National Grid's Demand Flexibility Service - First Experiences


Photo 1: Rainbow over Hereford (8th December 2023)

The Demand Flexibility Service (DFS) operated by National Grid allows residential and commercial customers to earn cash rewards by reducing their electricity usage during peak demand; usually, in the early evening period (16:00 to 19:00 hours). By reducing electricity demand during this period, expensive and polluting standby fossil fuel generators (especially oil and coal) are not required to fire up their turbines. This makes the UK electricity supply not only less carbon-intensive but also cheaper for all consumers. Started in the 2022/23, this winter will be the second trial period for this service and there will be 12 tests between November 2023 and March 2024.

To take part, you will need to have a smart meter capable of half-hourly metering (Photo 2). This is 

Photo 2: Our Smart Meter
because the test periods are multiples of 30 minutes (e.g. between 16:30 and 18:00 hours) and your electricity supplier needs to be able to measure your test period usage relative to your normal usage. In practice, householders are asked not to use high-powered appliances - such as kettles, ovens, washing machines, tumble dryers and dishwashers - during the test period. 

We are on a 100% renewable energy tariff with Good Energy and received our first invitation to participate on November 29th after first signing up to the scheme in mid-November. You have to opt in so Good Energy can set up the necessary half-hourly monitoring.

Figure 1: Invitation to Opt In to DFS Test

As noted above, the advice is to avoid using any appliances that consume lots of kWhs, charge up all your battery-operated devices (laptop, phone) beforehand and don't worry about turning off stuff on standby (e.g. TV) as this will make little or no difference. 

Figure 2: Suggestions for Reducing Power Consumption

So far, we have had three Power Pauses (as Good Energy calls them): November 29th, December 1st and December 5th). Two of the pauses were for 1½ hours and one for 1 hour between 16:30 and 18:30. Today, I received feedback on how much energy we had saved and how much money we had 'earned'

  • For the Power Pause on November 29th (17:00 to 18:30), energy saved = 0.407 kWh, and money earned = £1.63 (rebate is £4 per kWh)
  • For the Power Pause on December 1st (16:30 to 18:00), energy saved = 0.000 kWh, and money earned = £0.00
  • For the Power Pause on December 5th (17:30 to 18:30), energy saved = 0.000 kWh, and money earned = £0.00

Why did I save energy on the first Power Pause on November 29th (17:00 to 18:30) and not on the second and third Power Pauses on December 1st (16:30 to 18:00) and December 5th (17:30 to 18:30)? The reason, possibly, is down to my Air Source Heat Pump (ASHP) water and space heating system.

  • On the 29th November, indoor and outdoor temperatures were 20 ℃ and 3 ℃ respectively during the Power Pause.
  • On the 1st December, indoor and outdoor temperatures were 20 ℃ and -1/-2 ℃ respectively during the Power Pause.
  • On the 5th December, indoor and outdoor temperatures were 22 ℃ and 6 ℃ respectively during the Power Pause.
On the two December dates, the ASHP was working harder (using more electricity) due to lower outdoor temperatures (December 1st) or higher indoor temperatures (December 5th). Note: indoor and outdoor temperatures recorded on the Davis Weather Station. In future Power Pauses, I may try decreasing the room temperature setting on the ASHP system for an hour before and an hour after the set period provided it is not really cold.

It does raise some questions though. For example, when large numbers of people have converted to some form of heat pump (mainly ASHP, I suspect), will it still be possible to reduce electricity demand during peak periods? Most households currently use gas for space and water heating, making it easier to save electricity by not using energy-hungry electrical household appliances.

Is it possible to 'game the system' by maximising electrical energy usage between, say, 16:30 and 18:30 (4.30 pm to 6.30 pm) in order to set a high baseline for 'normal' usage and thus enabling larger rewards during Power Pauses? Provided daily electricity use does not increase and lead to higher electricity bills, then the energy savings (rebated at £4.00 per kWh) would greatly exceed the unit cost of electricity (£0.28 per kWh).

Does DFS make home storage batteries more cost-effective? Simply by meeting the household electricity demand from the battery only, could generate rebates of £10-20 per DFS event. Obviously, with only 12 planned events per winter in these trials, this will not pay for the battery over a reasonable time period. However, there are additional benefits to having a battery, especially if you generate your own electricity, and the number of DFS events per year may increase. Furthermore, your storage battery may be in the electric vehicle parked on your drive or in your garage using a Vehicle to Home (V2H) system.

We will be participating in future Power Pauses so I will how we get on. Expect some tinkering with the ASHP!




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