Energy efficient electric heaters
Do energy efficient electric heaters really exist?
Some will tell you that energy efficient portable heaters are the most efficient form of heating around - that they're 100% efficient, even 300% or 400% efficient for heat pump electric heaters.
Others will point out that most non-renewable electricity sources (coal, natural gas, nuclear) involve burning a fuel, and converting at best 45% of the heat produced into electricity, so that even with a 100% energy efficient electric heater you are getting only 35-45% efficiency from the energy efficient portable heater when total energy consumption is factored in. Even geothermal electricity only converts about 35% of its heat source into electricity. So unless your electricity comes from solar, wind, or hydropower, you can't come close to the efficiency of a typical modern forced air furnace.
What's the truth? The truth is that electrical heat is almost always the most expensive and least efficient form of heating (unless your electrical rates are heavily subsidized), and that people who are stuck with electrical heating systems are some of the most motivated at finding other ways to conserve energy, for example by improving sealing and insulation, in order to offset the higher cost.
As for energy efficient electric heater ratings (for example ENERGY STAR or the Canadian EnerGuide ratings), there aren't any. Since all resistance based electrical heater elements are close to 100% efficient, these agencies have not tried to provide ratings that would motivate you to choose one system over another.
So if you are looking for the most efficient electric heater, you can stop looking now. Instead, read below to find out what will make an electric heater the most effective for your needs.
How do electric heaters work?
Here's how most electric heaters work: an electric current is passed through a wire that provides an electrical resistance. This resistance converts all of the energy embodied in the electric current into heat. Any electricity passing through the resistance wire that isn't converted into heat would cause a short circuit. So most electric heaters are energy efficient electric heaters - 100% efficient in the case of heaters without a fan - in the sense that all the electricity input is turned into heat. When the fan is factored in the efficiency is still in the 95-98% range, as the fans consume very little energy compared to the kilowatts consumed by the resistant heating element.
However, bear in mind (as described above) that when electricity is generated, a large percentage of the original energy is lost during generation, and some is lost in transmission. For example, electrical generation from a heat source such as a fossil fuel is typically only 45% or less, and transmission losses range between 2 and 6%. So an 80% efficient natural gas furnace is truly 80% efficient, while a 100% energy efficient electric heater with heat coming from coal is at most 43% efficient.
The exception to this 100% efficiency rule for electric heaters is a heat pump, which is briefly described at the end of this article. Heat pumps can provide more heat output per unit of electrical energy input than resistance-based heaters, so this leads some heat pump marketers to refer to them as more than 100% efficient, but this is somewhat misleading.
Types of energy efficient electric heaters
Strictly speaking, any resistance-based electric heater is an energy efficient electric heater. But different electric heaters spread the heat in different ways, which can be more or less effective for the job at hand. So rather than speak of energy efficient electric heaters, we should perhaps speak of the effectiveness with which these heaters meet your needs.
A central electric heating system usually involves a forced-air electric furnace with ductwork and room vents, or a forced-air electric boiler with radiators in each room. For a forced-air electric furnace, a heating element heats air that is forced through the furnace by a fan, and the hot air is then pumped through ducts throughout the house, much as in a forced air natural gas furnace. For a forced-air boiler, the boiler contains a heating element that heats water which then circulates, either on its own or with the help of an electric pump, through radiators through the home. If you have one of these units you may find yourself paying a lot for your heating. Such units are often installed in houses that previously had a forced-air oil or natural gas furnace or boiler, and the installation can usually be attributed to a time period or jurisdiction (state, province) when electrical energy was substantially cheaper, per unit of heat available from it, than natural gas or oil.
The bad news for central electric systems is that you may be spending a lot more to heat your home than if you used natural gas, since electricity rates in most jurisdictions have been going up as state-owned utilities begin to apply more market pricing to electricity. The good news is that, assuming a natural gas line can be obtained for your house, the process of converting to a natural gas furnace or boiler should not be too intrusive - you already have the required ductwork or radiator system. You'll need to do an "Energy return on investment" or payback period analysis to figure out how soon an investment in a natural gas furnace might pay for itself, but chances are the payback will be within five to ten years.
