Space Heater Efficiency Calculation: Formula & Equation

Table of Contents

Space Heater Efficiency_ A space heater is a device for heating a single, small area. Central heating is used to heat several connected regions, such as the rooms of a house. Space heaters are powered by burnable fuel (such as fuel oil, natural gas, propane, or wood pellets) or electricity. Portable space heaters are regularly electric because a permanent exhaust is required for heaters that burn fuel.

Space Heating

Space heaters transfer their heat only to the surrounding area. This is usually produced by heat radiation and partly by convection. They are typically used only for auxiliary heating. The following devices are among the most popular space heaters: tiled stoves, firewood space heaters, and residential biomass cookers.

Biomass has also been utilized in the past for cooking and heating. In some developing countries, cooking and room heating is still often performed with open fire sites. The resulting emissions risk both people and the environment. Advanced biomass space heaters have closed combustion chambers and send the exhaust gases to the outside. Nowadays, biomass can be combusted efficiently with low emissions using advanced burning systems. There are various criteria for discriminating between space heaters.

Differentiation Criteria For Biomass Space Heater

In the following, the differences between space heaters are discussed in more detail.

Fuel_ Normally, logwood and pellets are burned in biomass space heaters. Wood chips are only applied in larger applications.
Heat transfer medium_ it is a stove if the heat transfer medium is air, and it is a boiler if it is water. Both can be designed as space heating systems, but stoves are more common.
Installation type– Space heaters can be made industrially or assembled on-site, same as a tiled stove.
Storage mass– This is the structural storage capacity of the space heater by chamotte or soapstone etc. It shows how much heat the stove can store. The storage mass of the space heater can be low to medium or high. A high storage mass is known as a storage heating stove.
Feeding technology _The space heater can be fed both automatically or manually. Logwood is usually added by hand, and pellets are often added to the system automatically. We have different methods for moving pellets into the combustion chamber.
The operating time_ The operating time is the duration of the ignition and recharging itself. Firewood space heaters and residential biomass cookers have an extended operating time; on the other hand, a tiled stove has a short operating time. A tiled stove regularly takes about an hour to ignite, and the heat output remains up to 12 hours.
Heat transfer _The heat transfer method can be radiation or convection.
Combustion chamber _The combustion chamber can be constructed of metal or ceramic. There are also ceramic combustion chambers with a limitation for the secondary air supply. For metal combustion chambers, there are versions with and without a shelter plate.
Draught conditions_ The draught can be evoked by a draught fan or naturally.
Grate _Space heaters can have grates. Also, the position of the grate can be changed. In the model of flat firing systems, the typical fuel quantity is 2-5kg, while far more fuel is common in the model of fill firing systems.
Combustion principles _There are four different types: updraft combustion without the grate, updraft combustion with a grate, vertical downdraft furnace, and lateral downdraft furnace.

Space heater Efficiency — Combustion principles for a wood-burning furnace (Reference: etipbioenergy.eu)

Types of Biomass Space Heaters

Based on the number of differentiation criteria, there are lots of different varieties of space heaters. The following, there is a short summary:

Open fireplace: The combustion oxygen is drawn directly from the room, and the quality of the combustion is poor. The heating capacity is usually less valuable than the view of the open flame.
Closed fireplace: Open fireplaces can be retrofitted to enhance the combustion quality. Most of the heat is transmitted by heat radiation.
Firewood space heater_ These stoves regularly have a viewing window and an excellent flaming quality. The heat is emitted by both radiation and convection.
Storage heating stove_ These stoves have a high storage mass to save heat from combustion. They can produce high amounts of radiant heat. They use the upper combustion principle.
Tiled stove_ This sort of stove is assembled on-site and needs expert knowledge for installation. It has a high amount of storage mass. The operating time is short and uses radiative heat transfer.
Residential biomass cooker_ This kind of heater is used for heating and cooking. Different combustion principles are possible. They are also intended to work as boilers.
Space heating boilers_ These units are also proper for heating adjacent rooms. They are hydraulically united with the heating system and have a heat exchanger. Space heating boilers can provide hot water too. The other name for them is extended space heaters.

