  Common envelope evolution (CEE) physics plays a fundamental role in the
formation of binary systems, such as mergering stellar gravitational wave
sources, pulsar binaries and type Ia supernovae. A precisely constrained CEE
has become more important in the age of large surveys and gravitational wave
detectors. We use an adiabatic mass loss model to explore how the total energy
of the donor changes as a function of the remnant mass. This provides a more
self-consistent way to calculate the binding energy of the donor. For
comparison, we also calculate the binding energy through integrating the total
energy from the core to the surface. The outcome of CEE is constrained by total
energy conservation at the point at which both component's radii shrink back
within their Roche lobes. We apply our results to 142 hot subdwarf binaries.
For shorter orbital period sdBs, the binding energy is highly consistent. For
longer orbital period sdBs in our samples, the binding energy can differ by up
to a factor of 2. The CE efficiency parameter $\beta_\mathrm{CE}$ becomes
smaller than $\alpha_\mathrm{CE}$ for the final orbital period $\log_{10}
P_{\mathrm{orb}}/\mathrm{d} > -0.5$. We also find the mass ratios $\log_{10} q$
and CE efficiency parameters $\log_{10} \alpha_{\mathrm{CE}}$ and $\log_{10}
\beta_{\mathrm{CE}}$ linearly correlate in sdBs, similarly to De Marco et al.
(2010) for post-AGB binaries.
