I find that efficiency is bad on short trips, but on trips over 20 minutes long efficiency improves a lot. Not sure if the battery just needs to warm up or what

I find that efficiency is bad on short trips, but on trips over 20 minutes long efficiency improves a lot. Not sure if the battery just needs to warm up or what. I rarely drive that long so my lifetime efficiency is 20% worse than the EPA rating. There's also self-discharge and other consumption when not driving, which may be an even worse problem for EV efficiency. I wonder what percentage of total EV electricity consumption is wasted while the car is off.