How Much Power Do We Need?

How much power would it take to assure everyone on Earth had access to decent medical care? Clean water? Adequate nutrition? Air conditioning for the more intense heat waves of the future? How about phones, computers, and all the infrastructure needed to make and support them? What if thousands of kilometers per year of traveling is added in, and the vehicles needed to do this?

There have been a series of studies that have set out to quantify how much power it takes for a “decent living” around the world. In many ways it’s stunning to see how little is needed compared with what is currently used. The poorest billion people on the planet (the approximate number of people without access to electricity) could have access to not just electricity but all of these conveniences for less than 0.5 TW.

What is decent?

A decent living is certainly culturally and individually dependent, but it can be useful to attempt quantifications. Rao and Min defined a set of minimum material requirements for human flourishing, as an alternative to income or development indices as indications of poverty. Millward-Hopkins, Steinberger, Rao, and Oswald have estimated minimum energy needs for these standards, assuming energy-efficient options are used to provide the needs. This chapter summarizes the Millward-Hopkins et al paper, which is highly recommended as further reading, including the extensive supplementary material.

The categories, specific needs, and world averaged minimum power in watts per person are the following:

Category Needs Minimum per capita power required (world average)
Nutrition Adequate calories, nutrients, cold storage, and cooking appliances. 100 W
Shelter Construction with adequate floor space, illumination, climate control 45 W
Hygiene Clean water, water heating, waste management 50 W
Clothing Enough for comfort and washing facilities 20 W
Health care Access to hospitals 50 W
Education Access to schools 10 W
Information technology Smartphone, laptop, networks and data centers 20 W
Mobility With public transportation or private vehicles 100 W
Other Power supply infrastructure, retail and shipping 90 W
Total 485 W

 

 

Their estimates include all sources in these categories, including construction and transport of any goods. For instance, if a refrigerator has an average lifetime of 14 years, then the energy required to make one refrigerator divided by its lifetime of 14 years is used as the average power required to produce a fleet of such devices.

Many energy-intensive options are included, such as some meat for nutrition and an occasional airplane flight. The requirement of higher efficiency, though, means that in categories like temperature control of residences, significantly less energy is used compared with average structures of today. This is accomplished with well-insulated structures and equipment like high-performance heat pumps.

The decent living requirement for energy use in the study is only 485 W per person, a remarkably low value, less than one quarter of the per capita power required to satisfy the North American demand using electricity. Even for a future potential population of 10 billion people, the decent living requirement could be met for everyone with under 5 TW of power. Solar panels with efficiency of 20% placed over just 0.1% of the Earth’s surface could provide this amount of power for over 10 billion people.

Power usage by category

Which of the basic needs described above require the largest amounts of power, and which require the least? We’ll examine this both in the context of understanding the sensitivity to different assumptions about what constitutes a decent living, as well as to imagine which needs could be satisfied with less frugality with little impact on overall power usage.

Power usage is generally spread among sectors. The largest is nutrition, contributing over 100 W. The minimum energy diet has the required calorie intake depending on a person’s age, and assumes half as much meat consumption as in the healthy omnivore’s diet from a recent study of the environmental impact of food choices. This amounts to 12 kg of meat per person per year, half the current global average, and an 85% reduction as compared with the meat-intensive diets of the US or Australia.

Each calorie of vegetarian food is assumed to take 0.2 calories of energy in the form of fertilizer creation/application, fuel for tractors or other farm equipment, and the creation of machinery. Current values around the world are more like 0.25-0.33 calories in per calorie out, so this assumes a small increase in efficiency. For beef, the input energy required is 24 times larger than for vegetarian food, for poultry and eggs it is 11 times larger, and for dairy it is six times larger. In total, to grow enough calories for this hypothetical low-impact diet requires a little less than 30 W/person. Although only 7% of the calories in this diet are sourced from animals, they account for 44% of the energy usage.

In wealthy countries, the energy that goes into processing, distributing and cooking food is much larger than that used to grow food, by a factor of 3-4. Distribution, including packaging and refrigeration within grocery stores, adds 43 W/person. In the minimum energy scenario, food is assumed to be produced more locally and with less processing than in high-consuming countries of today. The energy required for transporting food is 3 W/person (about half as much as estimates for today), and for processing is 14 W/person (around 40% of estimates for today).

A large amount of food is wasted worldwide, perhaps up to 50%, according to some calculations. Assuming this is minimized significantly to a mostly unavoidable value of 15% waste adds another 13 W/person.

Efficient cooking appliances used on half the food that is cooked requires another 10 W/person, with less than 1 W/person going to the energy embodied in the appliance. Refrigeration adds 6 W/person, assuming top efficiencies of today’s best appliances, which use 80% less power than the world average. About 40% of that is in the creation of the refrigerator. All in all, this adds to about 116 W/person for an adult, or 109 W/person when children and their lower nutritional needs are taken into account.

