Let resistance of each wire be R. In series, $R_s = 2R$. In parallel, $R_p = R/2$. Heat produced H = V²t/R. The ratio $H_s/H_p = (V^2t/R_s) / (V^2t/R_p) = R_p/R_s = (R/2)/(2R) = 1/4$. The ratio is 1:4.