Worcesters oil-fired boilers are available in combi, regular and system models. We offer high efficiency Greenstar condensing models, which operate to at least 90% efficiency (compared with many older boilers that can be as little as 50% efficient). Greenstar condensing boilers deliver this energy-saving performance by recycling exhaust gases to extract and re-use latent heat - a highly efficient use of energy which also significantly reduces carbon dioxide in the atmosphere.