Household Heating Efficiency: What Actually Reduces Energy Use

Heating accounts for the largest portion of household energy use in Ireland, and the systems that supply it vary widely—oil boilers, gas boilers, heat pumps, or solid fuel stoves. Each has a different efficiency rating, and that rating tells you how much of the fuel's energy becomes useful heat at home. A modern condensing gas boiler might reach 90% efficiency, while an older oil boiler could be 70% or lower. That gap is typically worth understanding before assuming any system is clean or cheap. Efficiency also depends on how the system is installed and maintained—a boiler that is well-serviced and properly controlled will perform better than a newer model that sits in an unheated garage. Realistic expectations matter: you cannot typically cut heating costs by half through insulation alone if the house has poor air tightness, and heat pumps require specific housing conditions to reach their rated performance. This page compares heating systems, explains efficiency metrics in plain language, and outlines where practical gains can actually be achieved. Each section includes specific constraints, examples of situations where advice changes, and practical checks that a household can perform.