Perhaps you’ve replaced your old washer and dryer with new energy-efficient machines. Maybe you’ve added solar panels to power your home. But how energy efficient is hour house? A new software program from SolarCity will take homeowners on a self-guided tour of their energy use. It’s simple, quick and free for new SolarCity residential customers.

EnergyExplorer performs more than 100 million calculations per household to pinpoint energy inefficiencies. It then ranks possible improvements by costs and savings, a press release from SolarCity said. New SolarCity residential solar customers now have free access to the software and receive complimentary efficiency evaluations with their solar site assessments.

“Traditional efficiency audits generalize energy expenses, fail to pinpoint the source of problems and leave consumers guessing about possible solutions,” said Pete Rive, SolarCity’s co-founder and chief technology officer in a press release. “It’s like providing a symptom without a diagnosis.”

EnergyExplorer isolates the sources of energy expenses and provides specific solutions, along with the type of impact they could have on the home, he said.

The new software audit is faster than previous home evaluations, which used to take four hours and cost hundreds of dollars. The new software system taps into the Department of Energy database, a representative with SolarCity said. In addition to clear recommendations of what could be done to make the house more efficient, it also provides ways to get in touch with certified contractors for the specific upgrade.

Once a homeowner signs up for solar with SolarCity, an expert from the company evaluates the customer’s home. They record information related to energy use- like details about heating and cooling equipment, window types and insulation levels, while also evaluating it for solar. EnergyExplorer combines the evaluation data with local weather information, a three dimensional model of the building, and a Department of Energy database of equipment efficiencies, and then runs a simulation of energy use in the home. It creates a breakdown of energy costs and potential efficiency improvements including estimated savings and costs. The customer can then access a personalized website where they can take a self-guided tour of the results and select from the recommended improvements lists. They can choose to be contacted by a certified contractor for specific upgrades.

SolarCity has performed more than 16,000 energy efficiency evaluations since it launched its program in 2010. According to a press release the company analyzed data from past evaluations to determine the largest energy expenditures by region and inform targeted data collection that led to a simplified audit.