Calculate Solar Panel Output: How to do it?

With the increasing need for energy and decreasing deposits of fossil fuels, we are looking for alternative energy sources to keep our civilization going. To our knowledge, the already existing substitutes are solar energy, wind energy, nuclear energy, geothermal energy, and many more renewable energy sources.

If you just only think of solar energy, the earth gets 173,000 terawatts of energy from the sun each day, and it is 10,000 times more than the total power consumed by our entire civilization.

Today with the most efficient solar panels, we can only use up to 46% of the sunlight falling on them, which comes down to 15-20% in commercial solar panels. 

So, it is important to know how much power your solar panels are giving back. The more electricity your panels can produce by absorbing sunlight is more beneficial for you. And in that case, you can say your solar panels have greater efficiency.

So, you can see for yourself that solar panel power output is an important attribute to know about. This blog intends to help you gather information about Solar panel power output and how you can calculate it. 

Let’s start from the basics.

What is Solar panel power output?

The amount of electricity your solar panel produces multiplied by the circuit’s voltage is what you can say Solar panel power output. We can remark on the efficiency of your solar panels with the help of this measurement.

A solar panel’s power output is measured in watts, and generally, solar at home has a power output of somewhere between 225 to 350 watts. Your solar panels can produce more electricity if their wattage is high. 

The maximum power output of the panels is known as peak D.C. output. 

How much energy does it produce? 

The output of your solar panels is measured in terms of energy. The total output of your panels is given by the multiplication of panel wattage with the total number of installed panels.

Typical home solar produces about the energy of 1.2 kW-hour to standard 3 kW-hour energy. Some houses have a stand-alone 4kWp system as well. It mostly depends on your living area.

Not all areas receive equal amounts of sunlight, and some areas like Texas or Arizona receive much more hours of sunlight during the day.

If you live in any of these places, you will get sunlight for a maximum time, and your system will be capable of producing a good amount of energy. 

Generally, if your electricity bills are pretty high, a 3kW system can fulfill your requirements sufficiently. 

To give a specific answer to the question, we can observe that our solar panel energy production is not always the same for all, and it’s variable and depends on other factors.

How to calculate?

Well, this looks pretty stressful to calculate how much energy your solar system is producing throughout the day. It seems more complicated if you are unfamiliar with the terminologies and working principles.

But here I’m telling you that you can easily calculate the amount of energy produced by your solar. Don’t stress! 

You’ll get your answer if you multiply the wattage by the number of sunlight hours. Yes! How much energy your system produces is given by the wattage multiplied by sunlight hours. 

I can break this meaning with an even more straightforward calculation. Think of a house getting 5 hours of sunlight in a day. If the wattage of solar panels is 290, the house will get (5×290) or 1450 watt-hour or 1.45 kW-hour of electricity in a day. 

So, you can choose your solar panels according to your energy needs. All houses don’t need high energy. Again some homes don’t get sunlight for a long time in a day.

To get the best fit for yourself, you need to consider how many hours you get proper sunlight at your place and what your energy needs are. You need to do simple math and choose the best for you.

Factors that affect solar panel output

Solar panel output is not solely dependent on the panels themselves, and more dynamic factors are out there. The solar irradiance, the angle of your solar panels, rooftop type, shape, and other geophysical factors impact your solar panel output as well. 

1. Roof design:

Do you have your solar panels installed on the roof? Then the slope and the position of your roof will play a role in how much sunlight is hitting the panels.

As Solar irradiance can make a huge difference in your panel output, we want our panels to get maximum sunlight.

2. Panel design:

Almost every solar panel has a protective layer of glass over the cells. Sunlight passes through it and reaches P.V. cells. So the less light reflected by the glass is the best for us. Also, the angle of the light falling through the glass determines the final amount of generated energy. 

3. Position of panels:

We must install our panels at a place that gets the maximum sunlight all through the day. The panels’ angle also helps capture a significant amount of rays. 

4. Shade:

As solar panels are connected electrically, a small shaded area on one panel can abruptly reduce the whole system’s eventual power output. It’s best to have no shades on the way to get the desired output.

5. Ambient temperature:

Temperature can leave a great mark on your solar panel output. Your panels tend to lose efficiency at high temperatures, reducing power output. However, some panels are manufactured to sustain high temperatures.

These are for warmer or even extreme climate areas, and the panel efficiency doesn’t get harmed by rising temperatures in that case. So, choose your solar panels wisely to rejoice the best out of them. 

Instruments to calculate Solar panel output

Choosing the right instrument gives you the perfect measurement of your solar panel output. With accurate results, it will be easier for you to understand your panel output and to choose the right thing for your solar panels. 

The output of your solar panels is not fixed for all time, and it varies with the varying sunlight and other geographical conditions. Throughout the day, no place gets equal amounts of sunlight.

Your P.V. panels should be able to work correctly under these varying conditions. To measure the output of your solar system, you need a multimeter that can measure the voltage and current in the circuit.

