James Elston

James Elston

Published July 11, 2024

If you want to charge a 200 Ah battery, you will need a solar panel with a power output of 400 W to 500 W.

This article will cover how to calculate the solar panel size you need, as well as the factors that influence this.

Note: This article focuses on lead-acid and lithium battery capacities.

What Size Solar Panel is Needed to Charge a 200 Ah Battery?

A few factors will influence the size of the solar panel you need to charge a 200 Ah battery. These include the efficiency of the solar panel, the type of battery, and how many good hours of sunlight are available in your location.

Solar panel size calculation

Let’s look at the calculation to determine the size (watts) of the solar panels you would need to install to charge a 200 Ah battery.

  • Formula: (battery capacity) x (voltage) = watt hours (Wh)
  • Example: 200 Ah x 12 V = 2,400 Wh

Next, you will need to incorporate the hours of sunlight you get daily. 

  • Formula: wattage hours (2,400) ÷ sunlight (e.g. 5 hours) = size of solar panel
  • Example: 2,400 ÷ 5 = 480 W

To account for inefficiencies and other external factors, round this number up to the nearest multiple of 50, e.g. 500 W.

Once you have this number, you can also work out how many solar panels you need to charge a 200 Ah battery. 

For example, if you have 250W solar panels, you would need two of these to change a 200 Ah battery. 

Factors that influence the size of solar panels needed to charge 200 Ah battery

While the calculation we provided will give you a good estimate regarding the solar panel size needed, a few factors can influence this number, meaning you may require a larger or smaller system. 

Size of the solar panels

A solar panel system with a lower wattage will take significantly longer to charge a 200 Ah battery than a solar system with a much higher wattage.

Efficiency of the solar panels

The more efficient your solar panels are, the more electricity they can generate. This means that you may require a smaller solar panel if it is more efficient. 

Additionally, regular maintenance and cleaning ensure your solar panel system functions optimally, as dirt and other external factors can impact efficiency. If you need help, our certified solar engineers at Eco Happy are here for you. Contact us today for expert solar panel maintenance and servicing.

Peak sun hours

Depending on how much sunlight your solar power system is exposed to will influence how well and how fast it can charge a 200 Ah battery.

A sufficient amount of sunlight per day is around 4 hours. This will ensure your solar array functions to the best of its abilities.

The UK gets around five hours of sunlight per day, with peak sunlight hours amounting to around 2.5 to 3 hours. So, your solar panel system may take slightly longer to produce sufficient energy to charge a 200 Ah battery. Alternatively, you may need to install more or bigger solar panels to produce enough energy. 

Solar charge controller

Solar controllers control the voltage and current between the solar panel and the battery, ensuring your batteries don’t overcharge. This provides a safe and efficient charging process.

There are two types of solar charge controllers that differ in cost and power:

  1. MPPT (Maximum Power Point Tracking): Expensive and more efficient (quicker charging times).
  2. PWM (Pulse Width Modulation): Cheaper and less efficient (slower charging times).


Grey weather or shading affects your solar panels by limiting the amount of access they get to sunlight. This means you may experience power loss and significantly less electricity energy production.

To help combat this, it’s best to install your solar panels in a location that gets the most sun with the least shading from buildings, trees, etc.


Can a 300 W solar panel charge a 200 Ah battery?

Under ideal circumstances, a 300 W panel can charge a half-depleted 200 Ah battery in around 5 hours (a lead-acid battery can only be drained up to 50%).

What is the minimum charging current for a 200 Ah battery?

A 200 Ah battery should be charged at a minimum charging current of 10 amps. This means that after 20 hours of charging, the battery will be fully charged.

What is the lifespan of a 200 Ah battery?

The lifespan of a 200 Ah will depend on its usage. However, the general lifespan is around two years.

James Elston

James Elston

Boiler Expert

James Elston is the top boiler replacement and heating expert at Eco Happy. He has over 20 years of experience in the industry, focusing on Gas Safe boiler installations and offering home-heating and energy-saving solutions to homeowners across the UK. From sourcing the most energy-efficient combi boiler to providing specialist heating advice, James ensures that Eco Happy maintains the highest standards and best customer service.

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