Reducing fuel use for the heating of houses is key to meeting greenhouse gas emission reduction targets. This study constructs marginal abatement cost curves (MACC) of different technologies for space and water heating of houses in the county of Gwynedd in Wales, UK, and uses information provided by energy certificates to correctly assess the energy requirements of a house. This approach allows us to accurately predict energy consumption and identify potential ways to reduce demand. We then explore the costs and savings of a switch from systems using conventional heating fuel (e.g., gas, electricity, oil, LPG, and coal) to low-carbon technology such as PV, biomass boilers and heat pumps. Solar PV was the low-carbon heating technology found to be most cost-effective per tonne of emissions abated (£ / t CO2). A reduction in capital costs of low-carbon technologies could potentially make technologies such as heat pumps be cost-effective. Without any policy intervention, low investment and fuel cost of gas would make replacement with any low-carbon technology uneconomical. Emission savings in Gwynedd over 30-year period could be between 3.494 to 5.289 Mt CO2 if appropriate measures which cater towards reducing capital costs and/or incentivising the uptake of technology are adopted.