Heat rises so a bottom supply will work best.
The most efficient electric hot water heater available on the market is the heat pump water heater.
One of the most energy efficient water heating methods is the heat pump water heater. This method is proven to be two times more efficient over the standard electric water heater.
Any heater that has the Energy Star label will be very energy efficient. The Honeywell eco line, for instance, are very energy efficient.
The question is better defined as "What the most energy efficient portable heater?" Because one would assume that you will want to be able to take the heater with you when or if you move.
instant gas
The most efficient heater for a water tank is a tankless water heater. It heats water on demand, only when needed, which can save energy compared to traditional water heaters that constantly heat and store water.
The most efficient electric water heater available on the market is the heat pump water heater, which uses electricity to move heat from the air or ground to heat water, making it more energy-efficient than traditional electric water heaters.
Vornado is the brand of heater that is the most energy efficient. If used properly, Vornado heaters can heat just as well as a larger heater, for a much lower cost. They are small, portable, and can heat large rooms. Some of them even have thermostats or timers to increas efficiency.
The perway space heater works best in a medium-sized room with proper insulation. It is most efficient when placed in a central location within the room, away from any obstructions that could block the airflow. Additionally, keeping the door closed to contain the heat can help maximize its effectiveness.
Oil-filled radiators are typically considered the most energy-efficient type of radiator heater. They heat up and retain heat well, providing a consistent warmth without constantly running, making them more energy-efficient compared to other types of heaters. Additionally, they do not dry out the air, making them a more energy-efficient and comfortable option for heating a room.
Check the code for your area. Most I have seen go through the ceiling.
I have no experience in this, however A. O Smith claims that there brand of gas water heaters are the most efficient. They also offer a hybrid water heater.