BNW06: Assumptions underlaying the energy projections for tumble dryers
This brief and referenced information is a public consultation document and will be used to inform Government decisions. The information and analysis in the brief forms part of an integrated, public domain knowledge base that is managed and held by Defra’s Market Transformation Programme. The policy scenarios and action plans are illustrative, intended to stimulate discussion and do not imply commitment by Government nor by any other body.
1 Background
This notes sets out the information, rationales and assumptions make in the Market Transformation Programme Policy Brief for electric tumble dryers.
2 Reference Scenario
The Reference is the baseline scenario that describes underlying trends and technology developments.
2.1 Current market policies and activities
European Energy Label – October 1996
Introducing the A to G energy efficiency classes for both electric vented and condenser tumble dryers.
There is a guidance note on the implementation of energy information regulations.
Energy Saving Recommended
Energy Saving Trust scheme to highlight products that demonstrate best practice in terms of energy efficiency, thus allowing consumers to more easily identify products. The scheme is open to all manufacturers. Products meeting set criteria are able to display the ESR logo at point of sale and in promotional material.
The scheme aims to review the criteria as the efficiency of appliances improves to maintain a ‘best practice’ recognition for recommended appliances.
Criteria for tumble dryers (2002):
- A and B rated energy efficiency class
Because very few products were available that met these criteria or were put forward for the scheme, from February 2006 the criteria were revised to extend the scheme to include tumble dryers that were energy efficiency class C rated and used sensors to dry loads to a predetermined level. Using sensors is believed to prevent users from overdrying their loads and many such dryers also offer the option of different levels of dryness to allow loads to be ironed.
2.2 Reference case modelling
The projections are based on several interdependent considerations:
Household numbers
The number of households is assumed to rise from 24,739,000 in 1999 to 28,467,000 in 2020 1
Percentage ownership
Tumble dryer ownership was assumed to be at 34.6% in 1999 (DECADE Run 5). Market data from 2001 puts the percentage ownership at 40%2, a level maintained for subsequent years.
[Office of National Statistics figures for 2002-2003 suggested ownership of tumble dryers to be 56%, however this figure includes washer dryers]
The split between vented and condenser dryers was assumed to be about an 80/20% split (for stock prior to 1999). By 2002, sales (Gfk data) levels show a split of 60% vented to 40% condenser dryers.
Compact and full size tumble dryers are included in the modelling. For vented dryers a proportion of D rated and all of the F and G class dryers are compact.
Sales and stock replacement level
Using actual sales data (Gfk) from 2002 3 it is possible to calculate the replacement period in relation to the stock number (calculated from household numbers and percentage ownership).
From this the following lifetime is assumed.
|
|
Vented dryers
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Condenser dryers
|
|
Lifetime (years)
|
8.2
|
11.2
|
For projecting forward the number of sales to maintain the stock, assuming the above replacement rate, is calculated for subsequent years.
The percentage of sales according to the different energy efficiency class is projected forward from 2002 (where actual sales are known). There is a minimal move to increased sales of more efficient tumble dryers, as there doesn’t appear to be any introduction of improved technology to facilitate this.
For vented dryers sales it is suggested that sales plateau a level with 70% sales of C rated appliances and most of the rest being D rated.
Efficiency of models available and sold
Energy use calculations are based on tumble dryers being used 148 times a year 4. (This is 60% of the number of times that a washing machine is used – for household owning a tumble dryer).
Historic data has assumed the average annual unit energy consumption is 373 kWh (for stock in 1999).
Using this as a basis it is possible to determine the typical consumption for each programme and extrapolate consumption for the different energy label classes (as shown below). These kWh consumptions per cycle are less than the data given on the energy label for a typical sized dryer (using maximum capacity), because consumers dry less than the maximum capacity.
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kWh per cycle
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A
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B
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C
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D
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E
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F
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G
|
|
Vented dryers
|
1.71
|
1.98
|
2.24
|
2.51
|
2.78
|
3.05
|
3.35
|
|
Condenser dryer
|
1.84
|
2.14
|
2.45
|
2.75
|
3.05
|
3.35
|
3.69
|
These calculations provide the annual unit energy consumption for the base year of 1999 and subsequent years in the modelling (therefore any changes in the average load capacity of the appliances, which would affect average consumption is not taken into account).
Gas Tumble dryers
The MTP assumes that the ownership of gas tumble dryers will remain a minority. In the late 1990s it was considered to be only 0.3% of households and this percentage is only likely to increase very slight to 0.4% in 2010 (due to the general increase in household numbers).
Gas dryers are more carbon efficient because they use the primary energy source. However, barriers to increased ownership are assumed to be initial purchase price and limited flexibility in installation (most houses with gas would require an additional gas connection point).
Gas tumble dryers are not separately identified in the MTP projections (in the MTP What If tool).
3 Assumptions for Earliest Best Practice Scenario (EBP)
The projection is constructed from the Reference scenario and assumes that all consumers are purchasing the best available appliance from 2004; C rated for full size and D rated for compact (vented).
Better could be achieved with tumble dryers using heat pump technology but this type of appliance is not seen as economically acceptable to consumers at the moment, so not available in the UK. (This type of appliance could use 2.6kWh5 per cycle [A rated EL tested with max load]).
(The only A rated model in the UK is based on a drying cycle taking around 8 hours and it is assumed that few consumers would use this programme, and that the energy consumption for other programmes used is the same as other typical vented dryers)
Changes in consumer behaviour (eg different loading or programme times) is not incorporated into the projection.
4 Assumption for Policy scenario (P1)
The P1 scenario is based on the Reference scenario and incorporates proposed policy or other possible market influences (eg. industry voluntary agreements). Changes in consumer habits are not included in the modelling.
The following activities have been incorporated into the P1 scenario.
Energy Saving Recommended
The revised criteria for washing machines (from July 2004) includes higher spin efficiency. Better spin efficiency and therefore water extraction from the washing load should reduce drying times and energy required by tumble dryers. A 10% saving in energy consumption per drying cycle has been assumed6.
However, adjustments for this hasn’t yet been included because further information about the habits of tumble dryers users is needed to measure the true effect.
Minimum Standard
A maximum consumption regulation, or voluntary agreement, that would limit the efficiency of models to C or better. This would lead to a shift in the sales to more efficient models (in 2002 around 20% of sales where below C rated).
Although there appears to be little focus on this opportunity the P1 scenario assumes an agreement being finalised by around 2006 with the influence beginning to be seen in the market from around 2008.
Energy Plus
There was in the past consideration of using the Energy + scheme (successful for cold appliances) could help to bring more efficient tumble driers into the market place. It is still an option, but not considered to be very likely.
5 Issues
User habits
Ownership of tumble dryers has changed relative to earlier MTPs projections, it is also possible that the way they are used has also changed. There is also little known about the habits of compact (3kg) tumble dryer users.
In order to consider options such as promoting sensor dryers, further information about user habits is necessary to determine if non-sensor dryers use more energy because users set them to maximum timing and therefore dry for longer than necessary.
Is more up to date or detailed user habits information available?
Electric vs Gas
The policy package for tumble dryers is based around promoting more efficient electric tumble dryer technology. Promoting gas tumble dryers may be more effective in terms of carbon savings. (Energy Efficiency schemes have been run in Northern Ireland)
What is the calculated benefits of using gas dryers and what are the barriers to wider tumble dryer take up? How can barriers be overcome?
With feedback, questions or comments, please contact:
or call the MTP enquiry line on +44(0)845 600 8951, quoting the document reference