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Grid tie inverter and prepaid electricity meter


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I've bought myself a second hand grid tie inverter for the purpose of saving electricity. No battery bank backup is planned. Just want to feed solar into my house grid during the day to bring down electricity bill. Now the installers tell me it is not going to work because we have prepaid electricity and is going to trip te prepaid meter.  Need advise please. 

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15 hours ago, Raakvat said:

Now the installers tell me it is not going to work because we have prepaid electricity and is going to trip te prepaid meter

some "one way" pre paid meters do indeed trip when they detect reverse feed. Please give us the details of the pre paid meter and inverter you have.  

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  • 1 month later...

Hi yes there is a way around this issue  so let's say you maybe want to only do the lights ...by taking out the feed in your (DB box )of the lights and running it directly from your setup you will not be able to run the whole house what you basically doing is running the lights then on it's own circuit  hope this helps 

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  • 4 months later...

Hi

I installed a 3-phase Zeversolar grid-tied inverter at my place in Noordhoek, CT some years back.  By adding a DIN rail energy meter to the house input, and a ZeverCom control unit it was possible to configure the inverter to ensure no export. I used it for 3 years with a prepaid meter, with no issues.

Ian  

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15 hours ago, Solarsmit said:

Hi guys,I have a customer that has prepaid,i was thinking of taking his lights and some of the plugs off prepaid,Splitting his DB.What other suggestions do you have?

is this a grid parallel hybrid system? If it is and the prepaid meter trips i think to move the lights and some plugs to the back up (essential loads) output will not solve the tripping problem. The grid tied inverter is downstream of the prepaid meter and the occasional small amount of reverse feed (even if the inverter is set to zero export) is inevitable. The best solution would be to discuss this with the municipality and hopefully get them to deactivate the reverse feed tripping or install a less sensitive meter. Another option (based on some PF members feed back) is to permanently run a small load (like a incandescent light globe). 

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What if it's a municipal pre-paid meter? That's what I have,  and there's no choice. I'm in Johannesburg and it's an Itron meter.

What I find is that the meter always supplys power but it doesn't recognise the small amount that gets exported (my inverter tries to zero the meter each day). So there is a small loss there (maybe .25 kw/h/day in a bad week). 

Also the actual interface unit doesn't handle the situation very well. It repeatedly boots and shuts down (it seems that a feedback into the grid, no matter how small, causes the trip). So I mostly leave it off. But if I want to get a reading (which I do once a week) or load electricity then I have to plug it in, wait for it to have a stable 30 seconds or so and then work very quickly.

I buy prepaid because we still use a little grid power each week (more in overcast weather) and I want to build up a credit now (the Itron lets you accumulate 10 000 kw/h IIRC) to offset price increases in the future.

Edited by Bobster
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33 minutes ago, Bobster said:

What if it's a municipal pre-paid meter? That's what I have,  and there's no choice. I'm in Johannesburg and it's an Itron meter.

From what I gather some municipalities might disable the feedback trip assuming the meter can have it disabled. But I will not pin much hope on this option.

The other option is usually to have the pre-paid meter replaced with a four-quadrant electricity meter. Seems like municipalities at one stage footed the bill for this but mostly the user need to cough up R6000-R8000+ for this. If in any way connected to the grid (for the geyser, cloudy weather etc.) I will however NEVER return to a non pre-paid meter (meter reading issues, billing chaos etc).

40 minutes ago, Bobster said:

But if I want to get a reading (which I do once a week) or load electricity then I have to plug it in, wait for it to have a stable 30 seconds or so and then work very quickly.

Switch on a heavy power appliance like the oven for a minute if needing to do this during the day? Reading/loading when PV production is low (i.e. night)? If possible having loads spread out on timers might be worth a try (washing machine 09:00-10:00, Pool pump run 10:00-14:00, Geyser 14:00-15:00) but it will be a fine ballancing act.

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21 hours ago, introverter said:

From what I gather some municipalities might disable the feedback trip assuming the meter can have it disabled. But I will not pin much hope on this option.

The other option is usually to have the pre-paid meter replaced with a four-quadrant electricity meter. Seems like municipalities at one stage footed the bill for this but mostly the user need to cough up R6000-R8000+ for this. If in any way connected to the grid (for the geyser, cloudy weather etc.) I will however NEVER return to a non pre-paid meter (meter reading issues, billing chaos etc).

Switch on a heavy power appliance like the oven for a minute if needing to do this during the day? Reading/loading when PV production is low (i.e. night)? If possible having loads spread out on timers might be worth a try (washing machine 09:00-10:00, Pool pump run 10:00-14:00, Geyser 14:00-15:00) but it will be a fine ballancing act.

Thanks, I shall try this.

Though the extravagance will bother every bone in my parsimonious being.

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11 minutes ago, Bobster said:

Though the extravagance will bother every bone in my parsimonious being.

Obviously if you have a system that allows you to know what your PV production is like and what your loads are then switching on the oven when a toaster will do is outrageous! 😉 toaster even has a built-in timer function....

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  • 6 months later...
On 2020/06/21 at 10:59 AM, Bobster said:

What if it's a municipal pre-paid meter? That's what I have,  and there's no choice. I'm in Johannesburg and it's an Itron meter.

What I find is that the meter always supplys power but it doesn't recognise the small amount that gets exported (my inverter tries to zero the meter each day). So there is a small loss there (maybe .25 kw/h/day in a bad week). 

