Air Conditioner as Heater for Winter

JohnnyB.Cheap on 09/05/2023 - 08:27

With this recent cold snap the $20 kmart heater from 10 years ago has come out again and is looking to cost us $300 this winter. My partner has floated the idea of instead of $300 spending on running the thing we spend ~$1700 (unit+installation+energy) to switch to a reverse split system. While not quite a saving, we are living quite modestly and with the El nino incoming it could be a good time to get Aircon in before the return of 45 degree summers. I also refuse to use fossil fuels to directly heat my home.

I am approaching this from a QoL perspective, rather than spending the least amount possible. That is to say, I'm happy to spend upfront to save long term.

Owners of Aircon units, I have some questions…

  1. Do you use it for heating over other devices, if not why not?
  2. Does anyone know the decrease of efficiency that having the outdoor unit in sunlight would cause in summer? Should it govern our installation location?
  3. There are general rules out there for what kW rating for what m^2 . For people that chose the bottom end of the range do you regret it or is it serviceable?
Electrical & Electronics Air Conditioner

Comments

  • thatonethere on 09/05/2023 - 17:55
    +1

    The reverse cycle is good - but on some canberra winter days it's -5 outside so the poor unit struggles through defrost cycles and generates no heat inside. When it gets cold I use a Nobo panel heater to heat up the house and leave the RC for later in the day.

    Supposedly the unit was for cold climate.

  • Miami Mall Alien on 09/05/2023 - 18:32
    -8

    It's amazing that this is actually a question on these forums.

    IQ points must be dropping faster than the BTU output of the OP's Kmart heater in winter.

    • JohnnyB.Cheap on 10/05/2023 - 07:38

      Please feel reply with by what percentage direct sunlight degrades the efficiency of an air conditioner if your IQ is high enough! :)

  • Danstar on 10/05/2023 - 08:57
    +1

    Split systems all the way.

    I have gas ducted; which I only use for 20-30 minutes in the morning to warm up the house quickly; otherwise I just turn on the main split system and that keeps the house at a consistent warm temperature and my power bills aren't that much different. I notice my gas bill is way higher if I use the gas heating more often

    • The tiger on 10/05/2023 - 09:26

      Yes, I notice my newly installed gas heater, a Brivis 6 stars , uses a lot of energy, so much so that I prefer to use the Kmart electric heater instead while 2 of us watching TV in our living room. Do not know why?

      • Danstar on 10/05/2023 - 09:45

        Ducted? Throughout the whole house?

        That would be why if you answer yes to those 2 questions.

      • Nebargains on 10/05/2023 - 20:37
        +1

        That doesn't sound right?

        We have a brivis 6 star gas ducted heater heating a 4 bedroom house and our bills are fine. Really shouldn't be using much electricity, should be using more gas.

        Anyway, didn't realise people like having split systems in every room, ugly as, ducted all the way for me. We have it fully programmed for different temps at different times on different days, once the house gets up to temp it only comes on briefly for short periods of time and it's just nice and comfortable inside. Doesn't feel hot or stuffy and no stupid split systems in all the rooms.

        • The tiger on 11/05/2023 - 08:20

          Nebargains, hi, how much it cost you in winter one month? . Mine was around $300.00 p.m. for two of us senior couple. Do you think it was excessive? Winter months are approaching next month and I begin to worry as how to meet the bills. At present we are using Kmart heater to warm us up in our living room.

        • Danstar on 11/05/2023 - 14:33

          I meant the gas ducted would cost a lot more than using electric split systems

  • Sega on 10/05/2023 - 10:20
    +3

    SS RC AC is the go. I used to do admin work for an electrician business who installed a lot of ac units, so I learnt a lot about the benefits.

    I have a power pal device to measure my electric usage. Monday 08 May I turned on the AC around 6pm, off around 10.15 when to bed around 11.30 (when I finally felt cold). The daily cost on the Powerpal was $3.54.

    Tuesday 09May I came home, was in bed around 6.30 pm after heating up leftovers in the MW, not lights, no AC, No TV. The daily cost on the powerpal was $2.08.

    The AC would have been the biggest contribution to the $1.46 difference day on day.

    If I go away from home the background stand by elec cost for a 24 hr period is $1.90-$2.00. Fridge, NAS, UPSx2, couple of clocks, MW, Toaster. Alexa and assoc speakers, Google home, Phillips Hue, modem. I have Kasa switches on 6 outlets which have entertainment and appliances connected.

    I’ve got a good elec deal thru to aug 2023.

    Get a really good installer, big is not better, ie size he ac to the room correctly. A RC in each room will be better that ducted. You will only need a 2.5 kw in a BR. (Which is an overkill unless it gets hot anyway imo).

