Energy-efficient cooking

Last updated Monday 21 July 2008

Feed yourself without cooking the climate

Changing how we cook only shaves a little off our energy use, but the tips can be fun and addictive, and if you're one of those people who spend half their life in the kitchen, the savings start to add up.

Too many cooks can spoil the climate, scientists say. Although cooking only accounts for about 3% of your home energy use, it adds up. In fact, all of our electric hobs, ovens, kettles and microwaves use as much electricity in a year as British street lighting does in six years.

So there's no harm in finding more efficient ways to prepare our meals. For example, blitzing your frozen veggies in the microwave instead of waiting for them to boil on the hob not only saves time - it also cuts the energy used by a tasty 65% according to the Market Transformation Programme.

And although cooking for one is an inefficient way of cooking (a third of UK households have a single occupant), single cookers can still pick up some tips on saving CO2 and cash.

Read more below
Photo: Energy-efficient cooking

Saves up to 50 kg of CO2 a year

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How do I do it?

Pub Fact

  • Electricity is about four times more expensive than gas - and emits twice as much CO2 per unit
  • The average Brit spends about 75 a year on cooking bills
  • Cooking uses about 830 kWh in the average home in the UK annually
  • Average vitamin C intake is 50% higher than recommended in the UK - in fact a single packet of crisps provides about a quarter of the recommended intake
  • Electric ovens cost the UK about 400m every year - enough to pay the salaries of around 20,000 nurses or teachers
  • Trends suggests we're moving towards ready-meals, microwave ovens, eating out, and takeaway meals and away from the traditional hob or oven

Think about where you cook your food:

  • If possible, switch from an electric to a gas oven. Although gas ovens typically use a tiny bit more energy, the lower CO2 output per unit of gas far outweighs this difference
  • Use a microwave instead of the oven as much as possible - not just for reheating and defrosting, but for fresh food too
  • Use a pressure cooker, which saves large amounts of heat
  • Make toast in a toaster, not under the grill

Think about how you cook it:

  • Use just enough water to cover vegetables and put a lid on the pan - your sprouts will cook more quickly
  • Simmer instead of boiling: less steam means less need to ventilate the room
  • Cut food into smaller pieces to speed up cooking

Think about what you cook:

  • Make one-pot meals - stir-fries and stews save energy on cooking and washing-up
  • Eat poultry rather than beef or lamb (read our meat article)
  • Print out a seasonal food calendar - locally sourced foods mean fewer embodied emissions

Get the most efficient use out of your equipment:

  • Always use the right size of pan for your cooking ring
  • Use pans that can divide into sections so you can cook several items at once
  • Take any shelves you don't use out of the oven, and don't keep opening the oven door while you're cooking
  • Use a kettle to boil water for cooking instead of boiling water on the hob
  • Only fill kettles with as much water as you need. (But make sure you cover the element if you use an electric kettle)
  • Turn the oven off ten minutes before you serve the meal - it will retain plenty of heat for that time
  • Turn off your cooker hood fan after ten minutes especially in winter because it empties your house of heat

Go for economies of scale:

  • Cook for the whole house at once - a full oven is more efficient. You might need to get a lodger first
  • Cook plenty at once and freeze what you don't need that day
  • If you're saving food in the fridge or freezer, let it cool down to room temperature first to save energy cooling it

You can also compost your waste food (both cooked and uncooked, if you have a Bokashi system) and if you're feeling more adventurous, run your car on waste cooking oil.

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How will it make a difference?

  • All of our ovens, microwaves, kettles and other kitchen cooking appliances use up enough electricity in a year to run the UK's street lighting for six years
  • If the UK put all of its cooking on hold (of course, this is unlikely) for a year, national emissions would drop by 1% according to the Market Transformation Programme
  • Switching from an electric oven to a gas oven can save you 15 a year - and cut your emissions as effectively as turning all your appliances off standby
  • Cooking with a gas pressure cooker can reduce the amount of gas needed to cook food by 50% because it allows food to be cooked at a higher temperature, more quickly. You can also now buy pressure-cookers which can sit on top of any hob - gas or electric
  • Microwave ovens use on average half as much energy as electric ovens - but the real saving depends on the type of food. For example, microwaving a frozen ready-meal rather than cooking it in the oven can halve your energy use
  • Under some circumstances, roasting food in the oven can also be much more energy-inefficient than boiling it. In fact, boiling up potatoes in a pot can use ten times less energy than roasting them in the oven

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What's the debate

"I love my chickpeas. But should I buy dried or tinned?"

