Understanding Electrical Conductivity (EC) in Hydroponics

EC indicates the salt level in your nutrient solution and tells you how strong or concentrated the nutrients are.

Does it sound abstract and confusing?

Read on, and I will explain.

Essentially, EC tells you how many nutrients there are in your water.

  • High levels mean more nutrients
  • Low levels mean fewer nutrients

I have had EC explained to me by professors and have left the conversation more confused than enlightened. 

This article is written to demystify EC.

I will start by explaining EC in an easy-to-understand way before moving on to more advanced stuff.

This way, we all have an understanding before we look at how, when, and why we should manage EC, as well as its limitations.

Would you prefer a hands-off solution to hydroponics? Here are some tips on choosing a small hydroponic kit where you will be up and running in less than an hour.

What is Electrical Conductivity (EC)?

Electrical Conductivity (EC) is like a nutrition scanner for your plant’s water in hydroponics. It’s all about ensuring your plants get their proper meals – the nutrients.

Here’s how it works, simplified:

Think of your hydroponic garden as a kitchen; the water is like a soup you cook for your plants. The ingredients in the soup are the macro and micronutrients your plants must have to grow.

When these ingredients (or nutrients) dissolve in the water, they break down into tiny charged particles called “ions”, almost like sugar dissolves in tea. Each of these particles carries a little electric charge.

Plants need nutrients to develop healthy roots systems
Balanced nutrients give healthy root systems

EC is like a detector counting your soup’s charged (nutrient) particles.

A higher value means there are lots of nutrients, and a low value means there are fewer.

Your nutrient solution is too rich if the detector finds too many charged (nutrient) particles.

A bit like accidentally dumping too much salt into a pot – the “soup” becomes too “salty,” and plants can get overwhelmed, dehydrated, or even experience “nutrient burn.”

But if you do not have enough charged (nutrient) particles, your plants are left hungry, causing imbalances, nutrient deficiencies, and stunted growth.

And to make sure your plants are happy, you adjust how much you feed your plants (add nutrients) based on what the EC detector tells you.

This way, you are always sure your plants get the right amount of food without overfeeding or underfeeding them.

What EC means to you: Using the readings

All gardening is about incremental changes, observation, and adjustments.

Sudden changes in anything from nutrient, pH or temperature can cause stress.

In the same way, EC is not just about exact numbers. You have to think in terms of trends and changes.

I will give you three scenarios with different trends:

  1. You have a steady EC: A constant reading is a green light. Your plants are sipping water and nutrients at an equal pace and you have found a perfect balance. Your job is to keep the nutrient tank filled with a same-strength solution and monitor for changes.
  2. The EC is dropping: Your plants consume more nutrients than water. You must top up the nutrient tank to its original strength and maybe even consider a slightly stronger mix. But do not go overboard; always make small adjustments. 
  3. You see rising EC levels: A climbing level is a sign that your plants drink more water than nutrients. Add more water to dilute and balance the nutrient solution. Watch for signs like burnt leaf tips or slowed growth; they could tell you it’s time to start over with a fresh mix. 

Now that you know how EC can be used, let’s look at how you can measure it.

Besides my DIY hydroponic garden, I also have two smaller countertop hydroponic systems.

How to measure EC levels in your nutrient solution

To measure the concentration of salts or nutrients, you need a special device called an EC meter. Today, most devices measure both pH and EC. 

Measuring is as easy as dipping the probe in the nutrient solution and observing the reading.

Measuring and adjusting EC levels
Measuring and adjusting EC levels

Devices come in different shapes and forms, from handheld pens to wall-mounted digital control panels.

I will write an article about the EC meter I chose and why. But for now, I will point out two important points:

  1. Calibrate before use: Use a pH-neutral solution like distilled water (not tap water) and calibrate your EC meter to show a perfect pH 7 for neutral before measuring your tank’s nutrient level.
  2. Store properly: Some EC meters should be stored dry, while others must be covered directly after use. Read and follow the instruction manual carefully. 

By now, you probably think EC is the answer to all kinds of problems. You are not wrong, but there are also limitations.

What are the limitations of EC in hydroponics

There are four limitations you should be aware of: 

  1. It does not tell us everything: EC gives us an indication of nutrient strength, but it does not tell us which nutrients are present or missing.
  2. Changing plant needs: Plants have different nutrient needs at various stages of growth. EC does not adjust automatically, so we have to.
  3. Water quality matters: The quality of your water can impact EC readings. Start by measuring your water for a baseline.
  4. Only measures electrically conducive minerals: EC does not give a complete measure as it only measures dissolved minerals that conduct electricity. 
NFT hydroponic setup
NFT hydroponic setup

Next, we look at TDS and PPM – two terms you have probably already encountered.

