Akeena Solar, a Los Gatos, Calif. installer of solar power systems, said it raised about $4.1 million from a private investment.

The cash is to help it keep up with new competitors such as SolarCity, and comes at a time when the solar sector is growing rapidly.

Akeena is already public, and so the private investment is called a PIPE (Private Investment in a Public Entity).

The Westly Group, run by former state controller Steve Westly, also invested.