Risk of power cuts in the UK: Should you protect your home?

Why do power outages happen?

Power cuts can occur due to a multitude of reasons and originate from different components of the transmission system (lines, substations, transformers, power stations etc.). The three most common causes for blackouts are weather, grid instability and equipment failure. A weather-related incident is for instance when a storm causes a tree to fall on an overhead power line. Grid instability is when demand and supply do not materialise as predicted, leading to an imbalance between supply and demand, and ultimately causing a frequency or voltage deviation in the grid. Lastly, equipment failure occurs simply when pieces of equipment, such as transformers or substations, break down.

How common are power cuts in the UK?

Power cuts happen but are relatively uncommon in the UK, especially compared to the developing world. For instance, at the moment of writing, in UK Power Networks (one of 6 UK distribution operators), 17 unplanned power cuts across 44 post codes were happening (see here). This represents about 0.0026% of the UK’s 1.7 million post codes.

However, while they are rare, they can be grave. A big recent event was storm Arwen in November 2021. With wind speeds of up to 98 Mph, the storm damaged several major power lines. As a result, about 1 million customers lost power. For about 180,000 customers, the outage lasted more than 24 hours. 40,000 customers remained without supply for more than three days and 4,000 customers for over a week. Call centre wait times were up to 6 hours.

Will power outages become more common?

It is notoriously difficult to predict the future, however there are two key reasons why power cuts may become more common.

First, the energy transition makes it harder to balance the grid, that is, keeping supply and demand in balance at any point in time. This is because most renewables are “intermittent”, meaning they cannot be easily turned on or off as a more traditional coal or gas power plant would. Instead, sun and wind determine generation potential. At the same time, peak electricity demand is increasing massively as a result of electrification in different areas of life such as transport (EVs) or heating (heat pumps).

This difficulty becomes evident when looking at the rise of “frequency events” in the transmission grid. The UK grid operator is aiming to operate the grid at a frequency of 50 Hz at any point in time. This is because UK appliances are designed to work at 50 Hz. Prolonged deviations significantly above or below 50 Hz mean appliances won’t work or they be damaged. There is an operational limit of +/-0.2 Hz and a “statutory limit” of +/- 0.5 Hz. That means, the grid operator is required to keep frequency within a band of 49.5-50.5 Hz and seeks to keep it between 49.8Hz and 50.2Hz at all times by balancing supply and demand. Every time this limit is exceeded is called a “frequency event”. As Figure 1 shows, such events have increased markedly in recent years. This is because the already tricky job of keeping supply and demand in balance has become even trickier as a result of the rise of intermittent renewables and more high-powered electricity consumers.

Not every frequency event leads to an outage, but every additional event carries the risk of a power cut. For example, the spike in frequency events in December 2023 is attributable to a fault in the inter-connector between the UK and France. Even though the frequency dropped to just 49.27 Hz, the national grid’s control rooms reacted extremely quickly and avoided a blackout by dispatching additional generation capacity. However, that such capacities were available at sufficient capacity at this point in time cannot be taken for granted.

Second, it is commonly held that severe weather events will become more frequent as a result of climate change. According to the Met office, the most recent decade has seen a significant increase in extreme weather events. For instance, there has been a 320% increase in major UK storms from 2010-15 (10 storms) to 2015-20 (42 storms). The Met office attributes this to the effects of climate change. Extreme weather events are one of the most common causes of power cuts. For instance, fallen trees that couldn’t resist a storm often fall on overhead power lines, cutting through the cables.

How a backup battery can protect you against power cuts

The best way to protect yourself from power cuts is through a smartly managed home battery. An average home can be powered from an average-sized home battery for 1-2 days, which is enough time in most case before electricity can be restored after an outage. Note however, that this requires:

1. The system to be installed in a way that allows you to decouple entirely from the grid and power the home from the battery. This is possible for many state-of-the-art batteries on the market, such as the InstaGen or Powerwall battery, but requires some additional equipment and wiring.
2. The battery to be smartly managed and fully charged before an outage, based on predicting severe weather. We are working on including this feature in our [Capture AI] soon.

This makes your power supply more resilient and fit for a future with a higher risk of power outages. We can help you design, install and manage a home battery with a backup function.