What is EC?

In hydroponics, EC is the measurement of electrical conductivity within your nutrient solution. (It may also be shown as CF, for conductivity factor.) So whilst checking pH levels gives a good indicator of the balance of your available nutrients, EC gives you an idea of the quantity of available nutrients.

Pure or distilled water has no electrical conductivity as it contains no minerals. Once minerals are added into water, the dissolved salts allow it to conduct electricity. The higher the concentration of salts, the higher the electrical conductivity. Measuring this tells you how much nutrient there is in the water. For most plants you want the EC measurement to be hitting between 1.2-1.6 during the vegetative stage and 1.6-2.4 during flowering, but this can be dependent on the type of plant that's growing. Here's a list of target EC ranges for different plants so worth checking as tomatoes can handle an EC up to 2.8, spinach as high as 3.5, whereas basil it should be no higher than 1.4.


Growth Technology Conductivity Standard - shop now

Bluelab CF Truncheon - shop now

Bluelab EC Pen - shop now

Why is EC important?

Measuring the EC means you get a more detailed idea of what is actually happening within your nutrient feed – more so than just taking the pH reading alone. Over time your EC will either stay the same, go down or go up and this is why you need to measure it regularly.

  • If the EC measurement stays the same it shows that the plant is using as much water as it is nutrient, and is balanced. Keep the nutrient tank topped up with the solution of the same strength to keep this balance but check regularly to ensure everything is still working as it should.
  • If the EC measurement goes down it indicates that the plant is using up more nutrient than water. You should top the nutrient solution back to what it was, and possibly even try a stronger nutrient solution feed. If you do increase the strength, watch the EC closely to see how your plant is reacting.
  • If the EC measurement goes up your plant is using more water than a nutrient, and it isn’t taking up what it should be. You need to add more water to dilute the solution down. Burned leaf tips and slowed growth can be signs of over-feeding and if so your nutrient solution may be too strong. Temperatures can also affect this, and on hotter days your plants may take up more water.

Reading EC with a Budget Pen in an OxyPot

If you don’t change your nutrient solution regularly, and just top up when necessary, you could be putting your plants at risk of toxic nutrient levels. EC measures the number of nutrients available but doesn’t tell you how much of each individual element is in there. You could have the perfect EC measurement but still have nutrient deficiencies. It also doesn’t tell you if certain elements or waste have built up to high levels, which could further damage your plants.

You need to measure the conductivity every day, topping up nutrients when necessary and doing a complete nutrient refresh every 7 days by emptying your tank and creating a new solution.

How to measure EC?

The easiest way is by using a digital meter, such as the Bluelab CF Truncheon. These work by measuring the electrical conductivity via the electrodes on the bottom of the meter. All you need to do is dip the end into your solution and check the digital reading.

Conductivity should be measured every day so you can keep an eye on what is happening. Things can easily change from one day to the next when growing with hydroponics, and you want to be able to catch any problems as soon as they arise.

To ensure your EC metre is always delivering accurate readings, regular cleaning and calibration is necessary. If you are unsure about doing this yourself, then pop into any Holland Hydroponics store and one of our team would be happy to assist you with our free calibration service.

Shop products:

Budget EC Pen

Bluelab CF Truncheon

Bluelab EC Probe Care Kit

Growth Technology Conductivity Standard