The Complete Guide to Calculating Solar Panel Needs


Solar power is a sustainable and environmentally friendly energy solution that aims to reduce dependence on the electrical grid. While transitioning to solar energy may seem straightforward, calculating the number of solar panels required can be challenging. There are several factors to consider, such as geographic location, home energy usage, and the number of sun’s peak hours. In this comprehensive guide, we will walk you through the process of calculating load wattage, power output, energy usage, backup time, and more to help you make the best choice for your solar panel needs.

Understanding Solar Panels

A solar panel, also known as a photovoltaic cell or PV panel, is a device that converts the sun’s energy into electricity. It is composed of individual solar cells made of silicon, phosphorus, and boron. When sunlight hits the surface of a solar panel, the photons knock out electrons, creating a directional current. This direct current (DC) is then transferred to a power station, where an inverter converts it into alternating current (AC) electricity. Using solar panels and power stations, you can charge electrical appliances both at home and during outdoor adventures when you are away from the electrical grid.

The Benefits of Solar Panels

Solar panels offer numerous benefits for homeowners and outdoor enthusiasts:

  1. Clean & Green Energy: Solar panels do not emit toxic fumes while converting the sun’s energy into electricity, making them a clean and green energy source that reduces your carbon footprint.
  2. Zero Maintenance: Solar panels are easy to clean and maintain. Simply wipe off dust with a soft cloth to improve their efficiency.
  3. Safety: Unlike gas generators, solar panels do not require coal or gas to generate electricity, making them safe for indoor use.
  4. Reduced Electricity Bills: By powering your home appliances with solar panels and a portable power station, you can significantly reduce your electricity bills and save money.
  5. Eco-friendly: Solar panels reduce the emission of greenhouse gases into the atmosphere, making them an environmentally friendly power solution.

Solar Panel Calculation

Calculating the number of solar panels needed for a home is not a one-size-fits-all process. Each home has unique power requirements, which depend on various factors. By considering load wattage, energy usage, solar panel backup time, and efficiency, you can estimate the number of solar panels required.

Solar panels have different output capacities, typically ranging from a few hundred watts to 400 watts per hour. However, several external factors affect the actual output of the panels, such as the number of sunlight hours, location, and panel efficiency. To calculate the daily watt-hours, you can use the following formula:

Daily watt hours = Average hours of sunlight × solar panel watts × panel efficiency

For example, if you live in an area with 4 hours of peak sunlight and your panel has a 200-watt rating, the solar panel output would be:

Daily watt hours = 4 × 200 × 0.85 = 680Wh

This means that a single solar panel with a 200-watt capacity can produce approximately 680 watt-hours of electricity per day, depending on its efficiency.

Load wattage refers to the power requirements of your electrical appliances. To calculate the total load wattage, you need to multiply the power consumed by each device by the number of usage hours per day. This will give you the total kilowatt-hours (kWh) per day for each appliance.

For example, if you run a refrigerator for 6 hours and it consumes 300 watts per hour, the load wattage would be:

Load Wattage = 300 × 6 = 1800 Wh

Repeat this calculation for all your appliances and add them up to determine the total power needed for one day.

To estimate your home’s energy usage, you need to determine the average kilowatt-hour (kWh) consumption. Start by gathering the total kWh usage from your electricity bills and calculate the average monthly kWh by adding 12 months of usage and dividing it by 12. Then, divide the resulting number by 30 to get the daily kWh usage.

Next, note down the peak sun hours you receive in your location, as the amount and intensity of sunlight can vary. Finally, divide the daily kWh by the average sun hours and multiply the result by the panel’s efficiency to estimate the solar system size needed.

The backup time of a solar energy system determines how long it can provide power during outdoor adventures or power outages. It depends on the solar battery size and the charge consumed by the appliances. Battery capacity is usually measured in ampere-hours (AH), with the most common type being 12V batteries that provide 80% efficiency. To calculate the backup time, use the following formula:

Battery Backup Time = (Battery AH × 12V × battery efficiency) ÷ Total power consumption

For example, if you are running an appliance that consumes 100W of energy, the backup time would be:

Battery Backup Time = (100 AH × 12 V × 0.8) ÷ 100 watts = 9.6 hours

This means that with a 100 AH battery capacity solar power system, you can run the appliance for approximately 9.6 hours.

When considering solar panel systems, it’s important to factor in the associated costs. The type of panels you choose, such as monocrystalline or polycrystalline, can affect the overall cost. Additionally, the size, conversion rate, and other features of the solar panels contribute to the total expenses. To determine the cost, you can use a solar panel cost calculator or consult with a solar panel installation company.

