I live in Johannesburg and pre-pay for my electricity. I have a hybrid solar system. This actually still uses a small amount from the grid, and the inverter attempts to send back enough power, when it has a surplus, to reverse what is used from the grid.

Here's what happens. 

Say at the start of the day the meter sits at 123456.78 kw/h used and my prepaid balance is sitting at 5431 kw/h.

During the day the inverter pulls 2 kw/h and sends back 1.

The meter itself increases by a net 1 kw/h, IE at the end of the day it is 1234567.78. But the credit balance is unaffected by the power sent back and thus is reduced to 5429 kw/h. So I actually get no credit for the 1 kw/h sent back.

Sounds about right. More knowledgeable people will also comment but some of the cheap pre-paid meters does not measure the flow direction. It just calculate what is moved through the meter in this case it is 3kw.

 

 

14 minutes ago, Luminous said:

Sounds about right. More knowledgeable people will also comment but some of the cheap pre-paid meters does not measure the flow direction. It just calculate what is moved through the meter in this case it is 3kw.

Interesting. I assumed it was a case of it only "seeing" the flow in one direction. It didn't occur to me that it might see all flow and regard it as use. What I see is the credit balance going down faster than the actual consumption on the meter.

The amounts are real, but small. It is going to take a whole lot of paperwork and cost me R250 a month extra to go back to postpaid where (I presume, but don't know) I won't have this problem. 

Edited July 3, 20196 yr by Bobster
Got it wrong.

I might add that I think the meter does "see" the direction of the flow, because I regularly get messages on it to the effect that it has detected an export of energy. Sometimes it will even show a negative figure for the amount being consumed at the moment. So I think it's a glitch in the software as regards pre-paid credit.

Edited July 3, 20196 yr by Bobster
spelllling

Some meters trip. Some meters bill you for the energy. And some simply clamp it at zero. No electronic meter (except those made for the purpose) is going to count in reverse. Not going to happen. The engineers already thought of that, one of the major reasons for moving away from the disk-style meters is to avoid such tampering.

Note, not saying that feeding in energy is tampering. I'm saying there are ways of tampering with the meter to make it spin backwards, and it happens to use the same mechanism as your embedded generator 🙂