What Size Solar Generator Do I Need?

Posted 7 months ago by Kami

This is a question that people often ask, and it can be difficult to answer.

The truth is, there is no one-size-fits-all answer, as the size of the solar generator depends on your specific needs. The size of a solar generator for camping would be much different than if you need a solar powered generator for your RV.

So, instead of just giving you an arbitrary number and hoping it will work for you, in this article, we will show you exactly how to size your own solar generator step by step.

But first, let’s start with the basics of a generator.

How To Read The Specifications Of A Solar Generator

1. Inverter Size (Continuous Power)

This is the maximum amount of power that the solar generator can output consistently at any given time. It is usually expressed in watts (W) or kilowatts (kW).

This number is important because it determines the size of the appliance you can run.

For example, a small appliance like a laptop might require around 60 watts, while an air conditioner could require upwards of 1200 watts.

So, if you only need to power a laptop, you can go with a small 300W generator and you will be more than fine.

But if you need to run the air conditioner, you will need at least a 1200W generator, and if you need to run both the laptop and the air conditioner simultaneously, you need a solar generator that can provide 1260W (1200W+60W).

2. Inverter Peak

It’s often called surge power or peak power and it’s the maximum amount of power that the solar generators can output for a short period of time.

Why is this important?

Well, some appliances, like air conditioners and refrigerators require a quick burst of power to start up, generally 2-7 times their running wattage.

For example, a small freezer might require 1200 watts to start but only use 600 watts once it’s running.

If your generator isn’t able to provide this surge, the appliance won’t start.

This is why it’s important to check the generator’s peak power rating before purchasing.

3. Battery Size

The battery size is usually expressed in amp-hours (Ah) or watt-hours (Wh).

Obviously, this is an extremely important factor, as this will determine how long the solar generator can run at its maximum wattage output before it needs to be recharged.

For example, a generator with a 2000Wh battery can run a 50W refrigerator for more than 40 hours (2000/50) before it needs to be recharged.

As a rule of thumb, the bigger the battery, the longer the run time.

4. Solar Input

Also measured in Watts, this is the maximum amount of power that the solar panels can input into the solar generators.

This number is important because it will determine how fast you can recharge your generator’s battery.

For example, if you have a 3000Wh generator with a 500W solar panel, it will take approximately 6 hours (3000/50) of direct sunlight to fully recharge the battery.

However, if you have a 3000Wh generator with a 1000W solar panel, it will only take approximately half that time or around 3 hours.

Sizing A Solar Generator Step By Step

Now that you understand the basics of a solar generator and what do those weird numbers mean, it’s time to size one for yourslef.

Step One: Start With a List

The first thing you need to do is make a list of all the appliances you wish your generator to power.

Make a table like this one:

ApplianceNumberWattage/ApplianceHoursTotal
LED Lights3
Fan1
Kettle1
Fridge1
Laptop1
Phone Charger2
Make a list of all the appliances you wish your generator to power

Step Two: Determine The Wattage Of Each Appliance

Now that you have a list of all the appliances, it’s time to find out the power consumption of each one of them.

You can find this using one of these methods:

  1. The wattage can usually be found on the appliance’s Energy Guide label. So, go through each appliance and write down the wattage.
  2. Use an online appliance power consumption list. This should give you a rough estimate but keep in mind that it’s not super accurate.
  3. Use a Watt Meter Plug. This is a device that plugs into the wall and the appliance you’re measuring and will tell you exactly how many watts the appliance is using.
ApplianceNumberWattage/ApplianceHoursTotal
LED Lights35W
Fan130W
Kettle11200W
Fridge1600W
Laptop160W
Phone Charger24W
Find out how much power each appliance uses

Step Three: Determine How Many Hours You’ll Use Each Appliance

Now that you know how much power each appliance uses, it’s time to find out how many hours you’ll use each one in a day.

This is important because it will help you determine the battery size you need.

