Understand the natural gas bill

With the liberalization of the natural gas market in 2010, all consumers in mainland Portugal can freely choose their supplier. Because an informed choice can contribute to reducing the gas bill by 10%, by switching to a better tariff.

According to the Energy Services Regulatory Authority (ERSE), 97% of the global consumption of natural gas is from customers in the liberalized market, representing 1.18 million consumers. Currently, the free market for natural gas has 9 suppliers with only natural gas offers and 7 suppliers that offer aggregate tariffs for electricity and natural gas.

All information on tariffs is available on this portal and, in a simple and quick way, the consumer can subscribe to the tariff that allows him to save more, by filling in his data.

After this request, the retailer contacts the customer to finalize and handle the entire change process. This change has no associated cost and there is no need to modify the installation or the meter.

Natural gas invoice terms

Energy consumption

The reading of the natural gas meter is done in m3, but to be billed, consumption is converted to kWh, as is the case for electricity. For this purpose, the consumption in m3 is multiplied by the volume and pressure correction factor (FCV) depending on the region where the installation is located and between the upper calorific value (PCS), measured by the transmission system operator .

Consumption kWh (1 122) = Consumption m3 (100) x FCV (0,96759000) x PCS (11,598418)

Example: A monthly consumption of 100 m3 is equivalent to about 1 122 kWh. Therefore, for a contracted fixed unit price of € 0.0645 / kWh, there is an amount to pay for consumption of € 72.37.

Tier of natural gas

The price of this installment varies according to the contracted unit price and the step that is automatically defined according to the average annual consumption (step 1, 2, 3 or 4).

1Até 220
2221 a 500
3501 a 1 000
41 001 a 10 000

To calculate this installment, the number of days in the period to be invoiced is multiplied by the contracted unit value.
Example: For a fixed-term monthly invoice of € 0.0687 / day and tier 1, the customer pays € 2.06.

Additional services (optional)

The customer can subscribe to additional services on his energy bill, and there is normally an associated loyalty of 12 months. For example, you can have a natural gas maintenance service or gas assistance. These services ensure a discount on the amount payable for the consumption of natural gas.
Example: For an additional service the customer can pay € 9 per month.

Refunds (optional)

Some merchants refund a percentage of the invoice amount. This amount can be deducted directly from the amount payable or made available on discount cards.

Example: A 6% discount on the total amount of an invoice of € 70 / month, is equivalent to a refund of € 4.20 / month.

Fees and taxes are mandatory and applied by traders through the invoices issued:


Taxa de Ocupação de Subsolo – TOS

Corresponds to the rate of use and use of the public and private municipal domain. The value is defined annually by each municipality, so it will have different values ​​for each region. This rate consists of two terms – a variable term applied to the consumption of natural gas (kWh) and a fixed term applied to the number of days in the period to be invoiced.

Example: In the event that the place of consumption is, for example, Aveiro, the fixed term is € 0.00303380 / day, for which € 0.09 is paid per month. To this term, a variable term of € 0.00260617 / kWh is added, for which a monthly consumption of 1122 kWh is paid € 2.92.

Excise tax on natural gas fuel – IECGN or ISEP

It is included in the subcategory of tax on petroleum and energy products (ISP) with a value of 0.002412 € / kWh.
Example: For a monthly consumption of 1 122 kWh, € 2.70 is paid.

To all these installments is added the Value Added Tax (IVA) at 23%.


In short, when choosing a tariff, you must take into account the unit cost of the contracted energy terms (€ / kWh) and step (€ / day), the existence of additional services and any refunds. When consulting the tariff area for available offers or when carrying out a  simulation, you can directly subscribe to the most advantageous tariff.

Additional note: In the case of domestic installations over 20 years old and which have not been remodeled, gas inspections must be carried out every 5 years.

1. Carry out a SIMULAtion

and check the savings you can obtain by changing the tariff. You can subscribe to the new tariff on the portal, quickly and simply;

(There is no limit to the number of supplier changes and there is no interruption in the supply of natural gas)

2. Consult and compare all the TARIFfs

offers, with updated information with the possibility of filtering the contracting, billing and payment options;

3. Reduce consumption by adopting energy efficiency measures, such as our heater tip;

4. Through our support line 211 160500, your questions can be answered.

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