    Stick to Fujitsu, Panasonic, Daikin if you can afford, Mits elec before Mits Heavy Industries (MHI).

    The rest might be TLDR but is back ground context. The gist is all above.

    I’m single live alone, 60yo.

    I’m in SW Vic, winters are overcast and wet… sometimes cold but mins not usually under 0, maxs common 10-15.

    I have a Ngas space heater (used rarely) and a 7.1kw AC in lounge. 60s BV, 3br, sort of open plan as in can leave lounge from one double doorway, walk down hallway around to kitchen and back thru to the lounge. The air can circle. Ceiling fan in lounge.

    The climate here is such that I rarely use the AC in summer for cooling. 2-3 days is rare, a few hours one or two days is the norm for me.

    Re winter, it’s used for heating currently I have it running set at either 25 or up to 27
    deg for a while if I have been away, the ambient temp in the house can drop to around 13 if I’ve been away for a day or 2. This gives me a temp of 23 in other areas of the room (where I sit etc). I’m not using a throw rug yet to sit and watch tv, and I have old alum sliding windows so they are a bit leaky air wise. I curtain them well, and have insulation in ceiling. The biggest issue I have are air leaks and thin original carpets on stumped timber flooring. It can be windy here.

    Th reason i have it up so high I would say is because it’s likely lower on gas that optimum. I won’t go into this as I know why this would be. But to me the cost is minimal.

    I would usually have it 22-25 and sit under a throw rug and wear warmer clothing close a door … it’s comfortable at that.

  • Kazzamc on 10/05/2023 - 11:03
    +2

    There’s a fb group “My Efficient Electric Home”. They are very pro using split systems for heating the home. It’s a really interesting group with some very knowledgeable people in it.

  • Waltervp on 10/05/2023 - 11:11

    I suggest you get a good quality 7kw reverse cycle inverter heat pump in a central part of the home which is hopefully your living room/ kitchen area, and have anti condensation ducting system installed running to all the other rooms. The ducting may cost you $1k and if your get a roof heat exchange unit that takes heat out of the roof cavity on sunny winter days, an extra $1k.

    We had this done to a home and because a very small fan sucks heat from the living area and pumps it to the test of the house you will have no more moisture in the home, even bathroom hardly fogs up, and your house will be marginally heated by it. Certainly not as cold as it used to be, though it is definitely not central heating because it doesn't take much heat from your living area, hardly noticable. I had expected large electricity bills when partner kept temp on 20 day and night (old home with relatively poor insulation) but it really wasn't excessive nor much more than before. Can highly recommend that to reduce mould issues, and keep whole house at livable temperature. Before it was freezing cold in the unheated part of the home in winter!

    • JIMB0 on 10/05/2023 - 11:39

      That's an interesting idea. We've got a split system in the main living area of the house which will heat most of the house eventually. Would be good to have system like this help distribute the heat especially with doors closed. Have you got a link for information and examples?

  • 2esc on 10/05/2023 - 12:57
    +1

    Have you gone right round the house and checks for draughts you might be surprised where you find them.

    Have you been in the roof cavity? You need to look yourself. My house the previous owner got the insulation grant years ago only a third of the house had insulation laid out a heap of bags of insulation still unopened i ended having to lay out and buy more as there wasn't enough. A lot of insulation installers also dont go right to the edge of the roof as its time consuming as thevroof is so low.

  • pebee47 on 10/05/2023 - 14:26

    I installed ducted reverse cycle air to whole house with individual rooms flow control. Also upgraded solar panels which means I now have a smart meter for lower costing power. Can heat/cool house during cheaper times of day which can carry over into peak power periods. I still load plenty of electrons back into the grid, so looking at hot water heat pump to soak up more of the solar power.

  • Trekky on 10/05/2023 - 17:04

    I use my ducted aircon for heating - I have 4 zones (each of the bedrooms x 3 and the kitchen/loungeroom area)

  • us3rnam3tak3n on 10/05/2023 - 18:59

    I have 3 small (3.2/2.5kW output) units in individual rooms and a larger (~5kW I think) mostly powered by solar. I've only had them since spring and they did a great job of keeping the house comfortable over summer with virtually no grid power. I expect I'll be using more power during winter but totally worth it for QoL.

    Another advantage of modern split systems is WiFi control and reporting of room temperatures so you can make the place a pleasure to return.

  • drilly on 10/05/2023 - 20:54

    We have split systems in all the rooms but have switched to an actual heater because it doesn't feel as dry. We went with Noirot and they're so good for the lil ones, and you don't wake up feeling like you've been sleeping in the desert.