Also the actual interface unit doesn't handle the situation very well. It repeatedly boots and shuts down (it seems that a feedback into the grid, no matter how small, causes the trip). So I mostly leave it off. But if I want to get a reading (which I do once a week) or load electricity then I have to plug it in, wait for it to have a stable 30 seconds or so and then work very quickly.

I buy prepaid because we still use a little grid power each week (more in overcast weather) and I want to build up a credit now (the Itron lets you accumulate 10 000 kw/h IIRC) to offset price increases in the future.

Hi Bobster I have the same setup - Itron prepaid City Power meter and my Victron setup has the ability to feed back. I spoke to a city power technology department today and the lady advised that there are no plans to allow feedback or payment for feedback on prepaid systems - mentioning the billing issues and the fact prepaid does not include a monthly connection fee so the city makes nothing from these customers using the grid as backup.

 

Anyway they are busy working on the billing system to allow for the payment of power feedback tariffs on post paid accounts (I saw around R 0.50 per unit in the latest tariff sheets) so not much if you would need to pay the monthly connection fee of around R800 on a post paid account.

 

What I found interesting is you mention that there is a problem with the display unit when you feed back power, but that your meter does not trip - does that mean that your meter is able to run backwards so your usage and production cancel each other out on a daily basis? This is something I would like to do but worried that the meter will use units regardless of whether I am consuming or producing power. I would like to feed back to make my system more efficient as it is constantly reducing and increasing output based on household load at the moment.  Do you recommend I test the feeding back and check what the meter does?  

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On 2021/01/12 at 1:50 PM, Dman said:

Hi Bobster I have the same setup - Itron prepaid City Power meter and my Victron setup has the ability to feed back. I spoke to a city power technology department today and the lady advised that there are no plans to allow feedback or payment for feedback on prepaid systems - mentioning the billing issues and the fact prepaid does not include a monthly connection fee so the city makes nothing from these customers using the grid as backup.

 

Anyway they are busy working on the billing system to allow for the payment of power feedback tariffs on post paid accounts (I saw around R 0.50 per unit in the latest tariff sheets) so not much if you would need to pay the monthly connection fee of around R800 on a post paid account.

Exactly. They have a tariff that allows selling back, but it will cost me the required meter and a flat monthly fee and there is no way that I would even break even on that. So I don't resell. 

The municipality have tried two years running to introduce a flat monthly fee for pre-paid meters.

In 2019 plans for the flat fee were revealed by the press who had read the document detailing the new tariff structures. The idea was to add R200 a month to the rates bill for properties with pre-paid meters. The then management went into panic mode and told us that somebody had snuck this into the budget after they had signed off (yeah right). 

in 2020 they announced the flat fee (R200 again) but then waived it as part of the Covid relief package.

I expect it to reappear soon.

They still bear the cost of providing and maintaining a feed to my property, so I can sort of see their point. I will grumble, but I will still be saving so I will just grumble.

On 2021/01/12 at 1:50 PM, Dman said:

 

What I found interesting is you mention that there is a problem with the display unit when you feed back power, but that your meter does not trip - does that mean that your meter is able to run backwards so your usage and production cancel each other out on a daily basis? This is something I would like to do but worried that the meter will use units regardless of whether I am consuming or producing power. I would like to feed back to make my system more efficient as it is constantly reducing and increasing output based on household load at the moment.  Do you recommend I test the feeding back and check what the meter does?  

My meter is the Itron. On the hand-held display it has a count of units used since installation at the top.

Towards the bottom it has a balance of pre-paid credits loaded on the meter.

If you just have prepaid and no solar then the top number will increase and the bottom number will decrease and they do so at the same rate.

My system is set to not export, but it uses a little grid each day and so tries to zero the meter each day and feeds a small amount back into the grid. What I now find is that my pre-paid credit drops faster than the total used increases. It's a small discrepancy, and I am assuming that when power is fed back it decreases the total usage but has no affect on the pre-paid balance. It's a few rand each month and it's not nearly enough to justify going over to the reseller's tariff. 

Also when I have a lot of solar the hand-held unit keeps on rebooting, but as far as I can tell the actual meter (in the municipal box on the wall) is unaffected.

This may be peculiar to the Itron meter. 

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17 hours ago, Bobster said:

My system is set to not export, but it uses a little grid each day and so tries to zero the meter each day and feeds a small amount back into the grid. What I now find is that my pre-paid credit drops faster than the total used increases. It's a small discrepancy, and I am assuming that when power is fed back it decreases the total usage but has no affect on the pre-paid balance. It's a few rand each month and it's not nearly enough to justify going over to the reseller's tariff. 
 

That discrepancy between the total usage and pre-paid balance may be due to the fact that some meters read import and export of power as consumption, and hence you are 'charged' for what you feed back. This is what I want to test on my system.

I agree that it makes more sense to pay a bit towards prepaid rather than be tied to the post paid and all it's costs and issues, however I am considering registering my system as a way to feed back to the grid for free (i.e. without being credited for the power) as this would allow my system to operate much more effectively. The problem with using a power meter to balance consumption and grid is that the inverter is always reducing draw from the panels to match consumption instead of just always drawing the power available and sending that easily to the house or excess to the grid. I can only do this is I won't be charged by my meter for what I feed back.

My concern is if I register ( which involves having the installation signed off) is that then I will be on the books, so to speak and if the council ever decided to tax people with solar installations I would already be on the list of solar households (you never know I have seen talk of charging solar users.....).

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