Bi-directional electricity meter to measure energy imports and exports?

[Arthur]

I'm implementing an 8kW PV array, with grid-tie via an MLT Drives PowerStar 12kW grid-tied bi-directional inverter that manages syncing, islanding, etc. The only challenge we face is how to handle nett metering.

Anyone know, or know someone, where I can source a suitable meter that the local municipality can install? Ideally the meter should measure both energy imports and exports to the grid, with a nett metering reading that can be read by the utility meter reader.

My supply is single phase 60A currently metered by a Plessey pre-paid ECON model. It cannot handle energy exports and immediately goes into 'tamper' mode when energy is exported from the SSEG to the utility.

My municipality is loathe to use an old rotating-disc electro-mechanical meter as these are not very accurate, apparently.

Any pointers, contacts or shared experience most appreciated.

[ambo]

The digital smart meters that are used for metering large business and industrial users support this. The municipalities have their preferred vendors for these and I'm sure you could request that they install one. Its not likely to be a prepaid meter, I've only seen postpaid. Unless you have an agreement with your electricity provider to feed power back into their grid the meter will probably still flag a fault.

[Fudzy]

Four quadrant meters (bi-directional) are helluva expensive too. From what I've read they mostly use them to bulk meter complexes which have solar arrays, the munic has to give you permission to supply onto the grid as well IINM.

[Arthur]

Thanks, gents. I have an agreement with the local utility to export - we're just looking for an appropriate meter. One of the concerns is if exports substantially exceed imports then I can end up with a massive (erroneous) bill when the meter clicks backwards from 00000 to 99999. I have spent hours trying to get info from suppliers like Landis+Gyr, but their reps know nothing and cannot be less helpful (shocking - I'm writing to their HQ to report their pathetic local branch/agent).

[Fudzy]

Thanks, gents. I have an agreement with the local utility to export - we're just looking for an appropriate meter. One of the concerns is if exports substantially exceed imports then I can end up with a massive (erroneous) bill when the meter clicks backwards from 00000 to 99999. I have spent hours trying to get info from suppliers like Landis+Gyr, but their reps know nothing and cannot be less helpful (shocking - I'm writing to their HQ to report their pathetic local branch/agent).

Don't think the meter would use mechanical digit display.

[Arthur]

I eventually got hold of the tech boffin at Landis+Gyr. He was most helpful, and a mine of information. He recommends either the ZMG300 or ZMD300 range. These are 4Q 3-phase meters, but can be used for a single phase. Pricing is well under R3K for the meter, plus extra for the comms modules and software, if required. I want the Ethernet comms module. Will go for this if the local municip agrees.

[Beachless]

How did you arrange this with the utility company?

I wish they would allow us to put back into the grid, then I would have installed Panels a long time ago.

[Messugga]

I eventually got hold of the tech boffin at Landis+Gyr. He was most helpful, and a mine of information. He recommends either the ZMG300 or ZMD300 range. These are 4Q 3-phase meters, but can be used for a single phase. Pricing is well under R3K for the meter, plus extra for the comms modules and software, if required. I want the Ethernet comms module. Will go for this if the local municip agrees.

Having comms on these meters is pretty cool. Often they charge you separately for the protocol the units use, so unfortunately in that case having your own implementations chatting with the meter becomes prohibited by pricing.

[Arthur]

How did you arrange this with the utility company?

I wish they would allow us to put back into the grid, then I would have installed Panels a long time ago.

Drafted a detailed project plan, with all specs, equipment, references to various policy docs (such as NRS 097-2-1:2010), etc, set up a meeting with the Chief Electrical Engineer, and an hour later we shook hands. We only need to solve metering and billing. The basic policy is that one must be a nett consumer, ie they won't pay back if exports exceed imports.

If I manage this properly my electricity bill should equal the basic fixed charge, which is unavoidable when not using pre-paid.

As to the cost-effectiveness: I already have the grid-tied inverter that manages exports. Putting say R100K into panels will return at least 25% per annum guaranteed, increasing with each passing year. One cannot get anything near this after tax by going to the market.

[lucifir]

can you give us an idea of your setup and costs??
also which muni is this that allowed you to go this route(for others wanting to take this route)??
I would also like to go this route, but the setup cost seems prohibitive ... so gonna try going small at first and see how that works out

[Beachless]

Drafted a detailed project plan....

Thats quite interesting, I've seen a few articles about groups trying to achieve this but not being able to come to an agreement.
Which company was this?

I use very little power and a 3-4KW would probably put me near the breakeven point which is like R40000 in panels(exl the other infrastructure)