  Let $G$ be a graph with $n$ vertices and $m$ edges. The energy $E$ of the
graph $G$ is defined as the sum of the moduli of the adjacency eigenvalues
$\lambda_{1} \geq \lambda_{2} \geq \ldots \geq \lambda_{n}$ of $G$: $$
E=\sum_{i=1}^{n}{|\lambda{i}|}. $$ We obtain new lower bounds on the energy of
a graph, which in various cases improve upon known results. For example, a
particularly simple and appealing corollary of our results is: $$ E \geq
\frac{2m}{\lambda_{1}}. $$ This implies a result obtained by Gutman \emph{et
al.} for regular graphs and is better for triangle-free graphs than a result of
Caporossi \emph{et al.}.