You'd think that a nasty great tin of pre-cooked chickpeas does more damage to the climate than a humble bag of dried ones. But because cooking small portions of any food at home is far less efficient than cooking it in industrial vats, it actually appears to be better overall to buy pre-cooked pulses. Read more about it in this Guardian article.

"Are modern microwaves really energy savers?"

Traditional microwaves use much less energy than ovens, but newer microwave models waste more and more energy left on standby to power clocks and digital displays. But you can, of course, turn them off at the wall. See our article on avoiding leaving appliances on standby.

"Could a ready-meal be more energy-efficient than home cooking?"

Hard to imagine one of those pre-packaged ready-meals could be a better bet than cooking from scratch with fresh ingredients, isn't it? But a recent Swedish study suggests we're far less likely to chuck out pre-prepared food, so it accounts for fewer methane emissions from landfill. The jury's still out on this one - but see "How do I do it?" for more cooking tips. It's also worth remembering that many scientists believe it's not how the food is cooked but what it is that matters most. (Read our articles on eating less meat and more local, seasonal food).

"Are induction hobs the way forward?"

Billed as super-efficient, induction hobs use only half the power of a gas hob - but because they run on electricity (a fuel which emits slightly over twice as much CO2 per kWh as natural gas), they still damage the climate more than gas hobs. (Switching to a green electricity tariff could help - but not as much as you might think).

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What's stopping me?

"I have an electric oven and I can't afford to replace it."

Surprisingly, just 37% of UK households have gas ovens. But switching to gas has its perks: because electric cooking is three times more expensive than gas cooking, a household could save 50 a year, meaning payback on a simple new model in about four years.

"We don't have gas here."

There are still many homes not connected to mains gas. In those circumstances, liquid petroleum gas (LPG) is an option - but there are installation costs to consider.

"So microwaves are better for the climate than ovens. But what about my health?"

Claims abound that microwaves destroy the health benefits of fresh food (see New Scientist's Microwaves Zap Nutrients, for example) - but they should be taken with a pinch of salt. Microwaves can be the least-damaging way to cook your veggies because they minimise cooking time and temperature. Drowning veggies in water while you cook them is one of the worst things you can do: watery broccoli blitzed in a microwave loses from 74-97% of its antioxidants, according to one study. Raw veg is no answer, however: cooking can release nutrients that your body would otherwise be unable to absorb.

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Comments

ght, Edinburgh 2009-11-18

We had a kitchen re-shuffle and, without thinking about it very carefully, ended up without a freezer. (it's a long story.) A year later, we really haven't missed it. Freezers are lousy for the environment, right? Anyway, it's at least one appliance less to use electricity. The only things we've really missed being able to store in the freezer are 1. ice cream (just means we have to eat a whole litre at a time!), 2. ice cubes and 3. peas (wish the shops would sell them in smaller quantities).

Anonymous 2009-02-22

Buy a remoska it does everthing an oven does but uses a fraction of the fuel

teemay, sudbury suffolk 2009-02-20

One pot cooking is the good, in a pressure cooker is better, you get more nutrients in the final meal.
how about portions of meat or fish in a covered shallow pan with veg brought rapidly to the boil in a centimetre or so of water. The whole can be done in 10 mins max! How much electricity would that use on say two electric hobs if you turn them off at boiling point?

Baz, Shrewsbury 2009-02-08

I disagree with Bloom's comments about ovens. A gas oven must have a combustion air intake and a way for the products of combustion to escape. As with all gas fired appliances, some of the heat goes is lost with the products of combustion up the flue. This must cause a serious reduction in efficiency. By contrast, our electric oven only has a small flue and requires no combustion air to be circulated. Convection currents through this small flue are minimised, mainly to the release of steam. I think it's greener than gas.

