These 2 snazzy new fixtures do not allow hot water - or even warm! - to get to the washing machine. The gas heater fires up several times per minute, but the washer only intakes a small amount of water at a time. Although they are installed within 2-3 ft of each other, there is probably 5 ft of pipe between them. A sink that is half way between them gets water almost instantaneously.
I am willing to install a small electric tank for the washer if it would help, but I can't reduce the amount of pipe by much. Is it worth the money?? My only other option seems to be to leave the tap in the sink running while the washer is on. (I do 90% of my laundry in cold water, but now and then only hot will do the job.). Thanks.

some tankles water heaters come with a built in buffer tank to eliminate that very problem.

i would contact the manufacturer of you heater to ask their advice.
from their site...
"Built-in mini-tank eliminates the minimum flow requirement and the hot/cold/hot stacking effect when compared to regular tankless"