Generally, anything that uses power is an electric load, with its usage measured in watts. As loads are a measure of power, they determine how much electricity is required to operate an appliance or asset.
Different types of electrical loads
When looking at the definition of load in electricity, we can look at loads in a household or loads in a power system:
Domestic load
A domestic load is the energy that is consumed by domestic or household appliances, such as televisions, toasters, kettles, hair dryers, washing machines, fridges, and the list goes on. As every household has different appliances installed or plugged, the domestic load varies from household to household. To understand the difference between the three, it is important to understand that voltage (measured in volts) is the amount of potential energy between two points on a circuit, while current (measured in amps) is the rate at which the charge flows past a point in the circuit.
Within a household, there are three main types of electrical loads:
- Resistive loads: any electrical load that consists of a heating element, such as lamps, ovens, toasters or space heaters. Current and voltage patterns are in sync.
- Inductive loads: uses wire coils to store magnetic energy and create an inductive field so that the current wave lags behind the voltage wave. Examples here are dishwashers, washing machines, refrigerators or air conditioners.
- Capacitive loads: provide the largest power factors and are often used to boost electrical circuits – they are only used to support other electrical loads, such as inductive loads. Here, the current peaks before the voltage does.
Power system loads
Gross load
Gross load refers to the total amount of energy that is required to serve demand for a country or region throughout the day. Gross load peak is the electricity required at its highest level of the day, usually occurring in the late afternoon when consumers’ demand for energy increases.
Residual load/ net load
Residual load, also referred to as ‘net load’, is the gross load minus electricity generated by variable renewable energy (VRE), such as solar or wind. It essentially shows how much demand is left for conventional power plants to operate.
Gross load and net load in Europe in July 2023
As the capacity of VRE increases, the net load drops, and can even fall below zero. Therefore, it can be further divided into positive and negative residual load:
Positive residual load describes the situation in which renewable energy resources such as wind or solar do not produce enough energy to meet demand. The residual load is thus positive.
Negative residual load occurs when variable renewable energy not only covers all electricity demand but also provides a surplus of energy. As renewable energy capacity is still growing, negative residual load is currently still rare. It is most common in countries with a high solar power capacity, such as Germany and Spain and usually occurs in the middle of the day when solar energy peaks, as seen below on three occasions in July 2023.
Positive and negative residual load in Germany in July 2023
Electrical loads in comparison
Different appliances consume vastly different amounts of electrical power. Below is a list of common household appliances and their maximum electrical load.
Electrification and rising electrical loads
As we can see above, heat pumps and electric vehicles – two of the most common electricity-consuming distributed energy resources (DERs) – require a large amount of electrical energy to function. They are, however, flexible assets, which means their electricity flows can be monitored and their usage controlled. When integrated into an energy management system, heat pumps, which provide both heating and cooling, and EVs can be used at optimal times (aka. their consumption is shifted) to minimize costs and they can even be used to store energy thanks to bidirectional charging and thermal energy storage. This not only ‘relieves’ the grid during peak electricity demand periods but it also allows them to store surplus energy and feed it back into the grid when energy supply is low.
Integrating electricity, heating and mobility in this manner is part of a wider trend called sector coupling, which enhances the efficiency and sustainability of energy systems by creating synergies. Adding an increasing number of loads into energy systems, at the same time as increasing variable renewable energy sources can be overwhelming and hard to balance. With holistic smart energy solutions, however, flexible loafs can enhance grid stability and present valuable opportunities.
Load management strategies
Electricity supply and demand loads are often misaligned – for example, consumers often use the most energy in the early evening when the sun is no longer shining. But with the right load management strategy, consumers can adapt to these fluctuations and utilize the full potential of their power-generating and -consuming assets to minimize their electricity bill. Load management refers to the active control of electricity consumption. There are a variety of approaches to manage loads, such as:
- Peak shaving or load shedding in which businesses reduce their electricity expenses by minimizing peak electricity demands and thus, lowering demand charges.
- Dynamic load management, an approach for sites with numerous charge points that considers the load at the grid connection point in real time and adjusts the power supplied to each charge point accordingly to ensure limits are never breached.
- Dynamic tariffs pass on fluctuations in wholesale electricity prices to end users so that they are incentivized to consume electricity (e.g. charge their EV) when prices are low, which typically coincides with high supply.
- Demand-side flexibility is an overarching term for measures that reduce electrical loads during peak demand, usually through load shifting, financial incentives or energy storage.
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