You may be able to turn your central electric system into a more energy efficient electric heater system by adjusting the furnace fan to start blowing air at a lower initial temperature, and to stop blowing air after the heating elements stop receiving power, again at a lower temperature. These adjustments are recommended by heating experts as they allow heat to begin flowing through the house sooner, and more heat to be extracted from the furnace and delivered to the house after the heating elements go off. For more details see the section "Maximizing effectiveness in forced air heating systems" in the Canadian Office of Energy Efficiency article Heating with electricity.
A baseboard heater spreads heat using a combination of conduction and convection. Conduction is the transfer of heat from the heating element to the air immediately around it (from a heated surface to a gas, in this case air), while convection happens when the heated air, which expands and becomes lighter as it is heated, rises out of the heater and draws colder air in from below. Air currents resulting from this convection draw the heat up into and around the room where the heaters are located.
Baseboard heating is a more common scenario than central electric heating, for houses originally built with the entire house being heated by electric heating. Baseboard heaters are inexpensive, unobtrusive, and require no ducting. They do of course require additional electrical work but it is usually easier to run a few extra wires than add an entire ducting system when building a new home. Note that one drawback of a house entirely heated with baseboard heat is the tendency of moisture to build up on windows, as there is less circulation of the air within the house compared to forced air systems, and combustion-based heating systems (natural gas, oil) sometimes use internal air to feed the furnace or boiler, which draws out moisture. (See my article Energy efficient dehumidifiers for tips on moisture control.)
Movable energy saving space heaters can operate by convection or radiation. Note that movable space heaters are a major cause of home fires, causing up to 25,000 residential fires each year in the US according to the Consumer Product Safety Commission. So if you go with a movable space heater, be very careful to keep a close eye on it, and follow the product documentation to minimize risks. Also, note that energy saving space heaters plugged into ordinary outlets can draw a considerable amount of power - 1,000 to 2,500 watts depending on the model - so make sure your wiring and fuse or circuit breaker for that circuit is up to the task!
The two types of common movable space heaters are convection and radiative. As with all electrical heaters, both are 100% energy efficient electrical heaters, except that where a fan is involved efficiency is a tiny bit lower as the electricity driving the fan doesn't produce any heat (but does make the heater more effective at heating the desired area).
A movable convection heater is much like a baseboard convection heater, except that it may be enhanced with a fan to propel the heated air in a particular direction and improve distribution of the heat through the enclosed space. And of course you can move it to provide the heat wherever it's needed.
A movable radiative heater has a very hot heating element, usually enclosed in a glass tube much like an incandescent light bulb. Behind the tube is a reflective strip of metal which directs most of the radiative energy from the element out the front of the heater. This energy is in the form of infrared radiation (don't worry - it's perfectly safe!). Some of this infrared radiation is converted to heat when it strikes a solid object (a chair, a wall, a person), and some is reflected further. Eventually all of it is converted to heat.
Cold air passing by a radiative heater does not get heated by it. Only the solid objects that absorb the infrared radiation are heated. For this reason, a radiative heater may be a good choice for a cold room such as a garage or outdoor workshop, where you only want to heat the specific area of the room you are working in, and where insulation and weatherproofing may be poor or nonexistent. But be aware of the risks - a radiative heater can set an object on fire if the object is too close, is exposed for too long, and is flammable.
Efficiency of passive and active electric heaters
Although all resistance-based electrical heaters are close to 100% energy efficient electric heaters in terms of converting electricity to heat (remember, a small amount may be used by a fan blowing the heat off the elements), we can think in terms of how effective they are at getting that heat to where it's needed, and not sending it where it isn't.
The more passive an electric heater is - the more it depends on heat rising, or natural airflows in the room, to spread its heat - the more its effectiveness is subject to the characteristics of the room or house it is in, and its own location within the room or house.
For instance, if a baseboard (a passive source of electric heat) is located on an outside wall with poor insulation, that wall will get hotter than the ambient air of the room, and some of the heat will escape through the wall. In the same room, an active convection heater such as an energy saving space heater with fan, would not heat the outside walls nearly as much, because it propels its heat forward more effectively, and so there would be less heat differential between the inside of the wall and the outside, resulting in less heat loss. A floor vent for a forced air electric furnace would also result in less heat escaping from the walls, because the heating element is centrally located in a well-insulated furnace, and the floor vent is (probably) not running hot air against an outside wall.
