Tankless or "demand" water heaters are a useful energy efficient alternative to having a tank water heater. It is a smart alternative because it heats up the water as the sink, shower, or other hot/cold water using device needs it instead of having to fill up the whole hot water tank which saves you a load of money.
A tankless water heater is much more efficient as it "flash" heats the water.
It depends on usage.
Take shorter showers, or get a tankless, "on-demand" water heater that heats the water as you use it.
1- Is the piping insulated2- When was the heater serviced3- Is the heater properly sized for the fixture unit demand
It is not the square feet that determines the size water heater you need it is the demand. The more people who live in the home the higher the demand on the water heater to produce enough hot water. 1-3 people requires a 40 gallon water heater 4-6 people requires a 50 gallon water heater Of course you can make do with a 40 gallon water heater with a family of 4 or more but you will at times run out of hot water. Even if there are only 1 or 2 living in the home do not buy a 30 gallon water heater. You save very little money and may run out of hot water. But at least a 40 gallon.
it puts cold water in and pushes hot water to the top
At current gas prices they cost less to use and a gas heater gives you a much greater supply of hot water on demand.
The top rated water heater would depend on the type required. Gas powered, Electric powered, on-demand, solar, tankless...there are many options these days.
If an instant, on demand water heater is to expensive or for some reason not an option for you, look into solar.
Usually there is a heater that warms the tank on purpose.
The purpose of a heater is to heat up the room when it is cold; by using gas
Yes, that is easily done, but will it cope adequately with demand ?