Energy Efficient Laptop for DE

Hi there, quick question for those of you more computer/tech savvy than I:

Assuming you wanted to play AOE2 DE on a laptop in an environment with limited power supply, what type of laptop would you recommend I buy? I do not care about higher/advanced graphic settings, I already play at low settings on my desktop.

Assuming there will be limited recharging available for a laptop, what model do you recommend that can run DE the longest before it needs to recharge? Also, does the amount of power it draws from a battery (assuming a portable power bank, not a wall charger) for a full recharge vary depending on the laptop model? How many hours would I be looking at for DE gaming before a full charge runs out?

To clarify, graphic settings and looking pretty is not important, but game play being smooth and no lag is very important.

Note I will be buying the laptop specifically for this purpose, so feel free to recommend any websites or models.

Thanks!