I would have used quality of life, not standard of living.
There are material solutions that have high initial capital costs, but there's also a ton of behavioral or lifestyle changes you can make.
One of the biggest is meat consumption. A calorie of meat has something like 10x the energy embedded it in as a calorie of vegetables. I'm not a vegetarian by any stretch of the imagination -- I just love ribs too much -- but I have significantly cut the amount of meat I consume to a few times a week. Helps you get more creative with cooking, opens up new tastes, and frankly, costs less.
Transportation is the other big one. I've started biking for my commute and it makes me feel great... I've lost weight and my commute just feels better than being stuck in a car or bus every day. That one could arguably be a lower standard of living (if you measure standard of living by the comfiness of your car) but in my opinion, definitely a higher quality of life (I'd rather be moving than stuck in traffic or crammed into a standingroom-only bus).
I would think that reducing consumption while maintaining standard of living would have high initial capital costs..