What is demand side response?
Paying electricity consumers to change when they use power — reducing at peak or increasing when there is surplus — treated as an alternative to building generation, because avoiding a megawatt of demand is equivalent to supplying one.
Why it works. The electricity system must be sized for peak demand, not average demand. Peaks are brief — a few hours on a few days a year — and building generation and network capacity for them is extremely expensive for infrastructure that sits idle almost all the time.
Shaving the peak is therefore far cheaper than meeting it, and this is the whole economic argument.
How it is delivered:
Industrial and commercial participants, which have historically been the bulk of it. Large consumers with flexible processes — cold storage, water treatment, manufacturing, on-site generation — are paid to reduce or shift load on instruction.
Aggregators combine many small participants into a block large enough to bid into markets, which is what made domestic participation possible.
Domestic flexibility, now growing substantially: time-of-use tariffs, smart EV charging, heat pump and storage heater scheduling, and home batteries. Electric vehicles are the significant development — a charging car is a large, genuinely flexible load that almost never needs to charge immediately, which makes it close to ideal.
Direct events, where consumers are asked to reduce usage during specific hours in exchange for payment, which several suppliers have run at scale.
Why it is becoming more important. As generation becomes weather-dependent, the system needs flexibility on both sides — reducing demand when generation is low, and increasing it when there is surplus that would otherwise be curtailed. Flexible demand is frequently the cheapest source of both.
What limits it:
Most demand is not genuinely flexible, and shifting it causes real inconvenience.
Payback and rebound. Deferred consumption returns later, sometimes creating a secondary peak.
Measurement requires establishing what would have happened otherwise — the counterfactual baseline — which is genuinely difficult and is where disputes arise.
Participation requires enabling technology — smart meters, controllable appliances — and access is uneven.
Vehicle-to-grid extends the idea to discharging back.