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- This looks wrong, but it's difficult to say why without seeing the data. MARKAL capital costs are probably in PJ/a, which should be interpretted as the capacity needed to deliver 1 PJ over a period of a year. So you need to figure out the energy required per house per year, and calculate capital cost per house from this. Then you need to assume the peak capacity of the heat pump (e.g. 6kW), and calculate cost per kW. This should be near £1000/kW.
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