Winter is here, and our guide to portable heaters may help you stay warm and save big bucks in energy costs.
Of course, we are talking about portable electric heaters. In this guide, we look at three things Portable Space Heater
We are not covering gas, boiler/radiator, heat pumps, air-conditioning (just a mention), underfloor, etc. These require expensive capital outlays.
Most homes are poorly designed to keep heat in winter and out in summer. The ideal is an 8-10° temperature difference and to retain that cool/heat during the day/night.
Compare the inside temperature to the outside. If it is less than an 8° difference, you need to act. Why? Simple things can reduce heating or cooling costs by up to 40%.
The Australian Government has a great guide here, so here are a few points:
If you can get your thermals under control, it can mean only having to heat an area from 18° to 22° instead of 10°.
If you have a large room, the heater will valiantly try to heat it, especially the thermostat-controlled models, which keep going flat out, wasting energy and never reaching the desired temperature.
You need about 2400W per 20m3—the only issue is how long it takes to raise the ambient heat load to 22°.
Assuming electricity costs 40 cents per kilowatt-hour (kWh – 1000 watts per hour), that small, cheap, radiant bar heater uses 2000W per hour – 80 cents per hour!
Convection-style portable heaters radiate heat – hot air rises, and cold air falls. The problem with convection is cold air from around the room is drawn into the convex. If you tried to heat the whole 120m3 open plan area, you would need six 2400W heaters strategically placed, chewing up big $$$ per hour.
More efficient heaters use fans and oscillation to create a heat zone or microclimate. For example, the Dyson Hot/Cold fan/purifiers can heat a 45° cone-shaped area approx. 3 metres deep and 2 meters wide (15m2) using a fraction of the electricity. If you can reduce the area you heat, you will save significant dollars. The Dyson Purifier Hot and Cool Models have a 10-speed fan, variable oscillation angles and the Coandă effect (10x air multiplier) to blow air up to 37°. It is perfect to quickly (10-15 minutes) create a microclimate around the lounge couch and then gradually (over a few hours) warm a larger area. Flat out – fan speed 10 and 37° it consumes <2000W. The auto setting for 22° uses from 500-1000W to maintain that microclimate. You get air purification as a benefit.
Harvey Norman lists 91 portable heaters. These range from $39.95 for an 1800/2400W fan heater to $749 for a 2400W panel heater on castors. Note that 2400W or 2.4kW is the maximum you can plug into a power point. All too often, you can overload the circuit if you turn on a jug or toaster.
None can heat more than a small 20m3 room, but fan and thermostat models heat faster. Rule of thumb – fan heaters will do a better job and use less electricity.
These are no better than radiant electric – people believe they are more efficient – they are not and tend to be left on for far longer
The solution uses a fraction of the power to heat you to the temperature you want. Make sure you get one with auto-off.
These are just marketing hype to make you think they are for larger spaces. The irony is that the maximum wattage you can plug into a power point is 2400 (240V/10A). Get one with a fan if you want more efficiency.
These cost about $2000 to $3000 and have ratings from 1.0kW to 2kW—all capable of no more than 20m3. Some have a fan assist that can help spread the heat. None have a remote thermostat because it would show how ineffective this was. Instead, they measure return air or exit air.
You can get some with up to 3600W ($1.44 an hour), but they use 15W or a 3-phase point. Some also work off three-phase and can consume up to 4500W ($1.80 per hour).
An open fireplace is one of the less efficient ways to heat a room. Why? A lot of heat disappears up the exhaust flue, and there is usually no way to move heat around a whole room – you may be snug in front of it, but freeze three metres away. Not to mention the carbon and pollutants it can produce.
The best way to heat (or cool) an area is to install a split system air conditioner. There are way too many brands and models, but the trick is to match the room size to the kW capacity and then look for the most efficient models – usually the most expensive. These also have mandatory Energy Star ratings, so it is easy to choose. As a guide for a room (assumes 2.4m ceiling height)
There is an online room size calculator here.
The best thing about ACs is that they measure return air temperature and, when set to automatic, provide just enough heating (or cooling) to maintain that. Daikin has the Zena range of Coandă effect ACs that don’t blow on you but pick up to 10x times the air at the exit. These barely use .5kw at peak and over 8 hours average out at just over $1.00 All plug into a 240V/10A/2400W socket.
Thermal management is the priority. All portable heaters chew electricity, and at 30-75 cents an hour, that is a lot.
We want you to remember
Look at electricity cost over 1000 hours. That radiant 2-bar heater costs $720 – nearly twenty-four times its purchase price. The Dyson costs $150, and it pays for itself soon after. The Daikin Air conditioner costs $150 too.
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