A Review of The Energy Intensity of Cooking Appliances and Cooking Practices - Implications for The Cost of Cooking - Archie Lasseter for Utilita 27/04/2022

Abstract

Cooking uses a considerable amount of energy in the home. Reducing this energy consumption is poignant, considering the current cost-of-living and climate crises. A review of literature and online stores to find the energy intensity of a range of cooking appliances is completed. The findings are used to calculate a financial and environmental cost per type of appliance. A further literature review to identify the effect of different cooking practices on energy use is completed. Combined, these studies present a ‘cost-to-cook’. This can be used to select the cheapest appliance to cook with and inform possible reductions in energy use through behavioural change in cooking methods.

Introduction

Reducing energy consumption in the home through changing consumer behaviours is a significant element of achieving net zero by 2050, necessary to achieve the aim of the Paris Agreement¹. This will simultaneously alleviate the recent unprecedented rise in energy prices and climate crises^{1, 2}.

Many factors affect the amount of energy used in the home. These factors can be categorised into socio-economic, dwelling and appliances³. Factors within these categories are interrelated. For example, money spent on energy efficiency measures such as double-glazing increases as household income increases, somewhat offset by an increase in the number of appliances present as household income increases⁴.

The key factors affecting energy consumption from appliances are presence of appliance, frequency of use and energy demand when in use³. Specifically for cooking, the method used has a considerable impact on amount of energy used^{4, 5}. For example, using a lid to simmer can reduce energy consumption between 50% and 85%⁵. Accordingly, behavioural change in cooking practices has the potential to significantly impact energy consumption in the household⁵.

Energy Intensity of Appliances

Appliance categories are defined and energy consumption in watts and size of appliance is collected for 205 appliances across 62 sources. Watts/size-of-appliance is multiplied by average appliance size to control for size and calculate average wattage. Average wattage is divided by 60 to calculate energy use in Whr/minute. This is multiplied by an electricity price of 28.343p/kWh and 7.336p/kWh for gas and divided by 1000 to calculate financial cost in pence/minute-of-use⁶. A carbon cost is calculated by multiplying Whr/minute by 0.21233 kgCO₂e/kWh for electricity and 0.18316 kgCO₂e/kWh for gas⁷. The results are shown in a table 1.

Limitations

Many appliances have different settings to adjust the amount of energy being used. For example, gas marks or temperature settings on ovens. Manufacturer specified rated energy use has been used, which is the maximum energy the appliance would use on full power. This assumes the appliance is 100% efficient at converting input energy into useful cooking energy. Secondly, a varying number of sources are used per appliance type. This is inherent when dependant on availability of existing literature. This means results for some appliances are more robust than others. Real world, standardised tests measuring the amount of energy used during cooking would yield more useful results. This would account for the undeniable energy losses from cooking. Logistically this would be a far more challenging study to conduct. In its absence, this study hopes to be a useful starting point to aid the discussion on cost-of-cooking and provide a useful building block for further research.

Cooking Practices

There are many ways to reduce the energy used during cooking by following good practices. Based on a review of existing literature one paper stood out, Hager & Morawicki, 2013⁵, which reviewed literature on energy consumption during cooking. See table 2 below.

Table 2. Adapted from Hager & Morawicki, 2013.

Cooking Practices	Reduction in energy (%)
Simmering (∼90 °C) rather than boiling (100 °C)8	From 69 to 95%
Steaming rather than boiling9	From to 56%
Turning everything off and using residual heat to finish cooking with10	From 17 to 23%
Put a lid on a pan so you lose less heat, and boil quicker and stays boiling with heating the pot to a lower temperature8	From 50 to 85%
Using a pan with a diameter larger than the heat source to reduce heat loss from around the edges11	From 31 to 40%
Use a non-distorted pan with a flat base12	From 42 to 68%
Once you've heated something up put it in an insulted container e.g., make lots of coffee and put it in a thermos for the day13	From 42 to 68%
Using a larger pot size to increase the surface area you are heating (but don't under fill the pot or pan)11	From 42 to 63%
Filling pot to capacity (empty space means wasted heat)11	From 20 to 49%
Cooking larger quantities at once and store the rest10	From 78 to 83%
Monitoring internal temperature can mean you are heating things to the most appropriate temperature14	From 19 to 50%
Soaking some foods before cooking14,15	From 3 to 19%

