Nine states have signed a memorandum of understanding that says that heat pumps should make up at least 65 percent of residential heating, air conditioning, and water-heating shipments by 2030. (“Shipments” here means systems manufactured, a proxy for how many are actually sold.) By 2040, these states—California, Colorado, Maine, Maryland, Massachusetts, New Jersey, New York, Oregon, and Rhode Island—are aiming for 90 percent of those shipments to be heat pumps.