For renters
You can't replace the furnace, but you control a lot of the flow.
Bulbs
Swap old bulbs for LEDs and take them with you when you move.
Showerhead
A 1.8 gal/min head screws on by hand. Keep the old one to put back.
Thermostat
A night setback costs nothing.
Talk to your landlord
Share your card. It lists the source for every number, so it's a calm, factual ask about sealing or equipment.