ApplianceNumberWattage/ApplianceHoursTotal
LED Lights35W8 hours
Fan130W8 hours
Kettle11200W0.2 hours (12 minutes)
Fridge1600W8 hours (30% duty cycle)
Laptop160W3 hours
Phone Charger24W2 hours
Find out how many hours per day you’ll use each appliance

Step Four: Multiply The Number Of Appliances By The Wattage And The Hours Used

Now, take the wattage and multiply it by the number of hours used to get the watt-hours (Wh) used.

This will give you a better idea of how much power each appliance uses in a day.

ApplianceNumberWattage/ApplianceHoursTotal
LED Lights35W8 hours120Wh
Fan130W8 hours240Wh
Kettle11200W0.2 hours (12 minutes)240Wh
Fridge1600W8 hours (30% duty cycle)4800Wh
Laptop160W3 hours180Wh
Phone Charger24W2 hours16Wh
Multiply the number of appliances by the wattage and hours

Step Five: Add Up All The Appliances

Now, add up all the watt-hours for each appliance to get the total amount of watt-hours used in a day.

ApplianceNumberWattage/ApplianceHoursTotal
LED Lights35W8 hours120Wh
Fan130W8 hours240Wh
Kettle11200W0.2 hours (12 minutes)240Wh
Fridge1600W8 hours (30% duty cycle)4800Wh
Laptop160W3 hours180Wh
Phone Charger24W2 hours16Wh
5596Wh
Add up the watt-hours of all appliances

Step Six: Divide This Number By The Power Factor (0.85)

The power factor is the ratio of real power to the apparent power of a solar generator.

Without getting into technical details, dividing the total watt-hours by the power factor will give you a more accurate estimate of the size generator you need.

5596 / 0.85 = 6583.5Wh

This means that to power 3 LEDs for 8 hours, a fan for 8 hours, a kettle for 12 minutes, a fridge with a 30% duty cycle, a laptop for 3 hours, and 2 phone chargers for 2 hours, you need a solar generator with at least 6500Wh battery.

Step Seven: Calculate The Generator’s Continuous Power Output

So far, we have calculated the battery capacity, but we also need to take into account the generator’s power output.

As we mentioned earlier, a 300W portable solar generator won’t be able to power a 600W fridge.

For this reason, you need to make sure the continuous power output of the solar generators can handle running all these appliances simultaneously.

To do this, you need to multiply the number of appliances that will run at the same time by their wattages, add them all up, then divide it by the power factor (0.85).

ApplianceNumberWattage/ApplianceOverall Wattage
LED Lights35W15W
Fan130W30W
Kettle11200W1200W
Fridge1600W600W
Laptop160W60W
Phone Charger24W8W
1913W
Find out how much power each appliance uses

Using the same example, to run all of our appliances at the same time, we need 1913W.

This means that the continuous output of the generator must be bigger than 2250W (1913/0.85).

It’s important to mention that those numbers aren’t accurate, here we assumed that we will run all the appliances at once while in reality, you might only run 2 LEDs and 1 phone charger at a time.

Also, the electric kettle alone is responsible for 62% of the wattage, so you can significantly reduce the wattage and the size of generator you need by opting for a solar kettle instead.

Without the kettle, the required wattage to run all the appliances at once would be 713W. Thus, you only need an 840W generator.

You get the idea!

Step Eight: Check The Peak Power

We are almost there.

You need to make sure that the surge power of your solar generator is higher than the peak power of your appliances or you won’t be able to start them.

Step Nine: Check The Solar Panel Wattage

Finally, the last thing you need to do is check the solar panels’ wattage.

You need to make sure that the solar panels can recharge the generator’s battery in a reasonable amount of time or else the solar generator will be useless.

Generally, you should look for solar power systems that can charge your generator within 6 hours. Also, you need to make sure your solar power generator feature parallel charging, which allows you to use and recharge the generator at the same time.

Last Words

As you can see, sizing a solar generator is not that difficult once you understand the basics.

All you need is to make a list of appliances and start crunching some simple numbers.

Of course, if you need help or have any questions, feel free to leave a comment below and I’ll be more than happy to help.

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Kami

A passionate solar energy engineer and environmentalist who loves to create content.