Measuring the EC vs TDS and PPM?

Same, same, but different come to mind. A bit like different units for measuring distance – kilometers, miles, and meters all measure length, but they are not the same.

Electric Conductivity (EC):

  • As you know by now, EC measures how well water can carry an electrical current to indicate nutrient strength.
  • It’s measured in units called Siemens or millisiemens per centimeter.

Total Dissolved Solids (TDS):

  • TDS counts all the dissolved stuff in the water, not just nutrient ions that conduct electricity.
  • It is often measured in parts per million (PPM).
Monitoring hydroponic basil
Monitoring EC and pH levels

Parts Per Million (PPM):

  • PPM is a way to express the concentration of dissolved substances in water (including nutrients).
  • It is a unit used to measure TDS but can also apply to EC measurements.

These terms tend to be used interchangeably, but they are not identical.

But enough semantics, let us address the elephant in the room: does EC equal nutritional value?

Is the EC value the same as the nutritional value?

The short answer is no. It is important to distinguish between nutritional strength and value or content.

EC gives you a useful measure of the nutrient strength in your hydroponic solution. But it does not tell you the exact nutritional content or value. 

Think of it as knowing how much gas you have in your car. You know how much gas you have, not the proportions of oil and other petroleum liquids.

EC also tells you how “full” your tank is but does not specify the exact nutrient proportions.

Now that we know the difference between nutritional value and strength- let’s dive into the practical side: how do you adjust the value?

How to reduce or increase the EC value

Adjusting the value is easy – the tricky part is to get it right. The process calls for patience and small, incremental changes.

To Reduce EC:

  • Dilution: Adding more fresh water to your nutrient solution is the most straightforward way to lower the concentration of nutrients. It is no different than adding more water if your juice is too strong.
  • Add lower-strength nutrients: Top up using a milder nutrient solution with lower strength, like using less salt in your cooking.
Fixed EC meter
Fixed EC meter

To Increase EC:

  • Concentration: Add more nutrient solution to your mix if levels are too low. It is like making your coffee stronger by adding more coffee grounds.
  • Stronger Nutrients: You can also opt for a stronger nutrient formula with higher nutrient strength.

Again, adjustments must be made gradually to avoid shocking your plants. Keep an eye on their reaction and monitor for any signs of stress.

Ok, let’s round off by answering the million-dollar question: is an EC meter is a must-have for your hydroponic setup?

Do I need to buy an EC meter?

If you run a commercial hydroponic garden, you check salt concentration and dissolved salts at least once daily. And you would take action if the nutrient solution fell outside the optimal range for your specific plants. 

But when growing at home for personal use, you do not have to buy an EC meter. You probably will at some point, but there is no stress. And here is why:

As a home grower, you will use ready mixed nutrient solutions that give good results without detailed EC tracking. The hydroponic fertilizers you buy are designed to balance nutrient levels for you.

For me, an EC meter was right there on the list after full spectrum grow lights, growing medium and hydroponic fertilizers. 

You can get far by just observing your plants. Signs like strong growth and green leaves usually mean your nutrient levels are okay. 

As you get more experienced, you might want an EC meter for more control. But in the beginning, it is not a must.

You can learn a lot from observing how plants grow and develop. Wilting, yellowing leaves, slow growth, brown edges, and smaller-sized new leaves are all signs that something is not right. 

Key Takeaways:

  • EC, or Electric Conductivity, measures nutrient concentration in your hydroponic nutrient solution.
  • Regularly monitoring and adjusting EC helps give your plants the right amount of nutrients.
  • Understanding the difference between EC, TDS, and PPM is helpful for effective nutrient management.
  • EC is not the same as knowing the exact nutritional value. There is a difference between value or content and strength.
  • You can reduce or increase the EC value by adjusting the nutrient solution’s strength or diluting it with fresh water.
  • Whether you need an EC meter depends on your experience level and desire for precise hydroponics nutrient management.

EC is like a compass in your hydroponic journey, guiding you towards healthier, more productive plants. It may not be essential for beginners to hydroponics, but it is helpful for all-level growers. 

With a deeper understanding of EC, let’s look at pH. If EC is about how much food your plants have, pH levels can tell us how well they can access that food.

Mattias Magnusson: Hello, I'm Mattias, a passionate and experienced gardening enthusiast. I am the creator of MattMagnusson.com, your guide to year-round herb and veggie growing. Let's simplify green living, no matter your space or location.