Conventionally fractionated breast radiation therapy is delivered over 5–6 weeks. Randomised evidence has shown that hypofractionated whole-breast radiotherapy (HWBRT) over 3 weeks results in similar local control without increased toxicity. HWBRT is not standard practice in Australia for all eligible women. We examined the effect of using HWBRT (for eligible patients) on waiting lists and monetary costs. We identified factors associated with prescribing HWBRT. The Princess Alexandra Hospital Radiation Oncology Database was searched for all women with breast cancer treated with adjuvant radiotherapy in 2008. Included patients had undergone breast conserving surgery and had T1-2N0 tumours with negative margins. Women with large breasts and those receiving nodal irradiation were excluded. The outcome evaluated was fractionation schedule. Patient, tumour and treatment factors associated with the use of HWBRT were examined. The impact on departmental resources and health-care costs were calculated assuming the entire cohort received HWBRT. Two hundred seventy-nine patients met the inclusion criteria. Sixty-seven (24%) of these patients were treated with HWBRT. Compared with the conventionally fractionated breast radiation therapy group, the HWBRT group were older (median 69 vs. 54 years; P < 0.001) and more likely to have smaller tumours (12 mm vs. 15 mm; P = 0.02). Had all eligible patients received HWBRT an extra 14 patients each month could be treated and health-care costs would be reduced by 24%. HWBRT was more frequently prescribed in older women with small tumours. More widespread use of HWBRT would allow significantly more patients to be treated each month with considerable cost savings.