What is a CT ratio reading?

  • 16 November 2017
  • 9 replies

  • Carbon Cutter*
  • 2 replies
Hi does anyone know what a CT Ratio reading is ???????

Since feb this year my meter hasn’t been working properly. After numerous visits from OVO and now from Western Power I’m told I need to get my own Electrition to find the CT Ration on my meter ??????

However no one seems to know what it is ????? Really??? 😤😤

Best answer by Markee 16 November 2017, 17:35

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9 replies

Userlevel 2

Updated on 13/09/23 by Abby_OVO 


As CT ratios are not something that usually affect domestic supplies, OVO members shouldn’t need to worry about this calculation. There’s some helpful advice in understanding what a CT ratio is in the comment below.


A CT Ratio is where the reading into a meter is adjusted according to the measurement device.

A CT is a Current Transformer, and is the ferrite core that wraps around your supply cable and sends the reading of what your current consumption is to the meter.

The connection between the CT and a meter is normally 5A. If you have a 100A supply, the CT Ratio is 20:1.

Why you would need any involvement in CT Ratios is a mystery though as most domestic electricity meters are direct connect meters and don't use CTs.…


If you’re experiencing issues with your meter following an engineer visit , reach out to our Support Team who’ll be able to investigate further with full access to all job reports received from the engineer who attended.

Thank for that. I’m confused too !! It’s a old economy 7 day/night meter and one of the dials has stopped moving. Apparently tho it’s a Phase 3 meter ?? Still no idea why it’s taking 9 months to sort !!!
Userlevel 2
Assuming it’s domestic premises (ie your house):

It’s HIGHLY unlikely:

1. Economy 7 meter will use CTs.
2. Your supply is three phase.

Do you have a picture of the meter you can post?
Pretty old !!
Userlevel 2
That meter is neither 3 phase, economy 7 or has CTs.

Someone’s spinning you a bit of a yarn...
I also have the same problem with how to calculate kwh if my electricity meter CT 400/A?
Anyone can help me? Because on the meter seem running to slow but billing issue too high
Userlevel 6
Hey @somethea,

CT ratings and kWh calculations are not something our customers generally need to do, we don't offer commercial supplies and these connections aren't normally used on domestic properties as @Markee rightfully mentioned.

If you think your meter has CT's, please pop our team a message on Facebook, they'll take a further look into this for you.

Userlevel 5

Pretty old !!


 @Mel  @Markee

FYI that meter has two readings on it so it looks like it's probably Eco7.


Userlevel 7

This is another old but popular topic - has ANYONE needed to know what a CT rating is in 2020? 


If you have a smart meter…. I think not…. :thinking: