One of the most important parts of the sales cycle remains overlooked. It’s imperative that you “circle back” to every one of your customers and ask them how it went.
Start with the basics. “Are you happy with the installation?” Then, “Did we deliver everything that we promised when you first approved the project?“
Lastly, “Is there any benefit you recognized that we didn't talk about, something beyond the obvious utility savings that you're seeing in the wake of the installation?"
The answer to that third question is very likely gold. They might tell you a compelling story of non-utility-cost financial or non-financial benefits that they’re now enjoying thanks to your project. If so, you could say, "I would love to share that with others who are considering working with us. Do you mind if I quote you on that?"
If you get this kind of information you could use it for every additional sales call you make. Think about drawing concentric circles on a map, each one around a successful installation. From there you can find others who haven’t yet received those newfound benefits and contact them, using your past client’s positive experience as your opener.