[Rovarious]

Now that 3-phase domestic smart meters are being fitted can anyone confirm the billing policy applied by e.on (and others) when importing on one or more phases and exporting on the others?

Because we have three phase solar and single phase ovens etc. it is possible that:

• Phase A is importing 1 kW
• Phase B is importing 1 kW
• Phase C is EXPORTING 1.5 kW

With NET billing the charge would be 1 + 1 - 1.5 = 0.5

With billing by phase the charge would be 1 + 1 - nil (as exporting) = 2

I asked Ofgem what it should be and eventually got the following:

Suppliers may deduct the export value from the import value and bill based upon the remaining value, or bill the import figure separate from the export figure depending on the contract arrangement, and whether the contract is domestic or non-domestic.

In general, we state suppliers may only charge for actual energy usage, or where actual figures are not available, suppliers may use estimated figures based upon reasonable accurate calculations.

The red highlight is mine - The response implies that e.on and others should use net metering - but do they?

I suspect that my dumb meter (a Landis & Gyr 5219a) counts all import and ignores export so a smart meter that does net metering should save me a few pence.

Any info/confirmation would be appreciated.

[wizzo227]

The 20th century three spinning discs on a common shaft type also does net power, and ought to spin backwards when net generating.
They hastily scrapped most of those when the possibility of generating became apparent. I got a firm no when asking a fitter for a scrap one.
Beware that Ofcom might not have updated all of their documents. I noticed a single-phase smart meter at a friends' house showing 0.00 when there was a lot of sun on the solar panels and definitely net generating. Summing such a software zero against import kW numbers on the other phases would definitely get a more expensive number than would net power, so in my opinion you would be correct to seek any other use of your surplus than to throw it away for free, unless EoN can confirm in writing that they are going to supply a three phase meter and a contract which will do either net power or metered export. Electromechanical machinery can move your surplus to other phases, at such low efficiency that if you are not a ship then it isn't worth doing that. A box of switches often called a "solar diverter" can drop the surplus generation within one phase to an immersion heater or comparable interruptible load. Beware that some pretty insulting prices for exported kWh units sometimes get offered by EoN.

[Rovarious]

Thank you @wizzo227. I did get a 'reply' from E.ON Next

The phase of the meter doesn't make a difference to the billing. The phase is more about the amount of energy that the meter can deal with.

Which is clearly absolute nonsense both electrically and common sense - and shows the customer service rep didn't read the question. I have replied and asked them to 'escalate' - we will see if I get a more sensible answer.

[meldrewreborn]

@Rovarious

Good luck with that! We’ve been told in the past that all energy specialists are trained to the same standard and that there are no supervisors!

Volunteers here can often suggest solutions to problems but have no mechanism to implement, and we’ve been firmly told that the forum is not a back door entry to customer service- although exceptions are sometimes made.

[Rovarious]

So, I tried telephoning...

Smart metering said 'we can fit a 3 phase meter' but you will need to speak to billing about net metering... let me transfer you...

Billing said "I'll transfer you to smart metering", and when I said "they just transferred me to you" said "wait while a consult a colleague" followed (after a bit of a wait) with "I'll transfer you"...

... to the Solar team who didn't know the answer but "hold for a second while I consult a colleague"... wait, wait, wait some more - and then halfway through a recorded message absolute silence - looks like the call got lost in the system.

I't does look like solar _might_ know the answer (even though I have a Feed in Tariff rather than smart export) - I'll try again after lunch

[retrotecchie]

Originally Posted by Rovarious

Thank you @wizzo227. I did get a 'reply' from E.ON Next



Which is clearly absolute nonsense both electrically and common sense - and shows the customer service rep didn't read the question. I have replied and asked them to 'escalate' - we will see if I get a more sensible answer.

Badly worded, but there is an element of logic there. Single phase supplies are usually rated at 100 amps which limits you to a maximum load of around 25kW. Three phase supplies are fused at 100A per phase, increasing the maximum total load to around 75kW.

Three phase metering (of which I am conversant with in commercial and domestic settings) is, or should be, net metering.

Problems can sometimes happen if you are importing on two phases and exporting on a third as it throws things out of balance, but at a household level that isn't so important. Commercial and industrial premises usually have load balancing equipment to switch some loads between phases in order to keep things balanced, but for loads or sources below 7.5kW it's not that important. Things can be done elsewhere to balance phases.

So, you are looking at net metering, but exports and imports are paid for and/or billed separately so it's a bit of an irrelevance really. You are billed on net energy imported across all three phases. You are paid under a separate account (FiT or SEG) for energy exported. You don't get your exports directly deducted from your imports. They are managed independently of each other.

[Rovarious]

Thank you @retrotecchie - I understand your translation of the E.ON Next 'reply' - if that is what they meant to say it was poorly worded.

Our installation is fairly well balanced. The big users (EV and Heat Pump) are three phase and equal across the phases. Things like ovens, washing machines and immersion heaters etc. are single phase which can cause us to be exporting on one or more phases and importing on the others.

I have a superb piece of kit for monitoring our supply (an IoTaWatt for those that are interested) - which samples about 15 times per second per channel. Each device has 14 channels (3 phases uses 3 Channels, one Current Transformer on each) so have a good handle on what is happening to our supply, generation and consumption in much greater detail than I expect a smart meter to report.

When we had the EV charger installed the fuse of each phase was increased from 60A to 80A - at the time they weren't fitting 100A fuses for 3-phase domestic premises - but that shouldn't affect me as I am highly unlikely to draw that amount of current (or able to afford it if I did).

I have booked the Smart Meter installation.

Having done the analysis (thank you, IoTaWatt) the E.ON Next EV tariff makes sense for my house.

It also looks like splitting my Feed in Tariff into Generation and Export and giving up the export (6.9 pence on 50% of Generation) for the Smart Export Guarantee rate that E.On pay (16.5 pence on ACTUAL export) is worth considering. The risk, of course, being that the SEG rates drop below the FiT rates at some point in the future or I consume even more of my self generation than I do at present.