4:

Adjusted solar output = 5660 x 1.4 = 7924 watts

Using 300 watt solar panels, the actual number of solar panels needed would be:

7924 watts / 300 watts = 26 solar panels

Size Of Your Home And Available Roof Space

Larger homes tend to consume more electricity, and they generally need more solar panels. However, they also have the extra roof space necessary for larger solar panel installations.

There may be exceptions to this rule for example, a 2,000-square-foot home with new Energy Star appliances may consume less power than a 1,200-square-foot home with older, less-efficient devices. When it comes to installation, solar panels can be placed on many types of surfaces.

However, your roof conditions may limit the number of solar panels your home can handle. For example, if you have a chimney, rooftop air conditioning unit or skylight, youll have to place panels around these fixtures. Similarly, roof areas that are covered by shadows are not suitable for panels.

Also, most top solar companies will not work on asbestos roofs due to the potential health risks for installers.

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Example Is A 4kw Solar System Worth It In Houston Texas

Calculate The Solar Payback For A 4kW Solar System In Houston, Texas

How many years to payback a 4Kw solar system in Houston?

What is the average solar payback period for a 4kW solar power system in Houston, Texas?

• City: Houston, Texas
• Solar system power output:4kW
• Solar installation cost = $10960 26% federal tax credit = $8110
• Irradiance level at Houston, Tx = 1552 Peak Sun Hours
• Power generated by solar panel system = 1552 x 4kw = 6208kWhrs
• Houston home electricity cost = 10.98 cents/kWh
• Yearly savings = solar output x electricity cost = 6208 x 10.98c = $690
• Solar payback time in Houston, Tx= solar cost/annual savings = 8110/690 = 11.75 years

The payback period might well be less than this, down to 9 or 10 years. Professional solar installers will give you accurate estimates based on their historical data, and the irradiance level in your geographic location.

How Big Of A System Do I Need

One way to determine the size of your solar energy system is by calculating how many watts you use per day. You can find this number on your electric bill or by using an online kWh calculator that will take into account everything you plug in, like appliances and electronics. Be aware that the number calculated is an estimate.

The size of your solar system will also depend on how many hours per day the sun shines in your area and where you live geographically . But a good rule of thumb for most places in North America is to calculate about 30 watts per square foot or 100-150 kWh/m² per year.

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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.