The mechanics differ a little by path, but the shape is easy to hold in your head. On the bundle path, you begin by booking an initial home energy assessment with an approved service organization, which sends a registered energy advisor to your home. You pay for that assessment upfront, and it produces an EnerGuide rating along with a tailored list of recommended upgrades. From there you complete at least two of those upgrades with participating contractors, book a follow-up assessment with the same organization, and then your advisor submits the paperwork. Rebate cheques, including the $600 for the assessment itself, typically arrive within about 60 days of approval.
The single-upgrade path is more direct, though the details vary by project. For a heat pump, you request the participating-contractor list, your contractor confirms your eligibility and installs the system, and then they submit the post-installation application on your behalf. For solar, your contractor sends in a pre-installation form and you wait for written pre-approval before anything gets installed, which protects you from spending money on a system that would not have qualified. For appliances and smart thermostats, you buy from any retailer and upload your receipt within 60 days.
One thread runs through all of it: the equipment has to meet the program's standards. Heat pumps, water heaters, windows, and doors are checked against ENERGY STAR certification and the qualified products lists maintained by Natural Resources Canada, so confirming your chosen model appears there is a small step that prevents a big disappointment.