谷期电费:50×(0.62×50%)=50×0.31=15.5(元),平期电费:50×3×0.62=150×0.62=93(元).峰期电费:182.9-15.5-93=167.4-93=74.4(元),峰期用电量:74.4÷(0.62+0.62×50%)=74.4÷0.93=80(度),用电总量:50+50×3+80=280(度),用阶梯电费标准电费总数:(280-260)×0.67+260×0.62=20×0.67+161.2=13.4+161.2=174.6(元).答:改用阶梯电价计算,5月份小明家将支付电费174.6元.