How many solar panels does your refrigerator need?

Solar panels can power your refrigerator.

A house is incomplete without a refrigerator.

It is one of the most essential appliances in your home.

Its cooling keeps our food fresh for a longer time.

Most of us keep it ON for 24 hours a day.

This means it consumes a good amount of electricity.

In this post, I’ll discuss the following things:

• The average watt of a refrigerator
• Energy consumption of your refrigerator
• How much does it constitute to the electricity bill
• How to save more on electricity with your refrigerator?/Factors that affect energy consumption
• Top refrigerators in India
• How to size solar panels for your refrigerator
• Finding the solar profitability with your refrigerator
• Things to keep in mind while buying a refrigerator

The average watt of a refrigerator

We have all types of refrigerators such as small, medium and big.

A domestic fridge has somewhere 100 watts to 250 watts of power rating.

In a day, the fridge consumes 1 kWh to 2 kWh of energy.

Let us understand the relation between the terms Power and Energy.

Power is the energy consumed per unit of time (Power = Energy/Time)

Or

Energy = Power x time

Units of Power are watts

Units of time in hours

Hence

We have Energy units as watts-hour (Wh)

Or

kWh

Know the energy consumption of your refrigerator

The power plate of your refrigerator helps in finding its energy consumption.

It is generally located on the lower left side of the fridge.

My refrigerator is 150 watts.

Let us calculate its energy consumption as follows:

Refrigerator power = 150 watts

Usage = 24 hours per day with 33% duty cycle

(The compressor, inside the refrigerator, switches ON and OFF throughout the day. When it notices that the fridge has achieved its desired level of cooling, it gets OFF.

When the temperature rises beyond the set limit, it switches ON and starts the cooling)

On average, it works 1/3 of the time.

I mean 1/3 of 24 hours = 8 hours

Net usage = 8 hours

Therefore, the total energy consumption in a day = 150 watts x 8 hours

= 1200 watt-hours

Or

= 1.2 kWh

(The above usage is just an approximation; it all depends on many factors that I will discuss later in this post).

How much does it constitutes to your electricity bill

The average grid rate in India is Rs. 6.6 per unit.

A high grid rate means you are saving more when you switch to solar.

Which is growing by 8% annually.

However, I am not taking escalation into effect to keep things simple.

My monthly energy consumption for the refrigerator is:

Daily consumption x 30 days x grid rate per unit

= 1.2 kWh x 30 x Rs. 6.6

= Rs. 238 per month

And

In 1 year, it is Rs. 2850

That is when things are ideal like:

Right ventilation, no frequent opening of the doors, properly maintaining the temperature of the freezer and the lower compartment, etc

To get the practical view, add 20% to this ideal consumption.

That is:

1.2 of Rs. 2850

= Rs. 3420 (That would be close to the real annual energy consumption of your refrigerator having 150 watts).

Factors that affect energy consumption of your refrigerator

Not every refrigerator consumes the same energy.

It depends on its type, technology, and size.

In addition, your usage habits also affect the energy consumption of the refrigerator.

Let us discuss each one of them:

a) Type

We can categorize refrigerators as Domestic and Commercial.

Commercial fridge consumes more power than the fridge placed in your kitchen

b) Technology

Nowadays, the latest refrigerators are coming with smart inverter technology that optimizes the functioning of the inverter and reduces energy consumption.

In this technology, the compressor adjusts its speed according to the quantity of food inside the fridge.

Therefore, reducing the energy consumption by another 10% to 20%.

c) Size

Size has a direct relation to energy consumption. Large volume fridges consume more electricity than the smaller ones.

d) Location

Keeping your refrigerator in a poorly ventilated place is a big NO.

This leads to more energy consumption.

Therefore, keep your fridge in a ventilated position.

e) Season

Seasons do affect the energy consumption of your refrigerator. The fridges consume more power in summers than in winters.

f) Usage

During summers, I open my fridge door more frequently than in other seasons.

Yes, to get a cold water bottle.

Frequent opening releases trapped cool air inside the refrigerator into the surroundings.

And the compressor needs to work harder to keep the interior cool.

This means more energy consumption by your refrigerator.

Also, when you keep the temperature too low, it will consume more energy.

Therefore, don’t set a far too cold setting.

Age

Old fridges consume more power than new ones.

Top refrigerators in India

Although, there are many refrigerator brands in India. I am listing the top refrigerator brands that are energy efficient.

Disclosure: This post contains affiliate links which means that I earn commissions from the qualifying purchases.

However, I fully recommend these products when it comes to the most energy efficient refrigerator brands.

1. Godrej
2. LG
3. Whirlpool
4. Samsung
5. Haier

(All the above refrigerators are 5-star rated products with a 1-year product warranty and 10 years compressor warranty).

Factors affecting the solar panel sizing for your refrigerator

Yes, you can use solar power to run your refrigerator smoothly.

For that, we need to have the right size of solar panels matching the refrigerator’s energy consumption.

Before sizing, let us understand the factors that affect the performance of solar panels.

i) Sunlight

The input energy of any solar power system is sunlight.

If sunlight is good, you need fewer solar panels to run your refrigerator effectively.

However, in poor sunlight, you need more solar panels to power your refrigerator producing the same cooling effect.

ii) Losses in the system

An efficient system can provide you more power with fewer solar panels than the one with more losses.

The solar power system can have many losses such as:

• Temperature related losses
• Dirt derating factor
• Shading loss
• Transfer losses
• Conversion losses

Considering all the above losses can cumulatively result in up to 20% loss in the power of the solar panels.

