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Web application for checking UK electricity and gas bills

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A web application for checking UK electricity and gas bills for organizations with a large number of supplies and / or high consumption.



Chellow is released under the GPL v3.


Chellow is a web application for checking UK electricity and gas bills. It's designed for organizations with high electricity consumption. The software is hosted at

Build Status


Chellow is a Python web application that uses the PostgreSQL database. To install Chellow, follow these steps:

  • Install PostgreSQL 12
    • Set the PostgreSQL time zone to 'UTC'.
  • Create a PostgreSQL database: createdb --encoding=UTF8 chellow
  • Set up the following environment variables to configure Chellow:
Name Default Description
PGUSER postgres Postgres user name
PGPASSWORD postgres Postgres password
PGHOST localhost Postgres host name
PGPORT 5432 Postgres port
PGDATABASE chellow Postgres database name

In bash an environment variable can be set by doing:

export PGUSER=postgres

in Windows an environment variable can be set by doing:

set PGUSER=postgres

  • Install Python 3.9 (tested on the CPython 3.9.8 interpreter)
  • Create a virtual environment: python3 -m venv venv
  • Activate the virtual environment: source venv/bin/activate
  • Install Chellow: pip install chellow
  • Start Chellow:waitress-serve --host= --port=8080 --call chellow:create_app
  • You should now be able to visit http://localhost:8080/ in a browser. You should be prompted to enter a username and password. Enter the admin user name and the password admin, and then the home page should appear. Change the admin password from the users page.

Manually Upgrading Chellow

To upgrade to the latest version of Chellow do: pip install --upgrade chellow

Automatically Upgrading Chellow

The bash script will check for a new version of Chellow and if one's there it will stop Chellow, then do the upgrade, then start Chellow.

Using with systemd

Copy the following files into the /etc/systemd/system directory:

and modify them as appropriate. The chellow_upgrader.service uses the script above. The you should be able to use the following commands:

  • Start Chellow: sudo systemctl start chellow
  • Make Chellow run on startup: sudo systemctl enable chellow
  • Start the Chellow Upgrader: sudo systemctl start chellow_upgrader.timer
  • Make Chellow Upgrader run on startup: sudo systemctl enable chellow_upgrader.timer

Using A Different Webserver

Chellow comes bundled with the Waitress webserver, but the is also a Python WSGI web application so Chellow can be used with any WSGI compliant application server, eg Gunicorn. The WSGI app that should be specified is

Getting Started

This is a brief guide to setting things up after you've installed Chellow. It assumes that you have a basic knowledge of UK electricity billing. It goes through the steps of adding a half-hourly (HH) metered supply, and producing virtual bills for it, and then importing an actual bill and running a bill check.

Chellow can handle non-half-hourly supplies as well as half-hourly, and it can also deal with gas supplies, but we'll use a half-hourly electricity supply for this example.

View the Chellow home page

Assuming you've installed Chellow correctly, you should be able to open your browser, type in the URL of the Chellow application, and see the Chellow home page.


Before any users are added, if you access Chellow from localhost you'll have read / write access. Once users are added, you have to log in as one of those users. Users are added from the 'users' page.

Importing Market Domain Data

Follow the instructions at /e/mdd_imports to import the Market Domain Data into Chellow.

Add HHDC Contracts

Every supply must a have a data collector. Add in a new HHDC by going to the 'HHDC Contracts' page and then clicking on the 'Add' link.

Add MOP Contracts

Every supply must a have a meter operator. Add in a new MOP by going to the 'MOP Contracts' page and then clicking on the 'Add' link. For now just put in a simple virtual bill for the MOP, so in the 'script' field enter:

    from chellow.utils import reduce_bill_hhs

    def virtual_bill_titles():
        return ['net-gbp']    

    def virtual_bill(data_source):
        for hh in data_source.hh_data:
	bill_hh = data_source.mop_bill_hhs[hh['start-date']]
            if hh['utc-is-month-end']:
                bill_hh['net-gbp'] = 10
        data_source.mop_bill = reduce_bills_hh(data_source.mop_bill_hhs)

