  The strikingly low luminosity of Uranus (Teff ~ Teq) constitutes a
long-standing challenge to our understanding of Ice Giant planets. Here we
present the first Uranus structure and evolution models that are constructed to
agree with both the observed low luminosity and the gravity field data. Our
models make use of modern ab initio equations of state at high pressures for
the icy components water, methane, and ammonia. Proceeding step by step, we
confirm that adiabatic models yield cooling times that are too long, even when
uncertainties in the ice:rock ratio (I:R) are taken into account. We then argue
that the transition between the ice/rock-rich interior and the H/He-rich outer
envelope should be stably stratified. Therefore, we introduce a simple thermal
boundary and adjust it to reproduce the low luminosity. Due to this thermal
boundary, the deep interior of the Uranus models are up to 2--3 warmer than
adiabatic models, necessitating the presence of rocks in the deep interior with
a possible I:R of $1\times$ solar. Finally, we allow for an equilibrium
evolution (Teff ~ Teq) that begun prior to the present day, which would
therefore no longer require the current era to be a "special time" in Uranus'
evolution. In this scenario, the thermal boundary leads to more rapid cooling
of the outer envelope. When Teff ~ Teq is reached, a shallow, subadiabatic zone
in the atmosphere begins to develop. Its depth is adjusted to meet the
luminosity constraint. This work provides a simple foundation for future Ice
Giant structure and evolution models, that can be improved by properly treating
the heat and particle fluxes in the diffusive zones.
