Think of it in terms of economics. If new buildings can do whatever, it will increase the demand for both (clean or dirty) electricity and natural gas. If they

Think of it in terms of economics. If new buildings can do whatever, it will increase the demand for both (clean or dirty) electricity and natural gas. If they can only install electric heating/cooling, then only the demand for (clean and dirty) electricity increases. So this law indirectly promotes the clean electricity industry.