Source Power required per adult Notes
Growing vegetarian food 16 W 93% of calories
Growing animal-based food 12 W 7% of calories
Distribution 42 W
Transport 3 W Half of today’s usage
Processing 14 W 40% of today’s usage
Waste 13 W 15% of food wasted, compared with as much as 50% today
Cooking 10 W
Refrigeration 6 W
Total 116 W

Housing is assumed to be within residences of 4 people on average, with 20 m2 of common space and 10 m2 of individual space, for a total of 60 m2 (646 square feet) per dwelling. Average homes in the US are around 1600 square feet, and new constructions average 2000 square feet, over three times the decent living value. Further, US dwellings now average only a little over 2.5 persons/household, as compared to the 4 person/household assumed here. Dwellings around the world are increasing in size, and vary substantially from country to country. Square footage of housing matters for house construction energy costs, as well as the illumination and heating/cooling needs.

Power required for heating and cooling varies significantly with location. The minimum values assume well-insulated residences heated and cooled with high-performance heat pumps, either within new constructions or high-quality retrofits. The average power across climate zones is then between 10-20 kWh/m2, or 1-2.3 W/m2. Temperature control thus requires around 15-35 W, with the highest values in Canada, Kazakhstan and Scandinavia, and the lowest values in South Africa and Portugal. Some current constructions use as much as ten times as much energy for climate control per square foot.

Illuminating this small amount of floor space with a highest efficiency light-emitting diode (LED) bulbs requires only 1 W in the DLE calculation. This assumes one-third of the floor space (i.e., 5 m2) needs a 4 W, 625 lumen bulb that is on for 6 hours per day.

Construction of residences depends a lot on the materials used, with steel embodying much more energy than timber or concrete. Assuming long lifetimes of buildings (around 80 years) and best efficiency practices, residential construction ends up averaging 15-24 W/person.

It’s important to recognize that the amount of energy to create residences is usually much larger than these estimates, routinely 10 to 100 times as much. A mansion (defined by 8,000 square feet of floor space) with five residents living in it works out to ten times as much floor space as the decent living standard on a per capita basis. The embodied energy usage for such a structure, even under best efficiency practices, would thus work out to 150-240 W per person averaged over the building’s lifetime. More normal efficiencies, shorter expected building lifetimes, or the use of steel would require two to ten times the energy for construction. Construction of a large residence can eat up a lifetime’s worth of the decent living energy standard, for the whole family. The substantial recent increases in second home purchases in the United States is further evidence of the role of affluence in causing all varieties of ecological crises.

Hygiene includes water supply, heating and waste management. It is estimated that people need at least 50 liters (13 gallons) of water per day, including 5 L for drinking, 20 L for sanitation, 15 L for bathing, and 10 L for cooking. The average American uses around 310 L (82 gallons) per day.

In dry regions, extraction or long-distance transport of water can be rather energy intensive, especially if desalination of water is required. But generally speaking, the energy that goes into water treatment and infrastructure (3-10 W/person) is much less than home water heating usage. Reasonable minimum values for hot water assume the daily use of 15 L of hot water for bathing (equivalent to one short, hot shower per day) and 5 L of hot water for sanitation. Since the amount of heating required depends on the initial temperature, hot water energy costs are larger in cold climates (50 W/person in Canada) and less in mild climates (22 W/person in Burkina Faso).

Waste management, assuming less consumption and waste under the minimal use scenario, is assumed to be only 6 W/person across countries.

Clothing requires energy in its production and in washing. Given typical lifetimes of clothes, the new clothing purchasing requirements are three tops per year, three sets of underwear, and one per year each of bottoms, sweaters, jackets and shoes. Assuming lower than average energy intensity for cotton, wool and rubber, the power required to make this amount of clothing per year amounts to 12 W/person. Without the assumed efficiency gains, this amount of new clothes would require about three times more power.

Washing of clothes adds around 9 W/person, with about three-fourths direct use and the rest from the production of washing machines. The usage figures assume much less energy for washing clothes than most people use, and the main savings comes from the simple flick of a switch, from hot to cold wash. Since 85% of power for washing clothes goes to heating water, this simple change is an easy way to save energy around the home. With modern detergents, cold water washing is just as effective for nearly all needed cleaning.

Health care and education require adequate space and energy. Assuming 10 m2 of school space per student, and double the power requirement for heating and cooling in an educational space yields about 30-40 W/student, or 3-10 W/person depending on the percentage of the population between ages 5-19 (10-30% depending on the country). Schools are assumed to require 3 times the construction energy of residences, which is a similar value to office buildings. This works out to 4-12 W/person on the country average.

