Government and private-sector lenders say energy-efficient building upgrades could pay for themselves if they were only easier to finance.

To that end, a state working group invited bankers, environmentalists and policymakers to Denver on Wednesday to discuss how state and federal money intended for the upgrades could better reach homes and businesses.

Gov. Bill Ritter called efficiency a key part of the state’s “new energy economy” and said funding must reach middle-income households that might otherwise not afford the upgrades.

Home and office improvements such as better insulation or rooftop solar panels can pay for themselves over the life of a typical home mortgage, but owners can seldom afford to spend five figures upfront to make the changes, so lenders’ assistance is vital to making those improvements, speakers at the event said.

States including California, Colorado, Maine and Michigan allocated millions of dollars in federal stimulus money for such financing efforts, but some other states have approached the idea skeptically.

Federal housing authorities also effectively blocked one method, called Property Assessed Clean Energy financing, which allows homeowners to pay for retrofits by deferring the costs to their local property-tax assessments.

Boulder County was forced to put its local PACE program on hold June 29 after mortgage buyers Fannie Mae and Freddie Mac opposed the plan over fears that home-improvement liens might take precedence over home mortgages. Statewide bills to create similar programs have stalled in the legislature.

Still, real estate and banking professionals stressed that property taxes are only one of several ways to fund the upgrades. Homeowners could pay off the initial costs through gradual payments on their utility bills, more one-time government rebates or loans from the secondary market.

Retrofit loans are more effective than one-time grants because they can continue almost forever, said Gilbert Sperling, the program manager for weatherization with the U.S. Department of Energy.

Banks and institutional investors are ready to add momentum to the financing push by backing those loans on the secondary market, Sperling said, but they are looking for more information and a larger pool of participants.