The payback period represents the time it takes for a solar panel system to generate enough energy savings to offset the initial investment. To calculate the payback period, divide the total cost of the system by the average yearly energy savings.

For example, if you’ve purchased a solar system for $20,000 and it helps you reduce your electricity bills by $70 per month, the average yearly energy savings would be $70 × 12 = $840. In this case, the payback period would be:

Payback Period = $20,000 ÷ $840 = 24 years

Thus, it would take 24 years for the solar panel system to completely offset the initial investment.

Solar panel efficiency refers to the amount of sunlight a solar panel can convert into usable electricity. It is calculated by dividing the amount of electricity produced by the solar panel by the amount of sunlight that strikes the panel. The efficiency formula is as follows:

Efficiency (%) = [(Pmax ÷ Area) ÷ 1000] × 100%


  • Pmax represents the maximum solar panel power measured in watts.
  • Area refers to the length multiplied by the width of the solar panels, measured in square meters.
  • 1000 is a conversion factor to convert power output per unit area from watts per square meter to percent.

For example, if you have a solar panel with a maximum power output of 200W and a surface area of 1.6 square meters, the efficiency would be:

Efficiency = [(200 W ÷ 1.6 m2) ÷ 1000] × 100% = 12.5%

This means that the solar panel has an efficiency of 12.5%, converting 12.5% of the sunlight that hits the panels into electricity.

Solar panel insolation refers to the amount of solar energy that falls on the surface area within a specific time period. It is measured in kilowatt-hours per square meter per day (kWh/m2/day). To calculate solar panel insolation, use the following formula:

Insolation (kWh/m2/day) = Total solar energy (kWh/m2) ÷ Surface area (m2) × Length of time (day)

For example, if a 1-square-meter surface area receives 5 hours of peak sunlight and 5 kWh of energy in a day, the insolation would be:

Insolation = 5 kWh ÷ 1 m2 × 1 day = 5 kWh/m2/day

Note that the actual insolation can vary depending on factors such as location, atmospheric conditions, and the time of year.

Maintaining Your Solar Panels

To ensure the longevity and efficiency of your solar panels, regular maintenance is essential. Here are some tips to help you maintain your solar panels:

  • Clean your solar panels frequently to remove dust and debris that may block sunlight. Use a soft cloth to wipe the surface gently.
  • Protect your portable power station by covering it when not in use and storing it in a clean, dry location to prevent dust and moisture from damaging internal components.
  • Avoid overloading your portable power station by connecting multiple devices that exceed its rated power output. Check the manufacturer’s specifications before plugging in appliances.
  • Use your portable solar power station regularly to keep the battery in good condition and prevent it from self-discharging.

Choosing the Best Portable Solar Panels

When it comes to portable solar panels, BONJOUR SOLAR MCHC450 Solar Panels offer exceptional performance and convenience.

For further information of BONJOUR SOLAR MCHC450, please follow:

Frequently Asked Questions about Solar Panel Calculation

Reducing energy consumption can help lower your electricity bills and reduce your carbon footprint. Here are a few tips:

  • Draught-proof windows and doors to prevent energy loss.
  • Turn off lights and electrical appliances when not in use.
  • Use your washing machine on a 30-degree cycle instead of higher temperatures.
  • Consider air-drying clothes instead of using a tumble dryer.
  • Invest in a solar power generator to utilize free and renewable solar energy for charging devices.

To calculate the payback time of a solar panel system, divide the total investment by the average yearly energy savings. For example, if you’ve invested $12,000 in a solar system and save $1,200 per year, the payback period would be $12,000 ÷ $1,200 = 10 years.

To calculate the energy production per PV module, use the formula:

Energy (kWh) = Area × Solar panel yield × Annual average solar radiation on panels × Performance Ratio

The performance ratio (PR) is typically a default value of 0.75, but BONJOUR SOLAR Solar Panels can reach up to 0.85 for higher efficiency.

To make the most of BONJOUR SOLAR  Solar Panels, combine them with BONJOUR SOLAR Explorer Portable Power Stations. This combination allows you to store the generated electricity in a lithium-ion battery and keep all your appliances charged. BONJOUR SOLAR MCHC450 Solar Panels, with their monocrystalline solar cells, maximize solar power utilization and help reduce high electricity bills.


Switching to solar energy is a sustainable and cost-effective choice for powering your home and outdoor adventures. By calculating load wattage, energy usage, solar panel backup time, and efficiency, you can determine the number of solar panels needed for your specific requirements. Additionally, maintaining your solar panels and choosing high-quality portable solar panels like BONJOUR SOLAR MCHC450 Solar Panels will ensure optimal performance and durability. Embrace solar power and enjoy the benefits of clean, green energy while reducing your carbon footprint.