Energy-efficient cooking


What do you need to consider when looking at the energy and environmental aspects of cooking? Alan Pears begins the discussion.

In energy and environmental terms, cooking is just one part of a complex system in the food supply chain. The food system accounts for around 25% of greenhouse gas emissions in Australia. Of that, cooking is a small part, about 3%. The other factors such as the production, transport, sourcing and types of ingredients are major issues that we don’t have space to tackle here.

Even though energy use from cooking is a relatively small portion of food-related energy use, it can still be significant. An average Australian home uses around 600 kilowatt-hours (kWh) of electricity each year for all-electric cooking (costing $150 or more), while gas cooking typically uses 3 to 5 gigajoules (GJ), costing $60 to $250 depending on usage and gas price. Many homes use a gas cooktop and electric oven. Most homes also have several benchtop cooking units such as microwave ovens, toasters, electric kettles and rice cookers.

Energy use for cooking is particularly an issue for households that are off-grid. Many off-grid homes use gas for cooking rather than electricity (because of the high loads from electric cooking appliances), yet this still has a greenhouse gas impact, and can be expensive when it’s LPG rather than natural gas.

Electric cooking can also be a major contributor to evening peak electricity demand. As electricity suppliers introduce time-of-use pricing or peak demand charges, it will be important to manage cooking demand. Gas prices are also increasing, while LPG is already very expensive.

So energy-efficient cooking and reduction of peak energy demand for cooking are important. This article looks at these issues.

Where is energy wasted in cooking? 

As with all energy efficiency analysis, standby energy use can be an issue. The way you heat up (or defrost) food can also affect energy use, as does the way you manage cooking post the ‘heating up’ phase. And then, the appliances themselves (such as ovens, grillers etc) all have their own efficiencies and optimal usage patterns.

The energy use of kitchen lighting and non-cooking appliances (fridges and dishwashers) should also be considered, but they have been well covered elsewhere so won’t be discussed here. But, just as an example, lighting a kitchen with six halogen lamps for two hours a day uses half as much electricity as cooking.

Standby energy 

Luckily, gas cookers no longer have pilot lights that cost a lot to run. But many cooking appliances use energy when on standby for clocks, ‘smart’ features, electronics and in some cases keeping components hot, ready for action. Standby consumption is declining, but older equipment and even some new products, such as coffee makers, can have surprisingly high standby consumption.

A good rule of thumb: if you’re not confident an appliance has standby power under 1 watt, switch it off at the power point.

Read the full article in ReNew 130.