This is the second part to a post I published earlier this week in which I summarised some things I learned about working with half-hourly energy data. I’ll be updating that shortly with a few extra details and clarifications.
This post will be a summary of some things I’ve learned about energy meters and metering. It’s not a comprehensive primer on meters. I am not an electrician. And I’ve already written at length about smart meters and non-domestic energy data infrastructure so will avoid covering same ground here.
If you’re already familiar with energy data and metering there’s unlikely to be a lot of deep insights here. But there are a number of things that weren’t obvious to me at the start of my journey into energy data. And some which have sprung up since to surprise me.
A site will have a single electricity, or gas or other meter
A UK home usually as a gas meter and an electricity meter. But generally working with energy data means dealing with multiple meters at a single location.
It’s not even always true that UK homes have a single electricity or gas meter. And non-domestic sites can have many different electricity and gas meters serving different parts of the property. We’ve got schools on Energy Sparks with more than 20 meters.
The SMETS2 smart meter standard supports something like five different electricity meters within the same local network.
Related to this, because an MPAN is an identifier for an electricity supply point, that identifier can at times map to multiple electricity meters, each with their own serial number. This one tripped me up recently.
The set of meters on a site won’t change
Devices fail and are replaced. Devices need to be upgraded and are changed. Replacements will have different serial numbers but the same MPAN. Except where they don’t.
Buildings grow and shrink on a temporary or permanent basis. They can be refitted and rewired. As a result, the set of meters at that location may also change.
Meters can be direct replacements for one another. Or the new meter might be monitoring part of the consumption originally reported from an existing meter(s). Or it might be measuring something new.
To build a picture of the overall energy usage at a site you need to aggregate data from multiple meters. But you will likely need some rules to define how to build that aggregate time series from the underlying data.
For example, if you’re advising someone on energy efficiency, when looking at overall usage you will want to make sure you have the latest data from all currently installed meters. You don’t necessarily want to make recommendations if you don’t have recent data for one or more meters (unless perhaps if they are monitoring a minor part of the on-site consumption). So you need some rules that handle lags in data as well as meters being removed.
The consumption from multiple meters is additive
Let’s say you have data for three electricity meters at a location. You can calculate the total consumption by just adding up the data from those meters, right? Not necessarily.
Submetering is where additional meters are installed at a location to measure a particular type of consumption (e.g. your lighting or heating) or even a piece of equipment (a heat pump, a boiler).
Submeters measure the same usage as the mains meters on the same circuit. You can’t add them all up otherwise you’ll double count.
Some solar monitoring systems will also be metering the mains electricity supply, so you may have two ways to access that data.
So you need to know what those different meters are measuring.
Different meters on the same site will have similar usage profiles
Or, to put it differently: you can’t use usage from one meter to estimate that of another.
This is obvious when you stop to think about it.
Meters may be measuring different buildings or areas of a property that are used in very different ways. Submeters might be monitoring different types of equipment with different usage profiles/.
The profile of gas usage for a kitchen is different to a boiler. In a school, the gas usage in the science block might just be measuring the gas taps in the classroom. These are all very different.
A couple of less obvious situations that have arisen in our work at Energy Sparks.
Meters are only measuring consumption by the people or organisation paying the bill
This is obviously the case for rental properties, flat shares, etc. But here’s a couple of non-obvious domestic examples.
One school on Energy Sparks has a leisure centre that operates on the same site. Its metered as part of the school’s overall consumption but is run by a different organisation. A submeter is used to do some internal recharging between the school and the leisure centre. This does mean that the school’s overall energy consumption isn’t representative of its own energy efficiency
In another situation, a new school is being built next to an existing one. Once built it will have its own meters and be part of a separate trust. The building site is temporarily using the existing school’s electricity supply until the new supply is installed. Again there is a submeter helping to handle the billing.
This makes analysing energy usage particularly challenging as usage no longer correlates to the organisation you’re supporting with your energy efficiency advice.
Meters have a consistent way to be remotely read
There are a wide range of different technologies used to allow a readings to be fetched, or sent from a meter. This includes GSM, 3G, the UK’s Smart Meter WANs, via a modem or by connecting to a local Wifi.
Older energy meters need to be upgraded or replaced before the UK’s 2G/3G networks are switched off.
Solar systems are fully metered
For solar systems you’re generally interested in how much the panels are generating, how much of that you’re consuming and how much you might be exporting.
Sometimes the generation, self-consumption and export are individually metered within the solar monitoring system. But that’s not the common case. Older systems might only have a generation meter.
The UK’s Feed-In-Tariff scheme paid people with solar panels for exporting energy to the grid. The solar generation was metered, but the export was just estimated at half the generation. So you got paid the same amount no matter how much you were exporting. So there was no need for export meters.
The is a nice example of how a policy design directly shapes (data) infrastructure and its impact on the long-term management of that infrastructure. Its left a potential gap in understanding how much the electricity being generated by these panels is actually being consumed on site, impacting the ability to give energy efficiency advice and support, e.g. local load-balancing.
The newer Smart Export Guarantee and export tariffs use export metering to monitor how much electricity you’re actually exporting. So a combination of generation and export metering is now more common.