Of course none of this would matter much if the walls were very well insulated - little heat would escape out the back of a baseboard heater, so nearly 100% of it would be available to heat the room itself, as with a floor vent or movable heater.
The most energy efficient electric heaters for keeping one person warm in a cold room are active heaters, either radiative or convection. For example, if you get cold feet when working in a poorly insulated den, a small ceramic heater at your feet may be all you need to work comfortably. (That and a sweater.) Heating an entire room when the room is seldom used, and only for short periods, is not as cost effective as on-demand spot-heating of areas that are too cold for comfort.
Electric heat and time-of-use billing: meet the storage heater
If your electricity rate depends on time-of-use (e.g. you pay more for electricity during times when everyone is using a lot, such as during the weekday when industrial users of electricity are big consumers, or on very cold winter nights when many homes are using electric heat), then the most energy efficient electric heaters, at least from a cost savings perspective, may be storage heaters that let you save up the heat produced during low-cost times, and broadcast that heat during high-cost times.
Storage heaters use a set of clay bricks, or other ceramic material, as a heat sink. These heaters can direct the heat from their resistance-based heating element either to the air (if heat is required, electricity is currently cheap, and no heat is stored in the bricks) or to the bricks (if no additional heat is currently required, the bricks can store more heat, and electricity is cheap). When electricity is expensive, louvers are opened to allow heat from the bricks to transfer into the air.
Storage heaters can have automatic or manual controls. Automatic controls allow you to set a thermostat and have the room heated at all times to the desired temperature, with the heater determining when to store heat, when to emit stored heat, and when to heat the room directly with electricity. On cheaper, manual models (which are less energy efficient unless you can master the controls and have the time to keep tweaking them), the heater determines when to charge up the ceramic material with heat, based on time of day rates, and you control when and how much heat is emitted. Automatic models are typically 15-20% more efficient than manual models, although that improvement will vary depending on how skilled the person using the manual control is at controlling it!
Energy efficient electrical heaters with storage capability can save you up to 30% over regular electric heaters if your utility offers substantially lower rates at night, and if you heat your house to a typical comfort temperature during the day. These heaters can store up enough energy for the higher-priced peak periods in as little as 8 hours of off-peak operation.
Since the cheapest electricity rates tend to be at night (except on very cold winter nights, when rates spike), there is less of a benefit to your using storage heaters if you don't require much heat during the day. For example, if the house is vacant all day on weekdays, you can use regular energy efficient electric heaters and a setback thermostat to keep the temperature considerably lower during the day, in which case there is less value in having storage heaters that emit heat during the day when little heat is needed. Still considering the low cost of individual storage heaters (as low as $200 for a one-room unit, plus installation and wiring costs), the speed with which they can charge up at night, and the fact that few people set their programmable thermostats to a large gap between vacant and occupied temperatures, these units are a sensible investment for anyone adding or upgrading electrical heaters in their home.
Pretend you have time-of-use billing!
Even if you don't pay for electricity on a time-of-use basis, acting as if you did is a good way to reduce the amount of greenhouse gases you contribute to the atmosphere. Why? Because the times of highest demand for electricity in winter, when electric heat is used, tend to be:
- During regular work hours, because industrial and commercial operations use a large amount of electricity
- During extremely cold nights, when everyone using electric heat has their heaters running hard to keep their houses warm.
During these peak times, the percentage of electricity added to the grid that comes from fossil fuels is disproportionately high, because coal and natural gas generated electricity are the most flexible in terms of being brought online on short notice to meet short-term demand. So if you heat your house a little warmer during off-peak hours, and let it coast down below the ideal temperature during peak hours, you'll reduce demand for fossil-fuel-based electricity.
Of course this depends on your having an energy-efficient storage system for your heat. At the very least, this would be a well-insulated house. There's not much point in overheating the house one hour to take advantage of off-peak electricity, only to have that heat escape before the next hour's out because your home is poorly insulated. Beyond a well-insulated house, more effective storage systems such as an electric storage heater (see above) or other passive storage (see below) can help.
Do-it-yourself energy efficient electric heaters for time-of-use scenarios
While I wouldn't recommend that you try to create your own full-fledged heat storage system based on the above principles - unless you're an engineer and an electrician - there are ways you can take advantage of the ability of masonry or water to absorb and then emanate heat. The two key points are to heat when it's cheap, and to build thermal inertia into your home.
