Make sure you weatherproof your home
This is a reminder that heating and cooling are definitely one of the most expensive and hardest to predict when it comes to costs, so making the right decisions might come with the best return on investment in the long run.
If you want to cut the energy costs as best as you can, you could always use the thermal/light blocking curtains, but also the block drafts, and learn to live with warmer temperatures during summer and cooler ones during winter.
Of course, you can do that by wearing the appropriate clothing. You could also get an energy audit, and the majority of states have all kinds of rebates for things, such as encouraging green and smart energy consumption.