@korwraith Perhaps their mantra is ‘Hours is not to reason why’ . Toodles.

@korwraith very interesting. Thanks for the update.

@korwraith - please expand on the comment about EDF circumventing the Randomised Offset to the Tariff Table 'in the same way as Octopus'.

I'm not aware that Octopus has 'circumvented' the Randomised Offset, merely that their internal billing system (Kraken) has demonstrated a lower level of billing error than EDF did with your particular account.

My analysis of the correspondence between you and EDF suggested that they had tried using two internal registers with the Electricity Smart Meter Equipment (ESME) as a 'fudge'. However, in your case that fudge factor had operated in the opposite direction to that which they'd intended. It amplified the Randomised Offset error to a much greater extent.

Without further evidence we have no idea what their fudge factor did for other users.
I'm wary of drawing conclusions whilst the investigation is based on only two major foundations:

• the theoretical mathematical modelling undertaken by Simon & I
• the actual calculated billing error which EDF have admitted to in your case

I don't think that Announcement you've just published from EDF about them changing the hours during which your cheap rate is valid is related to the Incorrect Billing error.

In fact I think it will make matters more difficult for them, because they've moved too close to midnight!

At some point after 00:00:01 every ESME will start a new tariff period.
That's when the Smart Meter loads a reading into the final (48th) slot of the previous day's consumption figures.
The latest point in time when that 48th slot could be completed is 00:29:59. That's defined in the Smart Meter specification.

Unconnected to that issue, at some point after 00:00 the gas meter (GSME) will wake up, exchange pleasantries with your Communications Hub and transfer the 48th gas consumption reading of the previous day to the 'virtual GSME' in the Hub.

The transfer takes a finite amount of time, depending on how weak is the Zigbee network between the two devices. The GSME then goes to sleep for another 1800-secs. So the time period between each GSME wake-up will gradually creep forward by 1 or 2 seconds.

The GSME also has a Randomised Offset to the Tariff Table, despite that fact that we are currently charged the same for gas, whenever we use it.

In the worst case there will be a customer with a GSME Randomised Offset of 1799-secs and a GSME wake-cycle of 1802-secs.

The less time that has elapsed after midnight before your Energy Supplier sends the "Read Usage Registers" command to your meter, the greater is the likelihood that your ESME and GSME will not yet have switched across from the 48th/final period of the previous day.

When I was with OVO four years ago, I compared the gas consumption readings which they used for billing purposes against the same readings obtained by the Bright App from Hildebrand.

OVO was so fast in retrieving readings soon after midnight that their customers' gas usage pattern was shifted one 30-min period forward in time.

On the graph above you will see the first (left-most) gas consumption reading, as declared by OVO, was actually the 48th period of the previous day.

That was a crucial piece of evidence which allowed Simon and I to confirm that the Randomised Offsets stipulated in the Smart Meter specification, were indeed being implemented by the meter manufacturers.

Posted by: @transparent

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@korwraith - please expand on the comment about EDF circumventing the Randomised Offset to the Tariff Table 'in the same way as Octopus'.

EDF said their future billing system wouldn't suffer from the same 'doesn't start exactly on the hour' issue, so I'm assuming this email is indicative that this new system is now in place (although who can be sure of anything they say?).

In any case, as far as I can tell, Octopus billed me perfectly. My off-peak period started at midnight, my usage spiked at midnight, my bill reflected this as expected, without any leakage into the adjacent periods. Indeed, Octopus' bills identically detailed the same 30 minute UTC usage data that I downloaded from my smart meter. None of this peak / off-peak 24 hour counter stuff that didn't actually align with the advertised off-peak times that EDF's system was based on (presumably because of the random offset).

My non-expert understanding (that may very well be incorrect) is that in my manually controlled case, the Octopus approach to billing is perfectly adequate, from a consumer point of view. However, smart devices that co-ordinate with the randomised off-set clock in the smart meter would presumably still have issues as we're now billing purely by UTC time and disregarding local offsets. By ignoring the random offset it discourages devices to be synced to the random offset clock and so does away with the intended feature of the random offset, which is to improve grid stability. 

At least, that's my non-expert take. Please correct any misinformation 😀 

Posted by: @transparent

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Please keep adjusting the time at which you start drawing 'cheap rate' electricity @korwraith 
It seems that you have a meter where the Randomised Offset to the Tariff table is particularly large, and therefore easier to work out.

I've had a further bill issued since, covering mid June to mid July. 

The data from my meter indicates:

512.9kWh off peak
8.85kWh peak
(521.75kWh combined, 98.3% off peak)

EDF Billing for the period:

512.89kWh off peak
9.33kWh peak

(522.22kWh combined, 98.2% off peak)

I can't say what time of day EDF polled the counters at so for all intents and purposes I consider this to be a match BUT ONLY BECAUSE I MANUALLY ADJUSTED FOR MY METER'S RANDOM OFFSET.

My battery inverter and car charger were set to charge at 15 minutes AFTER the supposed start of my off peak period at the time (i.e. 01:15). My previous bill on page 4 of this thread had these devices set to charge 10 minutes after the start of off peak period (01:10).

Therefore I conclude my randomised offset to be between 10 and 15 minutes, likely closer to the latter than the former. Once I've another bill and more information regarding EDF's potential change to their billing system I will possibly experiment with moving my device charging times to 5 minutes passed the stated start of the off peak period.