How does a bidirectional electric meter know which way the power flows?

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After installing solar panels on my roof I got my electric meter replaced with a bidirectional one. This meter can measure both energy that I draw from the network and the energy that I send, depending whether my consumption is higher or lower than my production.

It got me thinking though. If the network uses AC which has no constant direction, then how can a meter by measuring the current and voltage know if the power is consumed or given back?

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4 Answers

Anonymous 0 Comments

The power meter will measure both current and voltage. When you are using power the current goes into your house when the voltage is positive and out of your house when the voltage is negative. But when you are making power the current goes out of your house when the voltage is positive and into your house when the voltage is negative. The meter will either measure the voltage and current very regularly and calculate this for each sample, or there are analog circuits which can multiply current and voltage and then do analog integration for the meter to read every once in a while.

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