Below is one of our posts from 2015 which is very relevant now that the gas moratoriums are starting.
Do I need an oil to gas conversion to be more efficient
The idea is that an oil to gas conversion will save you money in the operation of your system. This is true as gas is about 30% less than oil per BTU of heat. Therefore you can lower your bills just by changing the source of fuel. However, you can save even more just by looking at your existing system. By optimizing, upgrading, and updating your heating system with modern techniques and technologies you can save over 50% without converting to gas. These techniques should also be implemented if you choose to convert to gas anyway to see a savings of over 70%.
The boiler is just one part of a very intricate system. All parts need to be addressed to get the most out of the system.
Balancing steam and hot water systems, installation of outdoor and/or indoor reset controllers, variable frequency drive pumps, insulating of all piping, correcting sequence of operation, are just a few measures to name, making huge impact on efficiency and comfort of the heating systems.