For example, a 400 watts solar panel with the above losses can produce 80% of 400 watts = 320 watts.

How to size solar panels for your refrigerator?

Powering your refrigerator through Solar is one step forward in saving on electricity bills.

Let us do some simple MATH:

• The average daily energy consumption of my refrigerator is 1.2 kWh per day.
• This is for the whole day that is 24 hours.

But the sun shines for 10-12 hours a day.

That means I can run my refrigerator through solar only for 10-12 hours out of 24 hours.

Therefore, I should divide the energy consumption by 2 to get its consumption in a day when the sun is in the sky.

I get 1.2 kWh/2 = 0.6 kWh

This much energy is required from solar panels to power the refrigerator in the daytime (when the sun is in the sky).

What about the remaining energy requirement of 0.6 kWh?

Either you can get it from the grid or can have a battery backup.

Sizing solar panels after considering losses in the system

Assuming, the average Peak Sun Hours in my region is 5 and the system losses are 20% (making a multiplying factor of 0.8)

The simple formula for sizing the solar panels for the refrigerator is:

Solar Panel size = Energy Consumption in a day/(PSH x multiplier)

Solar panel size = Energy consumption in a day (when the sun is there in the sky)/ (PSH x 0.8)

= 0.6 kWh/(5 x 0.8)

= 150 watts.

Therefore, I need a 150-watts solar panel to run my 150 watts refrigerator in a daytime (from sunrise to sunset).

Let us wait!

One important point is still missing.

When you start the refrigerator, it withdraws almost double the power of its rating for the first few seconds.

If your panel size is undersized, it may not provide the starting power to your refrigerator and it may not start with solar ever.

Therefore, in this situation, you need 150 watts x 2 = 300 watts solar panels to start the 150 watts refrigerator.

Thereafter, it will take 150 watts from the solar power system.

Then what is the use of the extra 150 watts that solar panels are producing?

You can use it for running your ceiling fan, a LED, etc during the day.

In total, the 300 watts solar panels are producing 0.6 kWh x 2 = 1.2 kWh or 1.2 units in a day.

You can buy 1 x 300 watts or 2 x 150 watts solar panels.

Running your refrigerator in night

For a night, you can use the grid supply to run it.

Or

In case you feel that the grid supply is irregular in your area and you need a battery backup to preserve your food.

You need to size the battery.

My refrigerator energy consumption at night is 0.6 kWh and I need 2 days of battery backup.

The formula for finding the Battery capacity (A-h) would be:

Battery Capacity A-h) = (Energy Consumption x days of battery backup)/(volts x DOD)

Profitability with Solar

A 300 watts system comes at Rs. 15,000 and it is producing 1.2 units in a day.

It means you are saving:

1.2 x 6.6 = Rs. 8 in a day

Or

Rs. 2920 in 1 year

Payback = Rs. 15,000/Rs. 2920

= 5 years.

When using solar system with battery backup add Rs. 10,000 battery cost.

The total cost = Rs. 15,000 + Rs. 10,000

= Rs. 25,000

Payback = Rs. 25,000/Rs. 2920

= 8.5 years

Solar panels are very durable with a useful life of over 25 years. After crossing payback, you enjoy free and smooth electricity for decades.

*This payback does not consider the time value of money. Also, I have not taken into consideration the maintenance cost of the system that increases when you have a battery in the system.

For more details, check out my solar feasibility spreadsheet.

Important things before buying a refrigerator

There are a few things that one should keep in mind while buying a refrigerator.

i) Capacity

It refers to the storage of your refrigerator in liters. It is a sum fridge and a freezer capacity. The capacity required depends on your family size.

When you have more than 4 members then a 200+ liters refrigerator is preferable.

If you store more vegetables then look for the bigger capacity fridge.

Whereas, a large freezer is for those who eat more frozen products.

ii) Defrosting type

Defrosting is the process of removing extra ice from the refrigerator.

We have two types of defrosting mechanisms in refrigerators:

• Frost free
• Direct cool

The direct cool refrigerators use the natural convection technique to eliminate the buildup of ice.

It preserves food for a lesser duration but is more energy efficient.

Also, you need to defrost the ice manually periodically.

Whereas, frost-free refrigerators use electrical fans to remove extra ice.

It keeps stored food fresh for a longer duration.

Also, there is no need to manually defrost it, it automatically does.

But it consumes more energy.

iv) Door type

We see different door types of refrigerators in the market such as:

Mini door, Single door, double door, triple door, French door, etc

v) Look for smart Inverter compressor technology

The is an intelligent compressor technology. In this, the compressor reduces its speed when the temperature falls below the set limit and switches to the full capacity when more cooling is required. This feature helps in saving about 20-30% of the energy consumed. Also, they are less noisy and have more life span.

vi) Other features

Other salient features that can affect your buying decision are a number of shelves, vegetable storage, Toughened glass shelves, water, and ice dispensers, cool pack, curd maker, convertible refrigerator/freezer.

Key takeaways

• Manual defrosting is more energy efficient
• Look for refrigerator based on your needs like capacity, door type, technology, etc.
• In the evening you can either use battery or grid to power your refrigerator.
• Solar panel sizing for day time = Energy consumption day time/(PSH x 80%)
• You need to multiply this size by 2, because refrigerator needs double current for few seconds to start.
• The extra power thereafter can be used to run other electrical appliances such as fan, LED, etc.
• Look for energy efficient solar panels