Types of Electric Space Heaters

Space heaters are powered by electricity or the combustion of ignitable fuel. Combustion space heaters burn fuels, such as natural gas, propane, kerosene, or wood.

Electric space heaters fall into three main classes:

Convection heaters carry electricity in a heating element, causing the part to become hot. The elements are composed of both metal and ceramic, and the process is known as joule heating. Heat is transferred to the surrounding by convection. Some heaters include a fan for increased air circulation, while oil-filled space heaters do not have fans.
Infrared heaters pass electricity in a conductive wire and heat it. Most of the energy is radiant heating rather than convection. The hot wires emit infrared rays, which convey heat to solid surfaces rather than the surrounding air.
Heat pumps have the same process as refrigerators and air conditioners but in a reverse cycle. Convective and infrared heaters produce heat from electricity, but heat pumps just move the location of heat. Heat pumps transfer heat from the outside of a room to the inside, warming it. Many heat pumps can work reversibly and cool the room by pumping heat out.

What are the Differences Between Central Heat and Space Heaters?

Compared to central heating units, these kinds of heating devices are easily portable and smaller. Space heaters may need heat transfer ducts, but they can work on the same energy sources as central heaters.

Among the different types of space heaters, versions that rely on combustion are the most dangerous and the least eco-friendly to use. Combustion heaters have the most significant risk of causing fires in houses. Plus, combustion releases hazardous types of emissions into the air.

Homeowners are advised to have fire detectors placed in areas where the space heaters will be installed and used. It is better to look for a space heater that can turn off automatically when the unit accidentally fails. You should also avoid using a space heater with an extension cord. Space heaters usually use around 1500 watts, and by using an extension cord, you are putting a significant load on a single socket.

Electric space heaters that provide radiant heat are the most efficient types and are good options for warming up a room.

Convection heaters are other types of space heaters that function by warming up the air in the room. Both radiant and convection heaters fall under the same price range.

Some people think that buying or using space heaters would help them to bring down their energy costs. They are indeed helpful devices, but they are not a practical choice in every situation.

There are several factors to consider when picking between space heaters and a central heating system. The important one is the size of the place being warmed up.

If you only want to warm up a few rooms in your home, a space heater may be a more practical option. Space heaters consume less energy compared to central heat. Still, they are not as efficient as space heaters. As such, possessing a space heater in every room in the home and turning them all on will only cost you more, not less. Newer designs are more energy-efficient than older ones. If you find out that your central heating system is no longer providing the same heat as it used to, have it checked for probable issues or consider having your heater repaired or replaced.

Space Heater Efficiency

Electric and gas Space heaters have different heating rates and efficiency and should be discussed in a different way. Usually, gas heaters have less efficiency, but the gas charges are much less than electric bills.

Electric Space Heaters Efficiency

Electric heaters are all regarded as 100% efficient because they convert all the electricity into heat, but this does not indicate they are cheap to run.

All electric-resistance heaters are 100 percent efficient because there is no energy loss through ducts or combustion. It should be noted that some space heaters produce heat more quickly or are more concentrated compared to others. Also, utilizing an electric-resistance heater to warm the entire house is usually more expensive than using other methods, like a heat pump or a natural gas furnace.

For calculating the running cost, we need to know the power rating of the heater, given in kilowatts (kW). The higher the power rating, the more energy will be produced, but also the payment will be proportionally higher.

The chart below shows typical running costs for electric room heaters. Charges are for heaters on the highest setting and producing heat for the entire hour. However, some heaters have a thermostat and automatically turn off when the desired room temperature is reached, meaning in reality, the payment will be lower over several hours.