Elsewhere you can use separate devices to measure the voltage or the current. You can use voltmeters to measure voltage and an ammeter to measure the current in the circuit. Then just the simple ohm’s law helps you determine your solar panels’ power output.

Let’s talk about it from the basics. The output power of any circuit is given by the multiplication of voltage and current— ohm’s law.

But one thing to note, the power output depends on the load resistance connected externally with the panels, as the law describes the relation of the current through a resistor with the voltage across it. 

The graphical representation of I-V characteristics of Solar panels can help us understand this relationship in detail.

From this graph, we can see that the power output is zero for an open-circuit and a short-circuit condition. It means when the load resistance is zero, the circuit works as short-circuited, and the power output of your panels is also zero.

The same thing happens with the infinite load resistance, and the circuit behaves as an open circuit, resulting in zero power output.

You can understand from the maximum power dissipation theorem that your panels will give out the maximum power when the load resistance is exactly equal to the array’s or panels’ internal resistance.

The point (specific values of voltage and current in the circuit) at which your solar panels produce maximum power is the maximum power point or MPP. 

How many solar panels are needed to cover up monthly consumption?

Well, this depends on how much your monthly consumption is. If your power needs are high, solar panels with 300 watts or more are the best fit for you. And if you don’t need such power to run your house, you can choose solar panels accordingly. Solar panels with 220 to 280 wattage can also be used for lower energy consumption. 

Now you must be wondering how many of them are needed! This calculation may be pushing you back from getting a solar power system as it seems overwhelming at first. 

But it’s not, and I can assure you that it’s easy to understand and takes a little time of yours. 

To be specific, most homeowners Install multiple solar panels. That’s why we call it a solar panel system, and you’ll be needing several panels too. 

A traditional 3 to 4-bedroom house needs around 3-4kWh energy to run effortlessly. This energy typically requires 10 to 15 solar panels, depending on the panel wattage. 

For example, if you need 3.5 kWh of energy to run your home and install solar panels with 350 wattages. Then you’ll need ten panels to meet up to your requirements.

Some best solar panels with high wattage are produced by the company SunPower or L.G. The Maxeon 3 or X-Series X22 solar panels of SunPower can provide you nearly 400W to 370W power over an hour. Other solar panels provide a higher wattage, i.e., high energy output. 

As I said earlier, a 3-4 kW solar power system is enough for a small family of 3-5 people. Systems with lower output are not recommended for them, and a 1 or 2 kW powering system is good for 1 or 2 persons. 

However, a 3kW system provides a standard output and is mostly used. 

Let’s find out more about the system that can provide a 3kW-hour power output. 

A 3kW system cost

The average cost of a solar is $2.8 per watt, which means for a 3kW system, the cost becomes $8,400 on average. However, this cost varies from state to state. The cost of a 3kW system lies between $6,200 to $11,000. 

Well, location and other factors can also affect the cost. For example, your installation needs. If you have anything specific to care about while installing the system, it will cost more. 

How much energy does a 3kW system produce

By now, you will understand that the energy produced by your system, most importantly, depends on the amount of sunlight it’s getting. If we install a system capable of delivering 3 kW-hours of energy, it is not necessary that the house needs all of it. The energy produced by the system is related to the consumer’s needs. 

If we look at the stats all over the U.S. and take an average, you see the average U.S. home consumes about 800 kW-hours of energy per month. But again, this is variable due to different factors. The monthly consumption of energy of a household can be as low as 270 kW-hours and also high as 1500 kW-hours.

How to measure practical vs. mentioned output?

Some people think if they purchase solar panels with a wattage of 100W, it will give 100W output simply. But the case is not always this exact. The mentioned output is not what we always get.

As we learned, solar panel power output depends on various factors practically; we get somewhat less power from time to time. The practical power output can be directly measured by measuring the voltage and current.

We have good devices to measure that. But also, you can determine the output power by the maximum power point tracking. We can install a maximum power point tracker in our system. It tracks the point at which your panels deliver the maximum power.

This gives you a set of optimum data throughout the day. You can easily see if the power output is the same as mentioned or differs from it. 

How to compare efficiency?

The efficiency of your solar panels is given by the power output divided by the total area of the panels. It is measured under Standard Test Condition (STC) when the cell temperature is 25°C, air mass of 1.5, and solar irradiance is 1000W per square meters area. 

Solar panel efficiency in percentage is given by: 

Efficiency = [ Maximum Power /(Total panel area×1000W/m²) ]×100 

(At STC) 

Panels with advanced ‘Interdigitated back contact’ or IBC cells are the most efficient. Among other types of heterojunction (HJT) cells, half-cut, shingled cells are also efficient. The least efficient solar panels, maybe 60 cell poly or multi-crystalline panels, are also the cheapest. 

The overall efficiency of your solar panels depends on some active factors like irradiance, temperature, cell type, etc. The efficiency of a solar panel matters because an efficient panel is not always better in quality. Also, if your solar panels have a large area, it is not necessarily highly effective. 

One should compare real-world performance, cost, and manufacturer’s warranty in the first place before purchasing solar panels.