How To size the Battery Backup for a Refrigerator

A few days ago I was asked by a former student how to size the battery backup for a refrigerator. My answer was that you need to consider two things before purchasing the battery.

The two things you need to consider when buying the battery backup for your refrigerator are the amount of power the refrigerator consumes while it is working and the amount of power needed to start the refrigerator, I am going to explain this below.

How To size the Battery Backup for a Refrigerator

How much power does a refrigerator use?

The first thing you need to figure out is how much power does your refrigerator consumes, you can find this by checking the power consumption label on your refrigerator. 

Most refrigerator manufacturers have the power consumption rating data for their products. Depending on where your refrigerator was manufactured the power unit can be different, just make sure you convert them to the units that a familiar to you.

The power consumption units can be listed in BTUs (British Thermal Unit) per hour, average WH (watt-hours), or KWH (kilowatt-hours).

Common household refrigerators are labeled to consume between 250watts and 300 watts, but the real power consumption can be even lower, this is because the refrigerator works on cycles, it can work 30% of the time and be Off 70% of the time (this number can be changed depending fast do you want it to cool things).

How much is the start-up power?

Refrigerators contain compressors/motors that will help for air circulations, and these motors will require a high start-up power in order to overcome the inertia when they are completely stopped.

The startup amps are usually referred to as the LRA (Locked Rotor Amps). The locked rotor amps is the amount of power/amperage it takes to start the compressor/motor of the fridge from being completely stopped.

This power is usually 5 to 10 times the nominal power of the refrigerator, this is the reason why sometimes people buy a battery with enough power to run the refrigerator but yet the refrigerator will never start.

For example: if you had a refrigerator that according to the manufacture can consume 300 watts, you will need a battery with an output of 1500 – 3000 watts. If the battery surge watts output is not high enough, it will never get the motor started and not be able to run the refrigerator once the power is lost.

Final words

That is it, this is how you can size the battery backup for the refrigerator, you need to consider the nominal power your refrigerator will consume and also the power surge needed to power the refrigerator when it is not working. 

The failure to do that will result in you buying a battery and finding out that it can not power your refrigerator.

Off Grid PV Without Batteries-Can you do it?

Do you want to go solar, but you are far from the grid lines and you do not have a budget for the batteries, can you have off-grid PV without batteries? 

In this post, I am going to answer the question and give you my advice if do you want to go off-grid without batteries.

Off Grid PV Without Batteries

What is off-grid?

When we say a solar panel system is off-grid it means that it is not connected to any other sources of electricity rather than the solar panels themselves.

The main reason people want to go off-grid without batteries

For me the main reason to want an off-grid system without batteries is to save some money, solar batteries will contribute between 40% to 50% of all your solar installation budget, so removing them will save you a lot of money.

How do the off-grid with batteries work?

This is how the off-grid with batteries work, the solar panels will produce electricity, to be used in your house and at the same time charge the batteries, when there is cloud or at night you will use the energy that was stored in the batteries, the batteries are designed to support all your needs for the whole night.

Can the off-grid solar systems work without batteries?

There is no simple answer to this, for me it depends on what was the intentions of installing solar panels, if all you want is electricity only during the day, yes it can work.

But if you want to use electricity during 24 hours and cloudy days, you can not do it without batteries, you will have to invest in them.

Advantages of installing off-grid PV without batteries

Even though I do not recommend installing an off-grid solar panels system without batteries, there are some advantages to it here are some of them.

Advantages of installing a solar panel system without battery backup include:

  • Savings on electricity bills
  • Less costly to install
  • More environmentally friendly
  • Fewer components to maintain

Disadvantages of going off-grid without batteries

For me, as I stated above, a major disadvantage is that it will not provide power during cloudy days or at night. An installation with battery backup includes batteries that allow electricity to be stored for later use.

Final words

To summarize all this, yes you can go off-grid without batteries, but you will only use solar energy during the day, you can not use it at night or during cloudy days. If do you want to go full off-grid you need those batteries.

You can buy them cheaply from amazon and you will get them the next day.

Can You Use Car Batteries For Solar Power Storage?

I get this question a lot, why I can not use car batteries for solar power storage? Although car batteries and solar batteries are similar, they aren’t the same. Each battery type has a different purpose. In this article, I am going to explain why you can not use car batteries for solar power storage.

Can You Use Car Batteries For Solar Power Storage?

Why do car batteries seem to be an attractive idea?

There are two reasons why most people opt for car batteries for solar storage.

You can find them everywhere

The first reason many people go for car batteries is that you can find them anywhere, you do not have to look harder to see them, you can find them in most local hardware stores. 

They are cheaper

Another reason that people go for car batteries is that they are cheaper, people who are interested in DIY projects tend to reduce cost, for them car batteries are the better option.

The difference between solar batteries and car batteries

As I said above, car and solar batteries are similar but are not the same, each battery type was designed for a specific purpose in mind.

Starting a car engine needs a spike of energy, and the car battery was designed for that, it will provide the spike of energy to start the engine, and while you are driving the car it will be charging. This will not meet the need for a solar-powered home.

Solar batteries are deep cycle batteries, which means the battery can discharge over long periods until it has almost nothing left to give, and then it recharges for further use. Two types of deep cycle batteries are used most for solar. 

What batteries I should use for my solar panel?

After saying all that for me the best battery for your solar panels is the sealed lead-acid battery with these advantages: These batteries are spill-proof and non-hazardous.

Can I recondition a car battery to use it for solar?


The simple answer is no, in theory, this seems to be a great idea for a DIY project, but remember car batteries can not provide storage for a long time and they discharge too fast, you do not either of the two in your project.

Final words

So we have seen that it is not practical to use car batteries for solar power storage, my recommendation is that invest a little bit more in the deep cycle solar batteries and you will be glad you did it.

You can purchase a cheap solar energy battery at amazon and get it at your home in just a few hours.