Over　the　last　two　decades,　the　residential　building　sector　has　been　one　of　the　largest　energy　consumption　sectors　in　New　Zealand.　The　relationship　between　that　sector　and　household　energy　consumption　should　be　carefully　studied　in　order　to　optimize　the　energy　consumption　structure　and　satisfy　energy　demands.　Researchers　have　made　efforts　in　this　field;　however,　few　have　concentrated　on　the　association　between　household　energy　use　and　the　cost　of　residential　buildings.　This　study　examined　the　correlation　between　household　energy　use　and　residential　building　cost.　Analysis　of　the　data　indicates　that　they　are　significantly　correlated.　Hence,　this　study　proposes　time　series　methods,　including　the　exponential　smoothing　method　and　the　autoregressive　integrated　moving　average　(ARIMA)　model　for　forecasting　residential　building　costs　of　five　categories　of　residential　buildings　(one-storey　house,　two-storey　house,　townhouse,　residential　apartment　and　retirement　village　building)　in　New　Zealand.　Moreover,　the　artificial　neutral　networks　(ANNs)　model　was　used　to　forecast　the　future　usage　of　three　types　of　household　energy　(electricity,　gas　and　petrol)　using　the　residential　building　costs.　The　t-test　was　used　to　validate　the　effectiveness　of　the　obtained　ANN　models.　The　results　indicate　that　the　ANN　models　can　generate　acceptable　forecasts.　The　primary　contributions　of　this　paper　are　twofold:　(1)　Identify　the　close　correlation　between　household　energy　use　and　residential　building　costs;　(2)　provide　a　new　clue　for　optimizing　energy　management.