  • Mrgreenz on 10/05/2023 - 20:56

    1. Only heating method, have gas spigots but was getting ac for the summer mainly anyway and split systems compare favourably $/heat output vs gas

    2. Never heard this being an issue, I imagine a split system pulls enough air through it that the radiant heat wouldn't make a huge difference.

    3. Yes there are tables that show this. But they are limited as every install will be different. Openings to adjacent areas, wall and ceiling construction and insulation, ceiling height, windows, orientation etc etc.

    I sized on lower size and am happy with the results. With solar it can make sense to just set timers to avoid having to crank the system to get it to a comfortable temp quickly.

  • kaleidoscope on 10/05/2023 - 23:23

    looking to cost us $300 this winter

    Bruh… That's like our MONTHLY additional energy cost (gas + elec) during winters. This goes for gas heater, personal heaters, oil heaters and extra hot water to make up the difference with solar hot water.

  • SomeRandom on 11/05/2023 - 00:44
    +1

    1) Yes, much cleaner/unstuffy feel compared with the gas heater.

    2) Ours gets a bit of morning sun, but has a good amount of open space around it which is also important.

    3) 16kW and 10 zones for a 4 bedroom house. Something important to consider is the number and location of air intakes. You need to make sure that internal doors are left open to avoid pressure issues. (i.e. if you have air intake from one area behind a closed (hallway) door it can be an issue).

    A solution is to get an extra air intake vent installed. It's pretty cheap to get done as part of the original install. This would allow you to close doors to seal off the back or front part of the house & reduce the overall volume of air to be heated/cooled.

    P.S.
    Oil Heaters for bedrooms overnight are a great idea.
    Thermostat set quite low, just enough to take the chill out of the air.

  • sovereign01 on 11/05/2023 - 01:53
    +2

    The best regular heater will create 1kw of heat from every 1kw of electricity.

    A reverse cycle (i.e heat pump) AC will create 3-5kw of heat from every 1kw of electricity.

    i.e They are significantly cheaper to run.

  • FittyFitty on 11/05/2023 - 02:13

    Just $300 for the winter? Bloody bargain.

  • jason101 on 11/05/2023 - 08:09
    +3

    If you’re approaching this from a quality of life perspective per your post, don’t forget about your quality of life in January when it’s 42’c, you’ll really be loving your new split system then as well.

  • cktftw on 11/05/2023 - 08:48

    I also refuse to use fossil fuels to directly heat my home.

    Unless you have solar and battery, where do you think the power for the airconditioning is coming from?

    • ESEMCE on 11/05/2023 - 08:54
      +3

      The point of this comment was RC versus combustion heater of some sort (wood or gas). It's not a CO2 argument.

      • cktftw on 11/05/2023 - 08:56
        -1

        then theres no need to make the comment about fossil fuel at all
        just making himself feel good thinking he's doing something for the environment

        • ESEMCE on 11/05/2023 - 10:18
          +2

          Dude it's solely about whether there is combustion products in the house, nothing more.
          So the direct fuel source is 100% relevant.
          Get off your own high horse!

    • drillvoice on 11/05/2023 - 09:07

      A growing amount of grid power is generated by renewable energy sources. But yes, the OP clearly says "directly", they are contrasting with direct combustion of eg fossil gas.

  • drillvoice on 11/05/2023 - 09:06

    RCAC is great - you can save a lot of money on heating in winter, plus gain cooling in Summer. Most modern options will have a 'fan only' option in summer which just blows air around, still great for cooling and uses less energy.

    In addition considering AC you should check that your place is properly insulated (ceiling most important) and do some draught-proofing. Gaps and cracks around doors or windows, or gaps in insulation, will severely compromise the effectiveness of any AC system.

    You should also check for state government rebates or incentives.

  • junet on 11/05/2023 - 09:51

    I had a Mitisubshi Electric 7.1kw installed late last year and started using it for heating instead of the gas ducted system. So far it uses around 1kw per 30mins when starting up and then around 0.5kw per 30mins after that. I have it set at 18 but after awhile it feels too warm so turn it down to 16. It's a different kind of heat than gas, like warm air and takes a bit longer to heat up. I also use an electric throw on the couch and it feels much nicer then warm air blowing.

    If i close all the doors its oversized for a 45sqm room but when open it flows to all the other rooms probably around 80+ sqm. There's a long vane function so it blows air further apparently. Half the cost was installation so there wasn't much point going to a lower spec system.

    I have the outdoor unit in the carport so it's undercover, i thought about installing it on the carport roof but it would get blasted with sun over summer and probably harder to maintan. It was a dream to run it over summer 35+ degree days, so cheaper winter heating vs gas ducted is just a bonus.

  • Boioioioi on 11/05/2023 - 09:52

    More efficient to use aircon too.

