This paper presents an assessment of the energy and economic performances of air source heat pump (ASHP) and ground source heat pump (GSHP) compared to a condensing gas boiler for use in residential houses in the Republic of Ireland. This paper utilizes the When2Heat dataset consisting of synthetic national time series of both the heat demand and the coefficient of performance (COP) of heat pumps with considerations of different heat sources—air, ground—and different heat sinks—floor heating, radiator heating, and water heating. The comparison of different heating systems is conducted using life cycle cost (LCC) and life cycle savings method for 20 and 40 year periods on the Irish national scale and for an average Irish home. The LCC results on the national scale show that the ASHP and GSHP with different heat sinks result in different LCCs due to the different electricity costs caused by different COPs. The significance of utilizing real COP time series is demonstrated by the results of LCC sequence (which system has lower LCC). As this LCC sequence differs between an average Irish home and the Irish national scale. For 20-year LCC, the gas boiler LCC is still competitive compared to ASHP and GSHP, while for 40-year LCC, GSHP shows the largest savings. The incremental payback periods of ASHP and GSHP compared to condensing gas boiler are calculated. GSHP resulted in a shorter payback period due to high operating cost-saving. A sensitivity analysis with major parameters of the systems is carried out. The energy cost is the most sensitive item for most cases. The escalation rate is much more sensitive compared to the discount rate. The findings of this paper show that ASHP and GSHP are feasible replacements to condensing gas boiler.
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