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How Much Energy Does a Solar Panel Produce?

How Much Energy Does a Solar Panel Produce

Everything under the sun requires a positive return on investment, especially solar panels.

Yes, it’s an environmentally friendly and sustainable solution in comparison to alternatives.

But how much energy does a solar panel produce and is it possible for prospective owners to estimate, calculate, and rebate energetic expenses, time included?

One panel at a time, we’re here to help keep solar simple, as always. 

Key Terms 

Before we dive into exactly how much energy a solar panel can produce, we need to go back to school for a bit and cover some important terminology. Don’t worry, there’s no quiz at the end.

how much power does a solar panel produce

Watt (W): Watts are the unit of measurement for the amount of energy in an electric circuit equal to one volt at a current of one ampere.

Kilowatt-hour (kWh): A measure of electrical energy equivalent to the power consumption of one thousand watts for one hour.


Key determining factors that contribute to the success of solar solutions include the solar panel rating, efficiency, type and technology, solar cells, overall panel size, and the amount of sunlight available for conversion.

Solar Panel Rating

Solar panels are not rated or created equal, but the individual power rating is always be stated in watts.

Ratings vary according to the model, make, and quality of manufacture.

A solar panel’s rated output’ or peak rating refers to the maximum energy measured in watts that the solar panel can produce under standard test conditions.

These standard test conditions are a cell temperature of 25°C (77°F).

Therefore, the watts are a representation of the panel’s theoretical power production under ideal conditions. It’s an estimate of the panel’s potential, rather than an accurate real-life figure. Nevertheless, higher watts mean more energy.

But watts are not the sole indicator of a panel’s performance.

Let’s explore efficiency.

Solar Panel Efficiency

Solar panel efficiency is measured as the percentage of the sun’s energy that’s converted into electricity, usually between 15% and 20%.

More efficient solar panels translate into more energy.

This means you need fewer panels on your roof to get the same amount of energy as a larger but less efficient panel.

Other factors that influence solar panel efficiency include maintenance and solar panel age.

One of the simplest ways to improve solar panel efficiency is to keep it clean. Any buildup on your solar panel’s surface such as leaves or snow decreases efficiency.

Solar panel efficiency also gradually decreases over time until the panel eventually needs to be replaced. The average lifespan of a solar panel is estimated to be between 25 and 30 years.

Solar Panel Type

Monocrystalline solar panels have higher efficiency at a higher price. They perform better at both higher temperatures and in shadier conditions.

Polycrystalline solar panels are less efficient but more affordable. Currently, they are still less efficient at higher temperatures. 

Solar Cells

Solar panels consist of a series of solar cells. These photovoltaic cells are responsible for the conversion of sunlight into electricity.

Solar cell quality, quantity and technology are largely what determines the degree of solar panel efficiency and the amount of energy produced.

More cells in your panel output more power into the circuit.

Home solar systems are mostly 60-cell solar panels, while larger commercial projects may have 72-cells per panel.

Solar Panel Size

Should two panels be equally efficient, bigger tends to be better.

A larger solar system naturally produces more electricity as a result of the bigger surface area exposed to sunlight. 

how much electricity does a solar panel produce

Therefore, some solar panels have a higher power output due to their larger size, rather than a higher efficiency as a result of more advanced technology.

The Amount of Sunlight

The amount of sunlight is ultimately the core of energy available for conversion.


Sun Hour: The measure of access to solar radiation

Peak Sun Hour: 1 hour of 1000 watts of solar energy per square foot

1 peak sun hour = 1000 W/f2

The number of sun hours per day is a little trickier to estimate as it varies according to your location.

Thankfully, it’s easy to find information on your location online with a little bit of Googling.


Environmental Factors

Geographic location, generalized climate and weather conditions throughout the seasons all contribute to variations in the average amount of sun hours.

A solar battery could be seen as an investment to help you to save and store excess electricity for darker days or other-worldly adventures.

Solar Panel Setup

While the intensity and duration of direct sunlight cannot be controlled, there are ways to optimize sun hours with solar panel setup. 

Solar Panel Position

The position influences the number of sun hours and degree of shading. To optimize solar power production, consider the direction and slope of the roof on which the solar panel is to be installed.

Roof Orientation

A solar panel installed on a south-facing roof will receive the optimum amount of sunlight.

Roof Angle

While the roof angle has less of an impact than the direction, it still affects the amount of direct sunlight.

Ideally, your solar panel should be installed on a south-facing roof at a tilt angle between 30 and 45 degrees.

Why? Solar panels are more efficient when the sun’s rays are perpendicular to their surface. Therefore, the best azimuth angle for the panel would be parallel to the degree of latitude for the specific location.

Estimates and Examples

Most standardized residential solar panels are rated to produce between 250 and 400 Watts per hour, depending on the panel size and efficiency.

The capacity of most residential solar panel systems ranges between 1000-4000 watts or 1kW-4kW per day.

Number of Solar Cells and Energy Produced

Home: 60-Cell Solar Panels: 250-330 Watts

Commercial: 72-Cell Solar Panels: 350-400 Watts

Solar Panel Size

Standard size residential solar panel dimensions: Approximately 66 x 39 inches or 5.5 x 3.25ft

Commercial: Approximately 77 x 39 inches or 6.42 x 3.25 ft

Average Electrical Usage in the U.S

Based on a 1.5% annual increase in electricity consumption, the average electrical usage per U.S home for 2021 could be estimated as follows:

Per hour: 1.24kWh                            

Per day: 29.78kWh                                       

Per month: 906,31kWh          

Per year: 10 875,73kWh                            

Application: Formulas and Calculations

Why try to apply? The two main reasons for attempting these more or less mathematical measures are:

  1. To work out the dollars per watt ($/W) and
  2. To establish if the desired energy target can be achieved.

The three options to go about calculating solar panel output are to use an online calculator, do it yourself, or to get professional assistance.

how many kwh does a solar panel produce per day

An average between the first two should give you a fair estimate before making that final commitment where professional assistance could optimize energetic potential.

Online calculators are readily available, so let’s cast some light on DIY calculations.

First Seek and Find:

  • The number of sun hours for your location
  • The watts per selected solar panel, or
  • The size and efficiency of your solar panel

Some Basic Formulas:

Watts (W) = volts x amps

Watt (W) or Kilowatt-hours (kWh) = number of sunlight hours x power rating of the panel

Efficiency % = power rating in watts divided by surface area x 100

Surface area in m2 = length x width

Complex Calculations Made Simple

Finally. To measure the treasure.

Please bear in mind the potential amount of energy as per solar panel rating is an estimate under ideal set standards.

Per day:

W = Average sun hours x solar panel power wattage

For kilowatt-hours (kWh), simply divide this figure by 1000


Sun hours per day x solar panel size in square meters (m2) x rate of efficiency (in percentage as a decimal, eg 20% = 0.2)

Multiple Panel Solar System:

W = sun hours x the number of solar panels x solar panel rating in watts


16 Panels rated 400W, with 5 sun hours to soak up.

W = 5 hrs x 16 panels x 400W

W = 32 000 or 32kW per day

So with some careful planning, optimization and storage, it’s possible for a solar system to produce enough energy to power the average household.

Per month:

Daily figure x 30

Per Annum:

Daily figure x 3651/4 


The amount of energy varies according to everything under, and between the sun and your solar panel.

But estimated solar panel peak ratings are not to be underestimated. It should be optimized. Saved. And shared responsibly.

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