Economy 7 Cylinder Explained

Economy 7 Cylinders are hot water cylinders are designed specifically to work with the cheaper rate Economy 7 Tariff, or Maxistore 7 as it is sometimes referred to.

The cylinders feature two immersion heaters which are located at different heights in the cylinder and programmed to work at different times of the day.

The immersion which works with the Economy 7 tariff, is located at the bottom of the cylinder and is automatically activated when the cheap rate electricity is available, heating the entire contents of the cylinder.

The second immersion heater tends to be located in the top third of the cylinder, allowing the householder to boost the hot water, heating a small amount of hot water to meet the short-term demand in the most cost effective manner.

To ensure the Economy 7 Cylinder can retain the heat over the course of the day, the cylinders should feature a minimum of 50mm high quality insulation.

Economy 7 Cylinder Sizing Guide
Depending on the project requirements, we tend to recommend opting for a slightly larger size of cylinder on an Economy 7 tariff. This maximises the amount of hot water that can be stored with the cheaper tariff and then used throughout the day.

So for example, where you would normally specify a 120 litre cylinder for a 1 bedroom apartment, we would recommend increase the sizing on the cylinder to 144 litres.

Vented Economy 7 Cylinders
Whilst most Economy 7 cylinders tend to be specified as Direct Vented Cylinders, Indirect Economy 7 Cylinders may be required from time to time when the householder is looking to incorporate a back boiler or solid fuel source such as a wood burning stove.

THERMflow Economy 7 Thermal Stores
Our THERMflow Electric Thermal Stores can be customised to incorporate two immersion heaters as per the Economy 7 specification to enable the householder to take advantage of the cheaper tariff. Click here to find out more about our THERMflow thermal store

CUBEflow Economy 7 Rectangular Electric Thermal Store
Our CUBEflow Electric Thermal Store features two immersion heaters as standard, one of which can be set up to work with the Economy 7 tariff.

POWERflow Economy 7 Unvented Cylinder
Whilst its unlikely to specify an unvented Economy 7 cylinder on a project, our market leading POWERflow Unvented Cylinder can also be customised to incorporate two immersion heaters.

Key Features to Consider When Choosing an Economy 7 Cylinder

  • Size of Cylinder
  • Optimum positioning of immersion heaters
  • Quality of insulation – should be a minimum of 50mm
  • Standing Heat Loss
  • ERP Rating

Economy 7 Explained
The Economy 7 Tariff enables householders to enjoy 7 hours of cheaper, off peak energy during the night, with the actual time varies from region to region and per supplier. Click here for more details on timings.

There are also other energy tariffs, such as Economy 10 and Economy 2000, which offer similar cheaper tariffs which relate to the time of use, however fewer suppliers are providing these options.

These tariffs are designed to help householders to save money on their energy bills however advice must be taken to ensure the tariff is right for you.

According to Money Saving Expert, Martin Lewis, the general rule of thumb is the tarrif is really only suitable for those people which have storage heaters, user hot water tanks and who use 40% of their electricity at night. See more at