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Heat pumps - Economics |
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Economics Heat pumps are cost effective for existing buildings if
As the outlet temperature is lower than that with fossil fuelled boilers, it is always cost effective to increase the insulation level and size the heat pump system for the reduced heat loss. The benefit is that the existing radiator system can then be used with a lower heat distribution temperature and so reduce the standing losses in the pipes whilst allowing the heat pump to operate efficiently. For new dwellings which are characterised by a high level of insulation and a low heat loss, heat pumps should always be considered particularly if the distribution system is that of under floor heating or heating/cooling. Adequately sized radiators can also be used though the overall efficiency will be reduced because of the higher water temperature. Initial costs The heat pump is always sized according to the heat loss of the dwelling in order to minimise capital cost. The heat loss has therefore to be estimated (heat demand) or calculated (heat loss). Basic heat pump unit costs vary from £600 /kW for small heat pumps (3 to 5 kW)to £400 /kW at 10 kW heat output. Installation costs assuming no major changes to pipe work or heat distribution system would be around £1000 to £1500 excluding the hot water tank. Collector costs depend upon the location of the collector coil –
A modern UK home, size 80 m2, will have a heat loss of about 4-6 kW requiring a heat pump of a similar size. For an air source heat pump, the cost will be around £5,000 whilst a ground source heat pump will cost about £6,000 to £8,000 for a horizontal or vertical collector respectively. The choice of collector is dependent upon the available ground space – a length of some 10 m/kW and 20 m/kW is required either horizontally or vertically depending upon the annual heat demand of the property and the local geology/ground conditions. Heat pump systems are typically sized for a minimum outside temperature of -3ºC. If colder weather is experienced as occasionally happens in the UK, then extra heat could be provided by a wood fire in the living room or storage or convector radiators located in the bedrooms or bathroom. Hot water Most air/water or ground/water heat pump systems are capable of supplying hot water to 45C (or higher for some models). Appropriate hot water tanks are required. Running costs for space heating For a modern house of size 80m2, the heat loss will be ca 50W/m2 and with an annual heat demand of 11500 kWh which will increase the further north ones dwelling is located in Britain. Many heat pumps have the ability to control automatically a secondary heat source under extreme weather conditions.. For a heat pump whose ratio of heat out/energy in (coefficient of performance) is 4.0 the annual electricity demand is 2875 kWh. At 10.0 p/kWh (e) the annual cost is £287. By comparison, a modern gas fired boiler with an average efficiency of 80% requires an annual energy demand of 14400 kWh. At 3.0 p/kWh (g), the annual cost is £430. So for well insulated dwellings heat pumps will be cheaper to operate though there will be a higher initial cost. The actual payback time will be very dependent upon how the price of electricity is likely to increase compared with that of gas over the next 15 years. Grants, tariffs and tax credits The maximum grant for a ground source heat pump available under the low carbon buildings programme is £1,200 or 30% of the eligible costs. To be eligible to receive a low carbon buildings grant you must undertake a number of energy efficiency measures and you must use an accredited installer and an accredited product.
Details are given at the low carbon programme website see No UK utility currently offers a special tariff for heat pumps - however this situation could change in the near future as utilities realise the benefit of being able to run heat pumps as base load. No tax credit is currently available but VAT is only charged at 5% including installation for certain buildings including dwellings.
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