I had a tankless electric hot water heater, it was installed when the house was built and we kept it for around 10 years.
When it worked, it worked fine. However, it broke every 2 years on average and each time it broke we had to have the parts shipped to repair it, meaning no hot water for at least a week and one time it took 6 weeks until we had hot water. The unit just kept getting tiny little leaks in the body of the system which would short out the entire electric panel. Not in places you would expect to see leaks, but in the middle of the plastic body. We spend probably $2K in repairs for it over those 10 years. The heater itself was under a warranty, but the labor was crazy. They would ship us a single part and tell us try this and see if that fixes it. No? Ok, now we'll ship you another part to try.
I couldn't deal with it anymore. Last year we had a traditional hot water heater installed. If it breaks, I can get a new one immediately.
I will say that I've heard the gas ones are much better. If you can do gas, it might be worth considering. Do NOT do electric.
When it worked, it worked fine. However, it broke every 2 years on average and each time it broke we had to have the parts shipped to repair it, meaning no hot water for at least a week and one time it took 6 weeks until we had hot water. The unit just kept getting tiny little leaks in the body of the system which would short out the entire electric panel. Not in places you would expect to see leaks, but in the middle of the plastic body. We spend probably $2K in repairs for it over those 10 years. The heater itself was under a warranty, but the labor was crazy. They would ship us a single part and tell us try this and see if that fixes it. No? Ok, now we'll ship you another part to try.
I couldn't deal with it anymore. Last year we had a traditional hot water heater installed. If it breaks, I can get a new one immediately.

I will say that I've heard the gas ones are much better. If you can do gas, it might be worth considering. Do NOT do electric.