But, as noted below, if the panels are installed under a Power Purchase Agreement and its unlikely that there will be significant export, an export meter might not be installed by the organisation (e.g. a community energy company) that owns the panels.
The lack of a self-consumption meter isn’t an issue, because self-consumption is just the amount of electricity generated minus the amount exported. Right?
Solar panels are owned by the people or organisation whose property they’re installed on.
This is no longer even true for domestic properties let alone non-domestic.
Power Purchase Agreements (PPA) allow (community) energy companies to install solar at a property then have an agreement with the owner to supply them with electricity at a discount rate. The energy company gets guaranteed revenue for the consumption, and perhaps some export revenue as well.
Tesco are installing solar on their stores this way. And the project in Cornwall I linked above illustrates that this arrangement is coming to the domestic market too.
This means that the energy from the solar panels is not free. Tariffs are set in the PPA. It also means that you may need to negotiate data access with a third-party, although transparency is usually beneficial on both signs.
Meters at the same site fail to be read in consistent ways
You have multiple types of meter at a site. They use different technologies to store and transmit readings. And those meters are managed by different organisations. That means you will encounter uneven data coverage and quality issues that means the usage reported by different meters does not align.
In my last post I mentioned that solar generation and export meters can end up producing inconsistent readings when they independently fail or fill in missing readings.
This means you sometimes cannot reliably calculate the self-consumption if its not metered and will need to find other ways to estimate that.
You might encounter similar issues with submeters.
Connectivity issues will be sorted promptly
lol, no.
Meter upgrades and replacements are carried out promptly
See above.
Non half-hourly meters don’t produce half-hourly readings
The energy industry refers to “non half-hourly” and “half-hourly” meters. Half-hourly meters are installed in locations with higher consumption and must produce half-hourly readings.
Historically non half-hourly meters were read, e.g. monthly and so did not produce half-hourly readings.
But increasingly “non half-hourly” meters include AMR and SMETS2 meters that actually do produce half-hourly data.
The terms “half-hourly” and “non half-hourly” now relate more to regulations around what meters are installed, how quickly connectivity issues need to be sorted, and how usage is settled rather than relating to the actual capabilities of the meters.
Smart Meters store actual customer tariffs
This seems to be generally true for domestic properties. When a smart meter is installed within around 24-48 hours the default tariffs on the meter will be replaced by your actual tariffs.
It’s your energy company’s responsibility to push those to the meter as they are used to provide you with cost advice for your In-Home Device. But I’ve heard of problems meaning that tariffs are not up to date.
For non-domestic usage, there isn’t always an In-Home Device provided. They’re not that helpful in a large building. And while the tariffs might be pushed to the meter, that doesn’t always seem to be the case.
Smart Meters tariffs can be used to calculate bills
I believe this is actually true for domestic meters but its not true more broadly.
Smart meters support a range of tariffs including flat rates, differential (time of use) tariffs as well as more complex tariffs. E.g. block based pricing (e.g. the price per unit is fixed until a threshold). They also support a simple standard charge.
The structure of what tariffs can be supported is part of the SMETS2 standard.
Non-domestic tariffs are way more complicated. Specifically, the daily standard charge that we have on our domestic bills is unbundled into a range of charges including:
- Agreed Supply and Excess Capacity charges
- DUoS and TNuOs charges which are basically additional differential tariffs that applied by the distribution and transmission network operators
- Standing charges
- Fixed additional fees
- Settlement agency fees
- Metering agent charges
- Site fees
- Data access fees
- etc, etc
Those can’t be stored on a smart meter. So while you might be able to access the basic consumptions costs you need additional information to calculate a bill.
Energy efficiency advice that focuses on the basic unit rate costs of consumption will underestimate those if they don’t take into account the DUoS and TNuOs charges.
None of this is openly or easily available.
The complexity of non-domestic billing, the potential for errors, opportunity for re-negotiation of fees, and ability to unbundle services like meter management, is why there are a whole class of energy brokers and reconciliation services serving that market.
There are standard APIs and formats for energy data
There are no standard formats for tabular energy data. Energy suppliers generally do not offer APIs for accessing consumption data.
Recent policy changes around access to non-domestic energy data have improved access but not standardisation; in fact formats have proliferated.
There is no standard API for accessing Smart Meter data. There is one for interfacing directly with the DCC but it’s a low level messaging system and access to it is, understandably, tightly controlled.
Services like n3rgy and Hildebrand that have created APIs to wrap that lower level Smart Meter infrastructure are all bespoke.
There are no standardised protocols for agreeing consent to access data.
Solar monitoring systems do not have standard APIs even though they frequently offer the same basic functionality. At Energy Sparks we’ve integrated with three systems initially, based on those we’ve most commonly encountered in the education sector.
If you want to get a sense of the number of solar monitoring systems, then take a look at Solar Fox, who provide display panels to show how your panels are performing. Currently they have integrations with 74 different solar monitoring systems.
While some suppliers provide access to submeter data, because these might be remotely read in different ways through different services. So there isn’t a standard way to access that data either. This includes data that might be coming from heat pumps, district heating, etc.
If future energy systems are about local generation, storage and load balancing, we need more secure, standardised APIs onto these systems.
Lost Boy 
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