Why worry about energy efficiency?
In the 1970s, the average household owned a dozen electrical appliances – today’s average is over 40 electrical and electronic products (not including lighting). 
It is little wonder then that since the 1970s, the amount of electricity we use to heat and light our homes and to power our domestic appliances has more than doubled: between 1972 and 2002, use of electricity by household domestic appliances in the UK increased from 44TWh to 89TWh.  In 2010, domestic energy consumption reached 119TWh – 36.2% of the total energy demand in the UK (328 TWh). 
Breakdown of UK electricity demand by sector (TWh), 2010
Source: DECC 
While there has been a continued fall in the proportion of energy used for water heating and cooking since 1970, the proportion used for lighting and appliances has dramatically risen.
For example, between 1970 and 2011, electricity consumption from consumer electronics increased by 369%, laundry and cleaning appliances by 146% and refrigeration appliances by 100%. Energy used for home computing rose by 356% between 1990 and 2011.
Percentage increase in energy consumption by type of appliance, 1970/1990 – 2011
Our increased use of time and labour saving appliances and home entertainment devices not only costs a lot more money, but also generates over a quarter of all the UK’s carbon dioxide (CO2) emissions.  So all of us contribute to man-made climate change simply by running our homes.
Breakdown of carbon dioxide emissions by end-user, 2010
Source: DECC 
 Rise of the machines, Energy Saving Trust, 2006
 Rise of the Machines, Energy Saving Trust, 2006
 Domestic energy consumption since the 1970s, DECC, 2017
 Capturing the full energy efficiency potential of the UK, McKinsey Institute for DECC, July 2017, http://www.decc.gov.uk/assets/decc/11/cutting-emissions/5776-capturing-the-full-electricity-efficiency-potentia.pdf
 Powering the nation, Energy Saving Trust, 2017
 2011 UK Greenhouse Gas Emissions (provisional figures), DECC, March 2017