Alison, Scotland 2009-01-28

I use a pressure cooker which cuts the cooking time, using less energy. I also use a steamer, either two or three tier depending on what and how much I am cooking.

Freda, Lincs 2009-01-15

I use a two tier steamer, so am only using one ring on the hob instead of three, this is what my gran used to use, also like Spencer I cook veg mixes.

Roger, Gloucester 2009-01-07

I have found that when cooking vegetables they can all be done in the same saucepan by steaming. Using a steamer insert and about 10mm of water with a lid, start with potatoes and carrots for 10minutes then add cauliflower and broccoli parsnips or sweet potatoes for 10 more minutes. Once the water is boiling turn down the heat on the smallest burner to minimum. The flavour is better as well as saving energy.

Anna, Chapel-en-le-Frith 2009-01-07

If you warm your plates up in the oven, try putting a drop of water on each plate and microwave a stack of plates for a minute, really hot plates a lot quicker and more energy efficient than heating them in the oven

poppy, norwich 2008-09-11

cook in the microwave in bulk and then freeze in portions if only cooking for one.

Spencer, Rainham, Gtr London 2008-08-31

If one can control the heat to a simmer, there's no need to cover the vegetables...about 1cm of water can be sufficient: the steam from this water does the rest.

I learned cooking all veg. in one pot when travelling and camping around Australia. I've never done anything else since — and haven't peeled a Potato in thirty years.

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Glossary terms used on this page
CO2
CO2, or carbon dioxide, is made up of the elements carbon and oxygen. It exists quite naturally in our atmosphere, as part of the carbon cycle. Everyday processes in the plant and animal world both add CO2 to the atmosphere and take it out. However, because it is a greenhouse gas - meaning it affects the temperature of the earth - the exact level of CO2 is important. Burning fossil fuels releases CO2 into the atmosphere, hence the anxiety that extensive use of these fuels is causing climate change.
Climate change
Climate change is the variation in the average global or regional climate as measured by yardsticks such as average temperature and rainfall. This variation is caused by both natural processes and human activity. Weather is what happens over days or even hours, whereas climate is the average weather measured over a longer period. Increasingly when people refer to climate change, however, they specifically mean the phenomenon of global warming.
Embodied energy
Embodied energy - sometimes referred to as 'embedded energy' - is the energy used (and therefore the CO2 emissions) in manufacturing, packaging and transporting a product, material or service. So when calculating the CO2 savings from a new energy-efficient product such as a boiler or washing machine, its embodied energy needs to be taken into account. Usually the energy saved in use will quickly compensate for the embodied energy, but in some cases - such as small urban wind turbines - it may be that a product will use more energy in its manufacture than it will save across its lifetime.
Energy efficient
definition to follow
Kilowatt-hours (kWh)
A kilowatt-hour is an amount of energy equivalent to a power of one kilowatt (a thousand watts) running for one hour. The unit is commonly used on electricity meters. If you know how many kilowatt-hours of energy your household uses, you can translate this into kilograms of CO2 emitted by multiplying it by 0.527. A megawatt hour (MWh) is an amount of energy equivalent to the power of one megawatt (a million watts) running for one hour. Similarly, a gigawatt hour (GWh) is a billion watts for one hour, and a terawatt hour (TWh) is a trillion. While your domestic gas bill will be set out in kWh, the output for a power station, for example, will obviously be expressed in one of these much larger units.
Landfill
Landfill is disposal of rubbish by burying it under the ground.
Liquid petroleum gas (LPG)
Liquid (or 'liquefied') petroleum gas (LPG) is a mixture of butane, propane and other light hydrocarbons produced either as a by-product of oil refining or from natural gas fields, and used as a vehicle fuel with lower CO2emissions than petrol. At standard temperature and pressure, it's a gas but the mixture can be cooled, or subjected to moderate pressure, and is then transformed into a liquid for ease of storage and transportation. LPG is used in dual-fuel vehicles, where it operates alongside a conventional petrol tank. It is also used in heating appliances.

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