It is a water heater, not a hot water heater. There would be little point in using a hot water heater. I assume that is your point.
A combination boiler provide hot water to a central heating system whereas the multi-point water heater does not. The multi-point water heater provides hot water to multiple appliances or taps at the same time.
form_title= Tankless Hot Water Heater form_header= Save money with a tankless hot water heater. Do you need to remove an old water heater?*= () Yes () No Do you want an energy efficient water heater?*= () Yes () No Where will you be installing the hot water heater?*= _ 
THERE IS NO SUCH THING AS A HOT WATER HEATER.
Yes! Connect a garden hose to the output valve of the water heater and open the water heater valve to put hot water into the kiddie pool. This is the fastest way to warm a children's pool.
It's called water heater. There isn't a reason to heat hot water
The term "water heater" is non-specific, but may imply a domestic hot-water heater, when read in context. A "hot-water heater" is specifically meant for heating water for domestic use. A hydronic boiler is also a water heater, but the water is only used for heating the radiators or for heating a hot-water heater, but the hot water of the boiler is not released for domestic use.Depends as there is a water heater and then a booster which increases the temperature for mostly commerical applicatons thus your heating the hot water to a higher temperature and some call this a hot water heater instead of a temperature booster
Not significantly. Using less hot water in general will save.
A tankless water heater provides on-demand hot water. The following guide provides simple tips when installing a tankless hot water heater. A tankless hot water heater is usually mounted on a wall, near a fresh water source. Most tankless hot water heaters are installed next to the cold water tank, or the home entry point of a municipal water supply. Using a PVC bracket, attach the hot water system to the water supply. After attaching the intake, attach the water output to the adjacent pipe. Make sure all gas and electrical connections are secured before turning on the tankless hot water system.
This is actually the best installation in warmer climates. It allows installation close to services using the most hot water, while mitigating for the dangers of a hot water heater; they catastrophically leak, explode, etc.
It is just a water heater. People just say hot water heater without thinking.
new boiler and hot water heater
If you are using water and not steam there should be a temperature controller mounted in the side of the boiler, that is where the start and stop point of the boiler is controlled.