Conservation Services offered

[ev-supply]

A version of this used in the commercial world is called performance contracting. 

In your case, you could sign a contract with the homeowner that they will pay you their current annual utility bill for a set period, say three to five years.  Then you install and maintain new equipment on your dime, pocketing the energy savings.  It is easy to sell this, since the homeowner wouldn't have to buy new equipment or perform maintenance on it.  The profits generally come from the length of the contract.  It would also put the onus on you to really deliver on the promise of energy savings.

It sounds like it could be a good idea either way.