To calculate the costs yourself, times the heat output of an electric heater by the electric kWh unit cost. Electric room heaters are all costly to run and not suitable as primary heat sources. You should choose the type of heater depending on how you plan to heat the room because otherwise, you may have a high operating cost while not feeling an increase in comfort. Halogen heaters are the cheapest radiant heaters because of having a low power rating (but also produce less heat). At the same time, oil-filled radiators are often the most affordable convector heater because there is a thermostat to control the temperature.

Generally, if you have to utilize an electric room heater, use it only when it is essential and consider the following suggestions:

Use a timer if it has one; if not, you can obtain a time switch for the plug from a tool shop.
A thermostat will decrease running costs, though how much it decreases depends on many factors, such as room size, insulation, and making sure the thermostat is not turned up too high.
Avoid using heaters for long-duration, especially at peak hours if you can. It’s better to apply night storage heaters that are charged during the night.

Gas Space Heater Efficiency

Gas heaters are not the same as electric heaters in their efficiency because not all the gas is transformed into heat output into the room (some energy is lost as exhaust gases, moisture, and light). However, the gas we use in these systems is around three times cheaper than electricity, meaning that the operating cost is often comparable.

We can run gas heaters on mains gas or LPG (liquid petroleum gas), also recognized as bottled gas. Suppose you are thinking about purchasing a gas heater. In that case, you must check current safety regulations as some fixed heaters need flues or chimneys to vent combustion gases and moisture out of the building. Portable gas heaters don’t necessitate flues, but you must make sure the flat is well-ventilated. Otherwise, there is a danger from carbon monoxide, while the water vapor gas heaters can cause condensation and, without ventilation, it can lead to dampness and mold problems.

Gas heaters are available in the market with various heat output ratings and efficiency ratings, which we should look at in conjunction with each other. Heat output is a parameter to indicate how much heat will be provided in the room. If you have two heaters with the same heat output, the heater with higher efficiency will be more economical to run compared to the heater with lower efficiency. It is just because it will consume less gas to produce the same amount of energy.

The table here calculates the running cost for heaters using mains gas and LPG, based on various heaters’ average heat output and efficiency ratings. Actual payments will vary, but what’s essential is comparing them with each other. These statistics are based on the heaters while they are on full power for the hour, without thermostatic control.

The following table shows the average running costs for a range of gas room heaters. Again, the exact costs will vary if gas prices change.

To calculate yourself (output ÷ efficiency) x 100. Multiply the result by your gas kWh unit cost.

Central gas heating is typically the best way to heat your home if you use mains gas. Today there are boilers with an efficiency of around 90%. It is better to use the thermostatic valves on radiators to adjust the heat rate you want in each room.

How Can Control Systems Affect Efficiency?

Control systems are essential because it provides possibilities to manage heating with better precision which will help to minimize energy consumption and running costs. This is why electric heaters with advanced controls are often considered to be more efficient than those without.

Some key control characteristics you should care about when buying an electric heater include:

Precision digital thermostat

You can constantly monitor the room to keep your desired temperature setting, presenting accurate readings with slight fluctuation. It won’t shift from your set temperature, so you don’t need to bother yourself with energy waste due to overheating your home.

24/7 programming

Provides the ability to set up a heating schedule to balance your routine, so you only heat your house when it’s required, for example, at the night and on weekends.

Open window detection

Senses any unexpected drop in temperature and temporarily switches the heater off until a steady temperature is reached. It is ensuring heat isn’t wasted through open windows or doors.

Energy usage statistics

It is a function that makes it simpler to stay on top of your energy consumption so that you can understand the consequences and where it needs to change.

WiFi control

Allows for higher control that provides you access to many features and lets you program your heating with your phone or tablet. As long as you use the compatible app downloaded and access the internet, you can handle your heating with no concern about where you are in the world. So, you never have to worry about wasting energy heating your residence at the wrong time.

Yes, all-electric heaters are relatively efficient at the point of use, but you should not expect that they’re all the same. Programming and heating technology offers a lot of efficiency improvements, so it’s worth keeping this in mind when it comes to buying your next electric heater.