EmonPi for Cohousing project?

I’m involved in ChaCo, a cohousing project in Leeds scheduled for completion in summer 2019. I was alerted to your EmonPi product by people from the Carbon Coop and proceeded, via Leeds Community Energy to install my own EmonPi. As documented on Twitter I was very impressed with the results, which I’ve made available to the world, and more importantly my house mates, via a live feed (thanks for the feedback - finally I’m taking up your suggestion of asking questions on your excellent forum).

The question is: what would you recommend for logging the electricity use and PV production for a medium sized (30 house) co-housing project in which we are the energy supplier to households via a private wire? This is a broad question I know but it can be broken-down:

  1. Can EmonPi legally be used for billing?
  2. What are the relative strengths of replacing vs working parallel with a standard meter?
  3. If we go with an EmonPi-type set-up with 10 second readings how would you recommend setting-up a project-wide database of houses for ‘autobilling’ purposes?

Many thanks for an amazing product, good documentation and seemingly a slick community forum.

Hello @Robinlovelace and welcome to the forum, great to hear of your introduction from CarbonCoop @beaylott and @cagabi from carbon coop are on the forums here too and may be able to give you some more detailed advice on what your after.

The EmonPi is not designed for billing applications, it neither meets the accuracy requriements nor does it have the required certification and approval. The same goes for emoncms, it is not designed for billing and its not something I have any experience of doing unfortunately.

There is some information here about meter approval requirements that might be useful.

I imagine the solution would involve a combination of a MID certified meter per tenant such as an elster A100C: http://www.rayleigh.com/elster-a100c-mid-certified-single-phase-class-1-solar-generation-meter.html
which you could then automatically read the kwh figure from using a meter interface such as the Irda port. Its possible to read from this meter with our optical pulse reader (used in irda mode), an emontx and the elster meter reader firmware.

@beaylott do you have any other suggestions?

Many thanks for the quick-fire reply and the links. We’ll discuss this and get back to you. Any further information about the options / recommendations that are most future-proof very welcome. And any ideas about people / organisations that could help with the set-up a bonus.

One idea I had was an ‘energy dashboard’ in the common house that could log both electricity generation and use. I imagine the same system used for the ‘autobilling’ could generate that. Another bonus would be per house private feeds that interested householders could use to monitor their energy use on-line. Sure that must be possible in this day and age and that the links you provided will help guide us in the right direction.

Hi Robin , I believe you have contacted Carbon Co-op separately and I will reply to your there as well, but just to confirm what Trystan said if you are doing sub-metering (i.e. you are using that information for billing purposes) you need a MID meter. However, you have quite a lot to choose from. For your use case (with 30 homes) you need to think about what the cost per unit is going to be and how you are going to get the data from the meters back to the local server/internet. I would also say it is important to get this right as it is much easier and cheaper to specify this now. You want something which is interoperable and will provide good quality data at a high enough resolution. We have seen a few projects where they got this wrong and are regretting it now because they either have to replace everything at great expense or jury rig an expensive solution to make it work.

One solution would be a wired solution with Modbus meters which can be cheaply daisy chained together into a few gateways which will provide the measures to a server using ModbusTCP. This is a pretty typical old school setup for energy management and works fairly well for the number of meters you might have (<40). There is a range of suitable Modbus meters available. Alternatively you could connect each one to a emonPi (although in this case emonPi hardware maybe overkill as you just need USB) - although then you have to think about how you will manage ~30 of these and get the data out of them (if you are installing wired internet across the site this may be as simple as putting an ethernet point next to the meters). Another solution would be to look at meters with an integrated radio solution, probably Zigbee mesh. Be careful though as many radio solutions do not work well (Wireless MBus seems to be particularly popular amongst meter manufacturers but is rubbish in our experience).

I would avoid using SMETS-compatible smart meters (as they are not really intended for your use case and introduce all sorts of complications and costs) or doing anything over pulse or optical interfaces as they are less reliable/accurate and the overall cost is going to be higher (even if the meters themselves are slightly cheaper).

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Many thanks Ben. I agree with all the objectives you set-out and it sounds like there are options. We are at the point of appointing a contractor so imagine it’s something we should talk to them about. An advantage of the EmonPi-like idea is it’s future-proofing ability to add any number of feeds, e.g. for temperature etc, in the future.

But understand the need for a certified monitor and that means MID. Any experience others have very useful, in addition to the experience Ben outlines.

Hi @TrystanLea and @beaylott just an update our end, due to various factors the build is unlikely to be completed until early 2021 at the earliest. The good news is that it is actually (finally!) being built now: http://chapeltowncohousing.org.uk/

We still have not decided on how we will do ‘autobilling’ to charge residents for electricity usage but we certainly will need to do so because we will buy the electricity in bulk via a private wire, so it’s all to play for. I therefore have a few follow-up questions:

  1. Have there been any technological/regulatory/other developments over the last 2 years (can’t believe my original post is already that old!) relevant to community-level monitoring/billing solutions?
  2. Do off-the-shelf monitoring units, such as this Orsis S2-M SmartGen Single phase electricity meter, look viable for our needs from an informed technical perspective?
  3. What software for managing electricity usage and bills are now available? There was lots of mention of meters in the great discussion above, with @beaylott outlining a range of options (not all of which I fully understand I must confess), but not much on billing software. Orsis provide a marketing brochure that has little on technical detail and lots of glossy images, wondering if this would do the trick or if there are any flaws in the system that they have described in a link below. Would be great if open source solutions are now available.

I’m taking on-board the warning to

be careful though as many radio solutions do not work well

more broadly as a system setup that does not work well could create big issues for us. Conversely an affordable and effective solution that is well documented and reproducible could make our lives easier and provide a basis for other community projects to shift towards bulk purchase of electricity and community billing, with large potential social and environmental benefits.

Here is a link to a ‘whole system’ set-up that you can buy off-the-shelf from Orsis. Any comments of +s/-s of this very welcome.

Can you upload that document here please? (For the reasons spelled out in the FAQ). I’ve increased your privileges so you should be able to do that.

My only concern with this is that orsis seem to have control of your data. You at least want the option of pointing the feeds at another server. Ideally you would aggregate them first. It is possible the radio solutions will do this as they will need a gateway to get to the internet.

As long as you can get the data out of the orsis system easily the sky is the limit. There are hundreds of billing platforms. Just make sure you dont get tied into orsis!

Well smart meters are certainly starting to come up with the goods.

I cant recall exactly when we last spoke but Ofgem are still not looking favourably on private wire. Some of the regulations stemmed from EU so will be interesting to see how this might change.

Sure, here is the file that I tried to upload previously.
Energy Management, Sub Metering and Tenant On Charging.pdf (2.1 MB)

Edit - formatted text. BT - Moderator

Thanks for the quickfire reply @beaylott, lock-in to Orsis was my concern also - will need to clarify that they can provide the feed. Is the right way to phrase this as a question to a potential subcontractor the following?:

Does your system allow control over our data, in the sense that we would be able to store the real-time data on our own server on site for maximum data security, redundancy and security? Also I would like to check what the temporal resolution of the data you provide is for each of the households. And what autobilling software would you recommend? We are hoping to support open source solutions.

I don’t know what the regs are regarding billing records, but I suppose there are some. I expect you may need to think about offsite backup arrangements, for example - what if the building containing your billing system burned down?

Locking in isnt always a problem, however when a company gets taken over or goes bankrupt that’s when the fun starts!

Commercially I’ve had systems made ‘end of life’ after a take over of the original company. Upgrades to the new system cost £10k+