    A regular heater converts electricity to heat at roughly 1:1 efficiency.

    Air con in reverse cycle mode does not create heat. It gathers heat from outside and concentrates it into your house.

  • pnt on 11/05/2023 - 10:16

    Sizing - Mitsubishi Heavy Industries have a sizing chart: https://mhiaa.com.au/document/split-system-room-sizing-chart - it gets a little into detail, it depends on your building and it's insulation. I presume every manufacturer has a similar chart.

    P.S. Life expectancy is 10 years, if you want to consider that, but it's still worth it due to energy efficiency and utility. Our tradie installer said they are all don't last these days, price competition from china has made even the good brands flimsier.

    Bunnings can install, but even they said they are a bit too expensive when we purchased a unit from them. We used a qualified independent installer.

  • Worf on 11/05/2023 - 10:46

    Definitely use reverse cycle ac to heat house. It’s more efficient (heat pump… something about thermodynamics which I don’t quite understand), quicker to improve the perceived temperature in the room and quieter than a fan heater. Collectively, it makes sense from both cost and qol perspective.

    Our condenser unit gets the sun (north facing). I guess I could build a little shade screen around the unit. Not a deal breaker.

    Google ac calculator to determine the size of your unit. I have a couple of small 2kw for the bedrooms, plus a large (at least 7kw) for the open planned living room. 3 splits in total. Sometimes you can get multihead splits (one condenser unit and two heads) but the layout of our house wasn’t suitable.

    I have Mitsubishi electric units. I think msz-ap series, or the one before… they’ve been good.

  • Hangryuman on 11/05/2023 - 11:40

    on a QoL Quantity of Life question - I'd go LARGE - get the big one - split a/c to the max dude !

    but … before then check out your insulation and thermal mass situation and sun exposure

    a free-standing uninsulated house will lose heat in winter like nobody's home - ours cost at least $5 a day if not $10 per day to heat only part of it with 2 oil radiators going full blast

    and west-facing windows can turn those rooms into an oven in late afternoon summer

    now elsewhere we have ideal thermal mass in a first-floor unit with neighbours above, below and either side

    and good cross-ventilation with north-facing living for warm winter sun,

    and south-facing sleeping for cooler desired for sleep

    Our split air-con is used only on coldest or hottest days, and then only costs about $1 per day to run

    During the 4-year drought extreme heatwave around Jan 2020 we ran the air-con 24x7 and it cost about $2 a day to run

    so start with those questions

  • Oofy Doofy on 11/05/2023 - 12:03

    Heating the air is much more energy intensive than heating your body directly.

  • OzzyOzbourne on 11/05/2023 - 12:14

    Standard electric heaters are only ~100% efficient. Reverse cycle inverter aircon can be 300-500% efficient and can obviously heat and cool.
    I have solar and work from home a lot, so use the aircon as a heater in winter to supplement the ducted gas heating which helps spread the heat around the house

  • Unacceptable on 11/05/2023 - 15:41

    When I was poorer in late 2000 I had an oil fin heater (2-3kw, $50-100 purchased) in my room and ran whole day & night. Not knowing the efficiency I was bombed with electricity bill up to $400/month and I stopped using it. (Air gets so stuffy in the room)

    Now I’m still poor but have a ducted aircon installed 6 years ago (14-16kw $8,500) it’s so comfy and warm and consumes about 1-2kw/hour at 21c.

    • Venustrap87 on 11/05/2023 - 16:43

      How much is your bill now?

  • JustASmoothSkin on 11/05/2023 - 22:03

    Generally a split system will be about 3 times more efficient at warming a room then an equivalent btu room heater, also far less likely for someone to accidentally chuck a towel or piece of clothing over it causing a fire.

  • Spic3y on 12/05/2023 - 08:21
    +1

    I live in Tassie and have been using a reverse-cycle for years. We typically call them a heat pump down here because they aren't really needed to cool during the summer, but are used almost daily to heat in the winter.

    As far as installation questions, you are probably better off talking to an installer. In our house, the outdoor unit is on the roof but at our business it's on the ground. Both places have a 'higher power' unit than what is probably necessary for our use.

    Having said all that, we installed a wood heater at home last week and you really can't beat the heat output and aesthetic of a wood fire!

  • cybapete on 12/05/2023 - 09:37

    we use the airconditioner but our situation is unique the house is double brick with insulation in the walls so once you warm it up the heat lasts longer
    i find a quick 30 minute blast of the ac might last for an hour or more if it's not that cold it might go for 2-3 hours

  • jugsy on 03/07/2023 - 14:41

    We have ducted RC, and use the heater almost all winter. Barely makes a difference on the powerbill if you set it to a conservative temperature and be careful with doors/windows

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