Heat when it's cheap: set your home to be heated to higher temperatures when electricity is cheap, and lower temperatures when it's expensive. You can do this using a setback thermostat and a knowledge of the time-of-use periods from your utility.
Thermal inertia; give your home a high level of thermal inertia, by (A) insulating to the hilt to keep the heat from escaping, and (B) incorporating a lot of masonry or sealed liquid in its construction.
For example, if you incorporate a large masonry fireplace with a sealed wood-burning or gas stove into your living room, the masonry will help stabilize your indoor temperature by soaking up heat when it is cooler than the interior air temperature, and by heating the living room when the living room is cooler. You don't ever have to have a fire burning to take advantage of the fireplace's heat absorbing and emanating properties, but obviously fireplaces tend to be big partly so that the extremes of hot and cold that come from burning a fire and letting it burn down are evened out by the masonry.
Or, if you have to rebuild or add an interior wall, you can add to its thermal inertia by putting bricks, or 2-liter plastic drink bottles filled with sand in between the studs. (I don't recommend water, although it's easier to come by from sand, because you might drill or nail through those walls later to hang a picture, and you don't want a 2-liter water bottle popping on you behind drywall!) You can also fill plastic bottles with water and leave them under your bed or in other areas where they aren't in the way - if you don't mind the dust bunnies gathering around them!
One benefit of building thermal sinks into your home - whether formal ones such as a masonry wall or fireplace that is not touching an exterior wall, or simple ones such as 2-liter plastic bottles - is that they work both for heating and air conditioning. During the air conditioning season, you can cool your house to a lower temperature when electricity is cheap, and heat will be drawn out of the thermal sinks. Then during pricier times the thermal sinks will absorb heat again, reducing the heat load on your home.
And don't forget to leave the bathtub full after you're done your bath in winter - until the water has fallen to room temperature. There's no point in letting all that expensive heat go down the drain, especially if you heat with electricity.
Energy efficient electric heaters - choosing the right addition to your home
If you want to add new energy efficient electric heaters to your home you first need to determine whether you're going for built-in baseboard heaters, or portable electric heaters.
Built-in baseboard heaters
If your house is heated with electric baseboard heaters and you want to upgrade to more energy efficient ones, I suggest you look instead at other energy efficiency upgrades that can reduce the amount of heat escaping from your home - your baseboard heaters should already be at 100% efficiency (in terms of converting electricity into heat).
If you definitely want to buy new heaters (for example, if the old ones stopped working), then go for a storage heater. Even if you aren't paying time-of-day usage now, the chances are very high that you will be within the next five years. And the gap between peak and off-peak electricity rates will only get worse in the future.
Depending on the model, baseboard heaters can be controlled by a built-in dial thermostat and optionally a timer control, or by a wall-mounted thermostat (regular or programmable). If you do buy baseboard heaters make sure you go for the timer control or a wall-mounted programmable thermostat. Electric heat is too expensive for you to heat each room the same temperature all the time. With a timer control or programmable thermostat you can ensure that heat is reduced (or even shut off if it's safe to do so - no frost risk, or no water pipes or masonry) at times when the room is sure to be unoccupied.
Wall mounted electric heaters
We keep our heat quite low in winter - 66F - and get by comfortably with sweaters and slippers. But taking a shower can be a chilly process, at least until the hot water has fully kicked in. This Stiebel electric wall heater is the perfect solution. It can heat a bathroom or bedroom to a toasty temperature in as little as 5 minutes and it is a solidly built, German-manufacturered heater that takes no floor space and very little wall space because of its sleek design.
The Stiebel wall heater can be installed with less effort than a baseboard heater and its fan helps spread the heat very quickly. It also comes with a 60-minute timer so that if you just want to heat the bathroom during your bath, or the bedroom long enough that you can warm up under the comforter, you can let it run a short period and have it shut off by itself.
Portable electric heaters
You can't just look for the highest-rated portable energy efficient electric heater for that chilly basement room, back porch converted into an office, or spare bedroom over the garage. Why? Because, as I mentioned above, all electric resistance heaters operate at the same efficiency level. Instead, I recommend you decide (A) whether you can switch to a different form of heat, and if not, (B) what use of the room is driving the need for heat.
