When you buy the solar battery storage system, you can generate electricity directly from sunlight. The system gives you grid independence cutting your energy bills.

If you are here, you are probably wondering how much power can your roof solar panel system generate…

In this article, we will take you to discover the secrets on your roof. By the end, you will have a deeper knowledge of your solar battery storage system. Let’s begin!

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Solar Power Variables

There are various ways to calculate how much solar power can be generated by solar panels. Some of the most critical factors in calculating your solar panel’s output include:

  • Your solar panels’ efficiency
  • Your roof’s available square footage
  • Location – how much sunlight shines on your solar panels
  • Which direction your solar panels are facing

Even though there are many variables, these are the main contributors to estimate the power generated.

Standard Test Conditions

The first thing we need to know is the parameters that earn a solar panel its wattage rating. Generally, one solar panel can produce 250 watts to 370 watts. 

Does this mean that your roof solar panel system can generate that exact amount all of the time? It depends from those variables that we mentioned before.

A solar panel’s efficiency number measures how many watts the panel can produce under ideal conditions. These ideal conditions are set during solar panel testing in the laboratory (Standard Test Conditions STC).

In other words, the STC for the solar panel is operating at 77 degrees Fahrenheit and 1000 watts of sunlight per square meter, hitting the panel simultaneously. As a result, under ideal conditions, 250 watts solar panels can produce 250 watts of electricity.

The STC is a helpful way to ensure every solar panel can meet its specific criteria during the manufacturing process.

Solar Panel Efficiency

What do we mean by solar panel efficiency? 

As we mentioned above, wattage can tell you what your solar panel can produce under ideal conditions. On the other hand, efficiency can tell you how much sunlight your solar panel can convert into electricity.

If your solar panel’s efficiency rate is 30%, it means the panel can convert 30% of total sunlight hitting on it. Solar panel efficiency can also be positively or negatively affected by different variables. An example can be the variation of the reflective cell in the panel. High reflective cells can collect less sunlight for later uses.

Here are the common environmental factors that can influence efficiency:

  • Excessive cloud coverage
  • Nearby trees or buildings’ shade
  • Excessive dirt, dust, and pollution
  • Thick layers of snow

Cloud coverage doesn’t mean there is no sunlight hitting the solar panel, but it will dramatically reduce the amount. Shading should be avoided by trimming trees when positioning the solar battery storage system. Dirt, dust, and pollution will degrade the efficiency of the solar panel over time. 

Location & Direction

The location of your home is a critical factor that can affect your solar panel output. More access to the sun will bring more power to your solar panel. If your solar panel is placed in a direction that can barely receive sunlight, the performance of your solar panel will be negatively affected.

General Solar Power Output Equation

Here is a simple formula for calculating the power output of solar panels.

Solar panel watts x average hours of sunlight x 75% = daily watt-hours

Example: If you have a 280-watt solar panel and live in a place where you can get 6 hours of sunlight per day. What are the daily watt-hours for your solar panel?

280 watts x 6 hours x 0.75 = 1260 daily watt hours

Cost vs. Value

The price of a residential solar system usually depends on the total power output of the solar panels. Price in the solar market is typically measured dollars per watt. Higher efficient solar panels will cost more than low efficient panels. This will bring customers a question: Is it worth buying a small and less expensive solar system and still drawing some electricity from the grid?

The upfront cost difference is justified by how much electricity can be generated over the lifecycle of your solar system. 


nRuiT is a consolidated reality for residential solar energy battery storage systems. As one of the leading companies in this emerging industry, we provide a comprehensive range of battery energy storage solutions. 

The advantages of our solar battery storage system are energy conservation, high efficiency, and remote monitoring. Using our solar system can provide complete control over the energy flow and reduce the electricity costs simultaneously.

If you have any questions, please contact us for further information.