Add Supplier Contracts

Click on the 'supplier contracts' link and then fill out the 'Add a contract' form. For the Charge Script field enter:

    from chellow.utils import reduce_bill_hhs

    def virtual_bill_titles():
        return ['net-gbp', 'day-kwh', 'day-gbp', 'night-kwh', 'night-gbp']    
    def virtual_bill(data_source):
        bill = data_source.supplier_bill 
        for hh in data_source.hh_data:
						bill_hh = data_source.supplier_bill_hhs[hh['start-date']]
            if 0 < hh['utc-decimal-hour'] < 8:
                bill_hh['night-kwh'] = hh['msp-kwh']
                bill_hh['night-gbp'] = hh['msp-kwh'] * 0.05
                bill_hh['day-kwh'] = hh['msp-kwh']
                bill_hh['day-gbp'] = hh['msp-kwh'] * 0.1
		bill_hh['net-gbp'] = sum(
		v for k, v in bill_hh.items() if k[-4:] == '-gbp')

		data_source.supplier_bill = reduce_bill_hhs(

This will generate a simple virtual bill based on a day / night tariff. Supplier contract scripts can be much more sophisticated than this, including DUoS, TNUoS, BSUoS, RO and many other standard charges. These will be addressed later on in this guide.

Also, don't worry about the 'properties' field for now.

Add a Site

Go to the 'sites' link on the home page, and click 'add'. Fill out the form and create the site.

Add a Supply

To add a supply to a site, go to the site's page and click on 'edit'. Half-way down the page there's an 'Insert an electricity supply' form. For a standard electricity supply the 'source' is 'net'. Make sure the profile class (PC) is '00' to indicate to Chellow that it's a half-hourly metered supply. The SSC field is left blank for a half-hourly as they don't have an SSC.

A supply is formed from a series of eras. Each era has different characteristics to capture the history of a supply.

Run a Virtual Bill

At this stage it should be possible to run a virtual bill for the supply you've added. Go to the supply's page and click on the 'Supplier Virtual Bill' link. That should return a page showing the virtual bill for the supply.

Of course, the consumption will be zero because we haven't added in any half-hourly data yet.

Add Some HH Data

On the page of the supply you've created, you'll see that there's a 'channels' link, with an 'add' link next to it. Add an active import channel for the half-hourly data to be attached to.

Back on the supply page a link to the channel you just created will have appeared. Click on this and fill out the form for adding a half-hour of data.

If you then re-run the virtual bill for the period in which you added the half-hour, it should show up in the virtual bill.

It's tedious to add HH data one by one, so if you go to the page of the HHDC contract that you've created, you'll see a 'HH Data Imports' link. Click on this and there's a form for uploading HH data in bulk in a variety of formats. Chellow can also be set up to import files automatically from an FTP server.

Virtual Bills For A Contract

To see the virtual bills for a supplier contract, go to the contract page and follow the Virtual Bills link.

Data Structure

  • Site
  • Supply
    • Supply Era
      • Site
      • MOP Contract
      • DC Contract
      • Profile Class
      • Imp / Exp Supplier Contract
      • Imp / Exp Mpan Core
      • Imp / Exp LLFC
      • Imp / Exp Supply Capacity
      • Imp / Exp Channels
        • HH Data
  • Supplier Contracts (Same for DC and MOP)
    • Rate Scripts
    • Batches
      • Bills
        • Supply
        • Register Reads
  • DNOs (Distribution Network Operators)
    • LLFCs (Line Loss Factor Classes)

General Imports

The menu has a link called 'General Import' which take you to a page for doing bulk insert / update / delete operations on Chellow data (eg. Sites, Supplies, LLFCs etc.) using a CSV file.

Common Tasks

Merging Two Supplies

Say there are two supplies A and B, and you want to end up with just A. The steps are:

  1. Back up the data by taking a snapshot of the database.
  2. Check that A and B have the same header data (LLFC, MTC etc).
  3. See if there are any overlapping channels, eg. do both A and B have import kVArh? If there are, then decide which one is going to be kept.
  4. Load the hh data for the required channels from the backup file. First take a copy of the file, then edit out the data you don't want, then further edit the file so that it loads into the new supply.
  5. Delete supply B.

Local Reports

Core reports come with Chellow, but it's possible for users to create custom reports. Reports are written in Python, and often use a Jinja2 template. You can display a link to a report of user reports by adding the local_reports_id to the configuration non-core contract.

Default users

Default users can be automatically assigned to requests from certain IP addresses. To associate an IP address to a user, go to the non-core contract configuration and add a line to the 'properties' field similar to the following:

    'ips': {'': 'implicit-user@localhost'}

Note that multiple IP addresses can be mapped to the same user.

It's also possible to use Microsoft Active Directory to authenticate users with a reverse proxy server. Edit the configuration non-core contract and add something like:

    "ad_authentication": {
      "default_user": "",
      "on": true

Design Decisions

Why don't you use the +/- infinity values for timestamps? The problem is that it's not clear how this would translate into Python. So we currently use null for infinity, which naturally translates into None in Python.