Maximizing Electricity Savings via Economy 7


Understanding Economy 7

Economy 7, a differential electricity tariff or ‘multi-tariff rate,’ is a type of energy tariff that can be utilized as a cheaper alternative to paying a standard rate on electricity, depending on your lifestyle and energy habits. Economy 7 offers cheaper electricity during specific hours of the night, with a higher rate applying to electricity drawn during the day. Generally, you’ll get cheaper rates between midnight and 7am. Octopus Energy, however, is well known for supplying electricity from 100% renewable sources and offers an incredibly low rate of 5p/kWh during the hours of 00:30 - 4:30.

If you use more energy after midnight, you could save money by switching to an Economy 7 tariff. That being said, it may not suit you if most of your household energy is used during the day, as you’ll be charged more on the higher rate - unless, of course, you can store cheap electricity drawn at night to use during the daylight hours when you actually use most of your electricity. 

How to maximise Economy 7

Energy prices are at an all time high and are likely to continue to increase. With the right battery storage system, it's possible for a household to store enough electricity to supply the full demand of the property.   A typical low voltage battery storage system such as Pylontech with a Solis or SoFar AC charger will charge and discharge at 3kW, meaning 12kWh can be stored during the 4 hrs of Octopus Go’s low rate. This can meet the demand of a broad range standard household appliances using up to a maximum combined demand of 3kW.

With a higher voltage system such as SolaX or Fox, it’s possible to charge and discharge at a rate of 6kW/hr, translating to 24kWh can be stored during the 4 hrs. For hybrid AC/DC systems, it is also possible to have multiple hybrids using SolaX to potentially meet the demand of any household appliances, even high-demand appliances such as air source heat pumps (ASHPs), electric vehicles, swimming pool heaters, jacuzzis etc.

Understanding which battery storage system is right for you

Two key factors to take into consideration when selecting the battery storage system are the storage capacity you need and your peak demand.

The advisable storage capacity can be calculated by looking at your total usage over a 24hr period, and determining how much of this amount you wish to store from the Economy 7 off-peak rate. Over-sizing will mean that more capital will be invested than required, but can allow for increased draw rate and longer usage in the future. Under-sizing usually results in lost potential savings, but maximises the capital invested.

Peak demand is the maximum electricity demand at any given time of the day. It is important to know your peak demand, as a system that cannot supply this demand may mean you still need to draw significant amounts of electricity from the grid during costly peak-rate hours. For example, if you regularly have 6kW of high demand appliances running, and you only have a battery system that can discharge at 3kW, you will still require 3kW from the grid. Whereas If you have a system that can discharge at 6kW then you will meet your peak demand without needing to draw from the grid.

Battery storage key facts comparison – AC battery storage systems


Battery system

Charge/

Discharge rate 

Maximum Capacity

Typical Battery cost/kWh

Typical Kit cost/kWh

EPS function

Depth of Discharge

Alpha

3kW

17.4kWh

£287

£338

Yes

96%

Fox

5kW

18.2kWh

£276

£308

Yes

90%

Givenergy (x3 chargers)

9kW

120kWh

£276

£304

Yes

100%

SoFar / Pylontech

3kW

14.4kWh

£254

£300

Yes

90%

Solis / Pylontech (x3 chargers)

9kW

63kWh

£242

£265

Yes

90%

SolaX

6kW

18.9kWh

£287

£365

Yes

90%


Hybrid battery storage systems

Battery system

Charge/

Discharge rate

Maximum Capacity

Typical Battery cost/kWh

Typical Kit cost/kWh

EPS function

Depth of Discharge

Alpha 

5.0kW

60.6kWh

240

267

Yes

96%

GivEnergy 3.6 

3.6kW

41kWh

271

297

Yes

100%

GivEnergy 5.0

5.0kW

41kWh

271

299

Yes

100%

Fox 3.7

3.7kW

18.2kWh

276

322

Yes

98%

Fox 5.0

5.0kW

18.2kWh

276

323

Yes

98%

SoFar 3.0

3.0kW

14kWh

255

313

Yes

95%

SoFar 3.6

3.0kW

14kWh

255

316

Yes

95%

SoFar 5.0

3.0kW

14kWh

255

319

Yes

95%

SoFar 6.0

3.0kW

14kWh

255

322

Yes

95%

SolaX 3.0

3.0kW

18.9kWh

312

363

Yes

90%

SolaX 3.7

3.7kW

18.9kWh

312

366

Yes

90%

SolaX 5.0

5.0kW

18.9kWh

312

372

Yes

90%

SolaX 8.0 3-phase

(10 x inverters)

80.0kW

252kWh

306

379

Yes

90%

SolaX 10.0 3-phase

(10 x inverters)

100.0kW

252kWh

306

383

Yes

90%

Solis 3.0

3.0kW

96kWh

255

268

Yes

95%

Solis 3.6

3.6kW

96kWh

255

268

Yes

95%

Solis 4.6

4.6kW

96kWh

255

268

Yes

95%

Solis 5.0

5.0kW

96kWh

255

269

Yes

95%

Solis 6

5.6kW

96kWh

255

269

Yes

95%

Sunsynk 3.6

(10 x inverters)

36kW

153.6kWh

256

292

Yes

100%

Sunsynk 5.0

(10 x inverters)

50kW

153.6kWh

256

295

Yes

100%

Sunsynk 8.0

(10 x inverters)

80kW

153.6kWh

256

316

Yes

100%


All prices for illustrative purposes only and based on the maximum size system accurate at the time of calculation, prices without VAT.

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