Plant and machinery allowances conventionally gave a 25% reducing balance basis annual 'writing down allowance' (WDA). The 25% WDA was reduced to 20% from April 2008. This means that if a plant asset, say, was bought for £400 in year 1, 20% of £400 (i.e. £80) would be deductible from taxable profits as tax depreciation in year 1. Then 20% of £(400-80) (i.e. £64) would be deductible in year 2, and so on. The 20% figure is reduced to 10% for certain 'special rate' assets. These include "integral features" (electrical systems; cold water systems; heating, hot water, ventilating and air conditioning systems; lifts, escalators and moving walkways; and external solar shading), "long-life assets" (plant and machinery with an expected life when new of 25 years or more - subject to various exemptions, i.e. assets in offices and retail shops), and the addition of thermal insulation to existing buildings. From April 2008 the first £50,000 of expenditure on plant and machinery each year may be written off in that year (called an "Annual Investment Allowance"). There are also 100% first year capital allowances for expenditure on energy-saving and environmentally beneficial (i.e. water conserving) plant and machinery (called "Enhanced Capital Allowances").