Tendril, one of few companies that serves household energy consumption data to both utilities and consumers, has landed a fresh $30 million third round of capital led by VantagePoint Venture Partners. It plans to further expand its hardware and software systems and forge more partnerships with appliance makers and utilities. It will round out its staff with 25 new employees.

Most smart meter and smart grid companies only beam data back to the utilities they work with so that those utilities can better respond to demand, redistribute power loads and avert outages. Tendril’s Residential Energy Ecosystem operating system, on the other hand, presents this data in digestible form to the energy consumers so they can adjust their behavior accordingly. All of this information is displayed on a small monitor called the Insight that shows how much energy is costing a user based on current prices, in addition to other metrics. As of March, when the company released its own iPhone application, users can also view some of this information on their handsets no matter where they are.

A key part of the system is Tendril’s partnerships with appliance manufacturers, which allow homeowners to monitor exactly how much power their thermostat, refrigerator, washing machine, etc. might be drawing. The company makes a small device called the Volt (see right) that connects to appliances to track and control the energy they’re using. This way, with Tendril’s software, homeowners can define rules and standards — like a maximum energy limit during certain hours (much like a personal budget). They then receive an alert whenever a rule is broken and have the ability to correct the situation remotely.

While some of this technology is already being tested in pilot programs ranging from 300 to 50,000 homes, the company says it probably won’t see a broad commercial rollout until 2011.

Based in Boulder, Colo., Tendril competes with smart grid startups like ComVerge and Trilliant, but it is one of the best funded. It last raised $12 million in a second round of funding from RRE Ventures, Vista Ventures, Appian Ventures and Access Venture Partners. It has raised $50 million to date.