We are doing some renovations and my husband wonders while leveller is best?

http://www.popularmechanics.com/home_journal/tools/4308358.html

The best bet is to try different levels. I usually use a small one for the pocket, the 3 dollar ones, and then when I have a bigger project I use my digital one. So usually a couple can be useful depending on the project.

The compact laser level is the smallest laser level on the market. It has exclusive non-marring vaccum base and mounts to virtually any surface using AIRGrip. It does not require the use of pins, tape, or tacks to mount

The Stanley Laser Level Square projects both horizontal or vertical laser chalkline. 1/2 In. at 30 Ft. accuracy. It's 90 degree layout guide calculates and turns angles in 5 degree increments. It uses retractable push pins to mount to wall surface.