As part of Concord's Green-Your-Heat program which ran in 2015, we got a home energy assessment and a rebate for cellulose blown into exposed, overhanging sections of the house. This has made the bedrooms more comfortable, and is saving heat.

Earlier in the decade, we installed spray foam on the roof of the attic. This has drastically reduced heat loss in the winter and heat gain in the hot summer sun. We love it. Since we implemented the roof insulation as part of a transition to electric heating, we were able to utilize a light plant rebate that helped to pay for a part of this project.

Going back further, we replaced old, inefficient windows and glass with high performance ones. The common understanding is that projects like these are usually not cost effective, but I can say it was worth it, in terms of comfort. We did not apply for rebates or other subsidies for this work. We may have gotten some tax breaks for adding foam board when we resided.

I recommend you schedule a home energy assessment to see what projects may be effective and if your home qualifies for rebates.

Two of our air conditioning zones went out this summer.  We decided to replace them with heat pumps. We couldn't be happier. In addition to the energy savings, they are much quieter than the air conditioning systems we had before, and the temperature control is much more precise. Also, while the installation cost was slightly higher than a conventional system,  because they use less electricity, and the relevant rebates, the increased cost will pay for itself in just a few years. 

If you do go this route, we would strongly suggest you look at a system like Bosch or Daikan that uses an inverter technology. As I understand it these systems, vary the level of the heating and cooling depending on the situation, rather than just being "on or off" like more traditional systems. These account for greater energy savings, more precise temperature control, and quieter operation.   

My oil heated home has four heating zones. A few years ago, Muirfield Mechanics installed an Air Source Heat Pump in the central living space which is the most used zone. To my delight, the system heats the central living space and travels up the stairs to partially warm that space as well-an added bonus.
Soon, I will consult the Abode coaches who have been hired to consult on heat pumps by our light plant. It may take me a few years, but I'd like to know what the best and most affordable strategy is for moving forward on using heat pumps throughout my home. My family and I will feel better knowing that our heating and cooling is all electric, running on renewable energy, and not contributing fossil fuels to the climate emergency.