This shows fuel poor households as a percentage of all households in the area. A household is said to be fuel poor if it needs to spend more than 10 per cent of its income on fuel to maintain an adequate standard of warmth. This is usually defined as 21 degrees for the main living room and 18 degrees for other occupied rooms. Although the emphasis in the definition is on heating the home, fuel costs in the definition of fuel poverty also include spending on heating water, lights and appliance usage and cooking costs. The fuel poverty ratio is calculated as required fuel costs (i.e. required usage * costs) divided by income. If the ratio is greater than 0.1 then the household is fuel poor.