gas
because it can start fire witch is hot.
Home heating, Cooking, Heating water. Fuel for internal combustion engines. To name a few.
Usually gas or heatpump
d) hot-water heating system In a hot-water heating system, heat from burning fuel warms the water in the boiler. This hot water is then circulated through pipes to radiators or baseboard units in different rooms of the building, providing heat to the space.
Oil, natural gas, and propane
Electricity itself is not a fossil fuel but, can be generated by steam turbines and generators where the steam has been generated by heating water in fossil fuel boilers.
The source of heat created by burning fuel in heating systems is typically combustion, where the fuel is ignited and reacts with oxygen to produce heat energy. The heat generated from this combustion process is then used to warm up the air or water circulating through the heating system.
A hot water heating system should not lose any water unless there is a leak. The type of fuel used does not matter.
The best one I have used in the past is http://www.fuelstart.com
When a fuel is burnt and water is released in the liquid phase, the heating value is called the "lower heating value" (LHV) or "net calorific value." This measurement accounts for the energy released during combustion, excluding the energy contained in the water vapor produced, which remains in the gaseous state. In contrast, the "higher heating value" (HHV) includes the total energy released, including the condensation of water vapor back into liquid form.
The heating value when water is released in the liquid phase during fuel combustion is called the lower heating value (LHV) or net calorific value (NCV). It considers the latent heat of vaporization released as water transitions from liquid to vapor during combustion. The LHV does not include the heat energy that would be obtained from condensing the water vapor back into liquid form.
Most boilers combust some type of hydrocarbon fuel such as natural gas, heating oil, heavy fuel oil, coal, biomass, or petroleum coke. The fuel must either be stored on site or stored offsite and input by a pipeline.