Switching to a different form of heat: If your house is heated by a forced-air oil or natural gas furnace, and there is one room that is not well heated, consider having an HVAC specialist look at improving the ducting to that room. For example, a couple of years before we bought our house, the prior owners added a kitchen extension, with a crawl-space underneath that was not insulated. They installed baseboard heaters to heat this space. After we moved in (and paid for one year's worth of electricity to heat that kitchen extension), we removed the baseboard heaters and had an HVAC company branch a circular duct pipe off the main basement duct, to direct heat up from a floor vent. This cost only about $200 at the time and based on the drop in our electricity bills after that first winter I would guess the renovation paid for itself in under three years. We also added as much extra insulation in the crawl space as we could to reduce the amount of heat escaping out the kitchen extension floor.
Another option is to improve airflow between the cold area and warmer areas of your house, so that you can draw warmer air into the cold room. Strategically placed fans can be useful in this case. For an unheated back porch that has been enclosed and converted into an 'indoor' room, there may be an old window between the main area of the house and the porch; opening this window when the room is in use will improve airflow.
How will the room be used? Decide if the entire room needs to be heated, or if you only need to heat a single area, based on how the room is used. Also decide whether the room needs to be heated a large portion of the time, or only occasionally. To heat a single area, a radiative heater or a small convection heater with a fan is the best bet. And of course if you're heating the room only occasionally, then an energy efficient electric heater is less of a concern than if you're heating it all the time. For continuous heat, you will save the most on your electricity bill if you focus on making the room as well-sealed and well-insulated as possible.
Heat pumps
A heat pump does not so much produce heat as move it from a colder (outside) location to a warmer (inside) location. A heat pump can be three or four times more efficient than an electric resistance heater in terms of how much heat you get for the electricity the unit consumes. You will sometimes see heat pump manufacturers refer to their heat pumps as 300% or even 450% energy efficient, which is misleading. Compared to an electric baseboard heater, the same amount of electricity used by a heat pump may, under ideal conditions, produce 3 to 4.5 times as much heat indoors. But they are not converting energy from electricity to heat - they are converting electrical energy to mechanical energy, and using this mechanical energy to move heat from a colder to a warmer location.
Another way to put this is that electric resistance heaters are 100% efficient all of the time at converting their electricity to heat, while heat pumps can appear to be 300% to 400% efficient, when compared to electric resistance heaters, provided the heat pump is operating under ideal conditions.
The "ideal conditions" that lead to a heat pump reaching 4 times as much heat output per unit of electrical input as an electric resistance heater, usually involve an atypically small differential between the indoor and outdoor temperature. Heating to 18C when the outdoor temperature is 12C (64F indoors and 54F outdoors) can get you to this level of efficiency. But if you heat your home to 18C (64F) when the outside temperature is -18C (zero Fahrenheit) you will not do any better in terms of heat output for electricity input than with an electric resistance heater. In fact, because of condensation that occurs on the heat pump coils at these colder temperatures, the heat pump must sometimes switch to cooling mode (cooling the indoor air so it can warm the coils) in order to melt frozen condensed water on the coils. In addition, for colder climates, it is important to install a backup heating source when installing a heat pump, so that when the outdoor temperature falls low enough that the heat pump can no longer supply adequate heat, or can no longer do so as efficiently as the backup source, the backup kicks in.
Obviously, the climate in many areas, or through the heating season for even moderately cold areas, falls between the two extremes of minimal heat differential (high coefficient of performance for an air source heat pump), and extreme outdoor cold (performance no better than electric resistance heating), so the relative apparent efficiency of heat pumps versus energy efficient electric heaters will vary.
Energy saving geothermal heat pumps work around this high-differential problem, by extracting heat from deep underground, where temperatures never fall much below 12C. Thus they can reliably deliver three times or more units of energy output in the form of heat, compared to the units of electric energy input, because the ground temperature, being very close to the desired indoor temperature, reduces this differential.
While air-source heat pumps might not be suitable as your only heating option in a cold climate, they are a sensible investment if you also need air conditioning. For example, some portable AC units, and some ductless minisplit air conditioners, operate as air conditioners in hot weather, and as air-source heat pumps in cool weather. Some can also act as dehumidifers, so you get three appliances in one!
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