Hospital space needs assumes 200 m2 per bed of hospital space, 8 beds per 1000 people, and double the energy needs as for heating and cooling. Then this is multiplied by 3 for the entire health care sector energy usage, assuming hospitals constitute only one third of the total energy. This adds up to 20-28 W/person. Health care building construction is assumed to require 9 times the energy of residences, due to their reliance on special equipment. Thus 14-23 W/person are required for health care building construction.

Information technology needs assume that everyone over 10 years old has a phone and each household has a laptop. Smartphones typically use a maximum of 5 W, and 1 W in standby. Assuming each device is completely powered off for a portion of the day as well, the study assumes an average usage of a little less than 1 W.

Smartphones have short average lifetimes, due in part to their “planned obsolescence” and the fact that owners typically don’t have the right to repair them. These are corporate tactics designed to increase company revenue, at great expense to the public and to the environment. Companies often make products for government use that are designed to last longer, but do not make them available to the general public. Legislation to allow the public to purchase more durable equipment, or the enactment of right-to-repair laws could help to extend lifetimes of high energy and material footprint products.

Phones typically require more energy to produce than they consume over their usage, but this is not inevitable. The Fairphone is a device sold in Europe that is designed to be easily repairable, in order to extend its lifetime to 5 years. Assuming industry-best efficiency practices to make such a phone, the energy to produce the phone over its 5 year lifetime in this scenario is about 0.6 W. Thus the total cell phone usage is around 1.5 W.

Laptops also require a lot of energy to produce, and suffer from the same planned obsolescence as mentioned above. Processor energy usage, especially of graphical processing units (GPUs) as used in gaming systems, is soaring. Current generation game consoles can exceed 200 W when running power-intensive games, not counting the power consumption of the television. Gaming totals around 2.4% of electricity usage in the US, equivalent to several gigawatts.

If laptop lifetimes were able to be extended to 10 years, and the tendency towards increasing energy usage were curtailed, one could imagine a laptop using only around 7 W of power on average, with slightly larger power used to construct the device. If these 16 W are divided among 4 people, then the power usage can be only 4 W/person.

Data centers, Wi-Fi and cellular networks use a tremendous amount of energy, forecast to be around 1 TW by 2030 and potentially as high as 3 TW. Even in the decent energy standard calculation, data centers and network infrastructure end up using more than the production and use of laptops and phones combined. Each phone requires 5 W for networks and data centers, while each laptop requires 28 W.

Information technology Power usage per phone Power usage per laptop
Direct usage 1 W 7 W
Manufacturing 0.6 W (over 5 year lifetime) 10 W (over 10 year lifetime)
Network/data usage 5 W 28 W
Total per device 6 W 45 W

Power required for information technology under DLE scenario. 

For mobility, the world average transportation is around 7,000 km/person/year (4350 miles/person/year). The US stands out greatly over the rest of the world, at around 3 times the world average. The minimum energy process assumes 7,000 km/person/year in urban areas and 10,000 km/person/year in rural areas as a first step. Then, these values are scaled upward and downward based on the lived population density of each country, resulting in mobility averages ranging from 4,900-15,000 km/person/year.

Movement is assumed to be 1,000 km/person/year of non-motorized transport (walking and biking), 1,000 km/person/year of air travel, and the rest of the required mobility (2,900-13,000 km/person/year) handled by trains (40% of remainder), buses (40% of remainder), and extremely lightweight and efficient cars with carpooling (20% of remainder). Assuming increases in efficiency leads to 40-70% reduction of current energy usage and including the energy to produce each gives the table of energy usage per 1000 km/year shown below. When combined with the average mobility requirements for each country, the final power requirements are 65-120 W in urban areas, and 85-170 W in rural areas.

Mode of transportation Direct power usage (per 1000 km/year) Indirect power usage (per 1000 km/year)
Airplane 30 W 7 W
Train 2 W 7 W
Buses 6 W 3 W
Carpool (3 people/vehicle) 11 W 7 W
It’s worth noting that not all of this power usage would show up on one’s electricity bill. Many of the categories involve power usage off-site, like the power required to grow crops or manufacture appliances. The total usage within the home totals to approximately 66-136 W depending on location. On an energy bill, this is equivalent to 48-98 kWh/month, or 578-1191 kWh/year. This includes power for cooking (9 W), refrigeration (4 W), clothes washing (5 W), phone (1 W), laptop (2 W), and illumination (1 W), independent of location. Heating and cooling amount to 15-35 W, depending on location, and hot water heating totals between 22-50 W. The average car usage amounts to between 7-29 W, depending on location and whether the residents are urban or rural.

Connect

Meet Prof. Julia Steinberger, the lead investigator of the Living Well Within Limits project that led to the Decent Living with Minimum Energy study described in this chapter.

 

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