Winter is coming – time to think about portable heaters (guide)

Winter is coming, 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

  • Types of heaters
  • Best places to use them
  • Efficiency – power use to heat a specified area

We are not covering gas, boiler/radiator, heat pumps, air-conditioning (just a mention), underfloor, etc. These require expensive capital outlays.

Why do you need a portable heater?

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:

  • Seal windows and doors to save 15-25% winter heat loss. Use some self-adhesive foam strips and door seals. It is the low-cost DIY instant fix
  • DIY fibreglass or aluminium, roof bats, or blow in composite insulation reduces heat loss through the roof by 25-35%.
  • Window coverings – blinds and curtains reduce 10-20% glass heat leakage

If you can get your thermals under control, it can mean only having to heat an area from 18° to 22° instead of 10°.

Room size must at least match the portable heaters capacity

If you have a large room, the heater will valiantly try to heat it, especially the thermostat-controlled models that 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 achieve 22°.

  • Small bedroom 3 x 3 x 2.4m = 20m3
  • Medium bedroom 4 x 4 x 2.4 = 40m3
  • Large bedroom 5 x 5 x 2.4 = 60m3
  • Open plan kitchen, dining, lounge 5 x 10 x 2.4 = 120m2

Assuming electricity costs 30 cents per kilowatt-hour (kWh – 1000 watts per hour), that small, cheap, radiant bar heater uses 2000W per hour – 60 cents per hour!

Here is where fan-forced heaters come in – create a microclimate

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 Model has 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.

Portable home heating – heater types.

Harvey Norman lists 94 portable heaters. These range from $29.95/$39.95 for an 1800/2400W fan heater to $629 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.

Radiant heaters

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.

TypeWattage (kWh)Running cost per hourSuitable for
Radiant convention heater 2-bar typically <$301800-240055-72 centsSmaller closed rooms to 20m3
Radiant convention heater 3-bar typically <$60Usually three settings
800/1600/2400
24/48/72 centsAs above but the advantage of selecting lower heat levels
Ceramic heater with thermostat <$301500W45 centsAs above, but thermostat can save a few cents
Convection heater with timer and thermostat <$60Usually two settings from 1000/2000W30-60 cents 
Oscillating fan element heater with thermostat <$302000W60 centsFans raise the temperature faster and then require less heat to maintain it
Tower fan heater with thermostat <$501000-2000W30/60 centsDyson style and the most efficient. Especially useful for microclimate areas

Bathroom heaters

Radiant ‘bathroom’ 1 or 2 bar strip heater <301200 or 2400W36-72 centsRoom size 10m3 When you are in a cold bathroom, running cost is not an issue
IXL-TASTIC heat lamp bathroom heaterEach lamp is 275W. Usually 2 or 4 lamp switchable8 cents per lamp or 32c for fourRoom size 10-20m3 As above, it feels hotter as the heats radiates downwards.

Oil-filled heaters

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

5 fin1000W30 centsThis power rating will take about three times as long as a radiant heater
11 fin2400W usually with three settings – 800/1600/2400W24/48/72 centsAs above

Heated throw rug

The solution uses a fraction of the power to heat you to the temperature you want. Make sure you get one with auto-off.

Heated throwTypically 150W with 3 to 6 settings and auto-off5-15 centsPersonal heating

Space or Infrared heaters

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.

Electric faux wood fireplaces

These cost about $2000 to $3000 with ratings from 1.0kW to 2kW – all capable of no more than 20m3. Some have a fan assist that can help to 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 ($1.10 an hour), but they use 15W or 3-phase point. Some also work off three-phase and can consume up to 4500W ($1.35 per hour).

Wood fireplaces

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.

Air conditioning split systems

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)

  • <20m2, 2-2.5kW
  • 20-40m2, 3.5-5kW
  • 40-60m2, 5-6kW
  • 60+m2, 7-9kW

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.

CyberShack’s view – portable heaters are an expensive band-aid.

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

  • Address thermal design first to reduce the heat or cooling load from ambient temperature
  • Heat only the area you need – create micro-climates
  • No radiant or oil heater that plugs into a 240V socket will heat rooms over 20m3.
  • Radiant heaters with a fan are more efficient
  • Coandă effect fan heaters like the Dyson are the most efficient

Look at electricity cost over say 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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