Last updated on October 20th, 2019

If You Get A Solar Generator, How Long Will It Run For?

How long a solar generator runs depends on the battery capacity, how much charge the battery has and how much power the connected appliances draw. You need to calculate how much power your electrical devices need before buying a portable generator.

Determining what your power requirements are tells you the required capacity of the solar power portable power station. Heavy-duty devices require an equally large solar generator while smaller electrical devices like a mobile phone can charge several times over with a small solar power battery.

Read on to understand the capacity of a solar generator and how to calculate how much power you need.

How Long Can a Solar Generator Run?

The expected run time is usually mentioned in the product description of most fuel-powered generators but this is not the case with solar generators. Instead of looking at how long a solar generator runs, product descriptions usually mention its power or the battery capacity.

How long a solar generator can run depends on the capacity of the battery, the battery charge and the load. Like with a fuel-powered generator, the more power the connected appliances draw, the faster the battery charge runs out.

The power of a solar generator is given in watts and its capacity in watt-hours of amp-hours. The higher these figures, the more powerful the generator.

However, a powerful solar generator does not necessarily translate to a long run time because the run time also depends on the load. For example, a 500 watt solar generator can keep an LED light on for 100 hours but that same solar generator can only run a mini refrigerator for 10 hours.

This is why finding the right size generator is very important. If you need the generator for electrical appliances that have high running watts then you need a bigger solar power battery while a small battery is sufficient for light use.

The Difference Between Watt-Hours, Watts, Amp-Hours and Amps

There is a difference between watt-hours and watts and a difference between amp-hours and amps. Do not confuse these terms as describing the same thing.

You need to understand the differences between these terms to understand how much power a solar generator has and whether it meets your electrical needs. Here is a quick explanation of their meaning and differences.

The battery power of a solar generator is given in watts. This is the maximum amount of power that the solar generator can provide at any given time.

So, a 500 watt solar generator can deliver power to electrical devices with a wattage of up to 500 watts. A 500 watt solar generator cannot power an electrical device that has a power requirement above 500 watts.

Battery capacity is given in watt-hours. This is the total amount of energy that the battery can store.

So, a solar generator with 400 watt-hours (Wh) has a total of 400 watts stored energy at full charge. Ignoring specific loads and run time,  the watt-hours is the total amount of energy you can draw from a solar power battery. 

In other words, battery power is the maximum output expressed in watts and the battery capacity is the total amount of stored energy expressed in watt-hours. Think of the watts as the rate of power flowing from the solar power battery to the electrical device and the watt-hours as the maximum total power it can deliver.

The relationship between amp-hours and amps is similar to the relationship between watt-hours and watts. Amp-hours is the total amount of current that solar power battery can deliver and the ampere is the maximum current that flows.

The amp-hours are less informative than watt-hours because you would need to convert the amp-hours to watt-hours to know how much power the battery holds.

How to Calculate How Much Power You Need from a Solar Generator

Now that you know what each term refers to, you can calculate the power of a solar generator using the information provided in the product description.

Here follows how to calculate your electricity requirements and how to calculate how much power a solar generator has.

Calculating Required Power
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  • Make a list of all the electrical devices that you want running on the solar generator. Note down their wattage and how many hours you wish to run them for.
  • If the wattage is not mentioned on the device, calculate the wattage from the given amps using this formula: Watts = amps x volts
  • Calculate the total wattage and the total running hours.
  • Multiply the total wattage by the total running hours. This is the required battery capacity or the watt-hours (Wh) to power your electrical needs.


Factoring in Recharge Time

Certain solar power generators can recharge while the battery is also being used to power electrical devices using a trickle charge. Simultaneously charging while using the solar generator means that a lower capacity battery might still meet your needs.

This is how to factor in the recharge time into the above calculations.

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  • Note down the power rating of the solar panels. Add the power ratings together when using connected solar panels.
  • Compare the total power rating of the solar panels to the maximum trickle charge rate of the battery (you can find this in the manual). The lower rating is the maximum recharge rate.
  • Take the total required battery capacity you calculated before and divide this by the maximum recharge rate. This is the battery recharge time.


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If the battery recharge time is less than the number of hours that you want to keep the generator running for then the trickle charge lets you use the battery longer. If the battery recharge time is longer than the running then your solar battery will still run out of charge.

So, how long a solar generator runs depends on the load. Calculate what your power requirements are to decide how much battery capacity your solar generator needs to run for how long you need it.

Are You Looking For A Solar Generator?

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