References

1. CCC. The Sixth Carbon Budget.; 2020. Accessed April 23, 2022. https://www.theccc.org.uk/wp-content/uploads/2020/12/The-Sixth-Carbon-Budget-The-UKs-path-to-Net-Zero.pdf
2. Ofgem. Wholesale market indicators. https://www.ofgem.gov.uk/energy-data-and-research/data-portal/wholesale-market-indicators.
3. Jones R v, Fuertes A, Lomas KJ. The socio-economic, dwelling and appliance related factors affecting electricity consumption in domestic buildings. Renewable and Sustainable Energy Reviews. 2015;43:901-917. doi:https://doi.org/10.1016/j.rser.2014.11.084
4. Leahy E, Lyons S. Energy use and appliance ownership in Ireland. Energy Policy. 2010;38(8):4265-4279. doi:https://doi.org/10.1016/j.enpol.2010.03.056
5. Hager TJ, Morawicki R. Energy consumption during cooking in the residential sector of developed nations: A review. Food Policy. 2013;40:54-63. doi:https://doi.org/10.1016/j.foodpol.2013.02.003
6. Ofgem. Default tariff cap level: 1 April 2022 to 30 September 2022. https://www.ofgem.gov.uk/sites/default/files/2022-02/Default_tarif_cap_level_v110.xlsx. Published online 2022.
7. BEIS. Conversion factors 2021: condensed set (for advanced users) - revised January 2022. Greenhouse gas reporting: conversion factors 2021. Published online 2022. Accessed April 25, 2022. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1049333/conversion-factors-2021-full-set-advanced-users.xlsm
8. BRUNDRETT GW, POULTNEY G. SAUCEPAN LIDS: THE KEY TO LOW ENERGY COOKING. Journal of Consumer Studies and Home Economics. 1979;3(3):195-204. doi:10.1111/j.1470-6431.1979.tb00561.x
9. Warthesen JJ, Vickers ZM, Whitney-West S, Wolf ID. Cookery Methods for Vegetables: Influence on Sensory Quality, Nutrient Retention, and Energy Consumption. Home Economics Research Journal. 1984;13(1):61-79. doi:10.1177/1077727X8401300109
10. Carlsson Kanyama A, Boström-Carlsson K. Energy Use for Cooking and Other Stages in the Life Cycle of Food A study of wheat, spaghetti, pasta, barley, rice, potatoes, couscous and mashed potatoes. Published online April 2001.
11. S.D. P, M. Newborough. ENERGY-CONSCIOUS DESIGN IMPROVEMENTS FOR ELECTRIC HOBS. Journal of Foodservice Systems. Published online 1987.
12. Probert D, Newborough M. Designs, thermal performances and other factors concerning cooking equipment and associated facilities. Applied Energy. 1985;21(2-3):81-222. doi:10.1016/0306-2619(85)90069-8
13. Oberascher C, Stamminger R, Pakula C. Energy efficiency in daily food preparation. International Journal of Consumer Studies. 2011;35(2):201-211. doi:10.1111/j.1470-6431.2010.00963.x
14. Das T, Subramanian R, Chakkaravarthi A, Singh V, Ali SZ, Bordoloi PK. Energy conservation in domestic rice cooking. Journal of Food Engineering. 2006;75(2):156-166. doi:10.1016/j.jfoodeng.2005.04.005
15. ROY P, SHIMIZU N, KIMURA T. Energy Conservation in Cooking of Milled Raw and Parboiled Rice. Food Science and Technology Research. 2004;10(2):121-126. doi:10.3136/fstr.10.121

Example Data

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Party Food

Breaded and Battered Chicken

Potato Products