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Cofy

Energy cost

energy-cost is an open-source Python library that calculates a complete energy bill from metered consumption and injection. It’s what Cofy’s billing module and energy_cost source use, and it also works on its own.

A bill is calculated from a contract, which brings together:

Part What it is
supplier The energy supplier’s tariff
distributor The grid operator’s tariff
fees Government fees and levies, such as excise
taxes VAT on each part of the bill
timezone The time zone all dates and times are read in

You rarely write all of it. Give a contract a region, connection type, customer type and distributor, and energy-cost fills in the distributor’s tariff, the fees, the taxes and the time zone from its built-in data. Then you only write the supplier’s tariff:

region: be_flanders
connection_type: electricity
customer_type: residential
distributor_key: fluvius_imewo
supplier:
  - start: 2025-01-01T00:00:00+01:00
    consumption:
      energy: { constant_cost: 95.0 }

Where to go next

Section titled “Where to go next”
  • Contracts: every part of a contract, and how built-in data is filled in.
  • Tariffs: how to write a tariff, from a fixed price to time-of-use, tiers and dynamic prices.
  • Taxes and capacity: VAT rates and capacity tariffs.
  • Built-in data: the regions, distributors, fees and taxes energy-cost knows.
  • Examples: complete contracts to start from.
  • Using it from Python: calculate a bill in your own code.

Units

Section titled “Units”

energy-cost works in euro, MWh and MW:

Quantity Unit
Energy prices €/MWh. 1 c/kWh is 10 €/MWh, so 9.5 c/kWh is 95.0.
Fixed costs € per period, such as € per year
Capacity prices € per MW
Tax rates A fraction: 6% is 0.06
The bill €

A positive cost is paid by the customer; a negative cost is received. That holds for injection too: a price you pay for the energy you inject is positive, and a price you receive for it is negative.

Inside Cofy

Section titled “Inside Cofy”