I generally like Daikin, but you should probably talk to a local vendor who's been in business in the area for a good number of years. They'll know what works in your area.

I've just been quoted a Mitsubishi AP60 in Dunedin. KW is dependent on the room so as above best to get an installer involved rather than guess work. 

For 8-9KW you'd be looking at the AP71 and AP80. For Mitsi, i think you have to go for the hypercore models if you want one that is going to work just as well at -5 (AP series isn't hypercore). 

We're talking to 3 prospective heat pump installers:

• One is saying we shouldn't go lower than a 6kwh unit (6.8kwh heating) - Mitsi
• The other two are saying we would be fine with a 5kwh unit (5.8-6kwh heating) - Daikin/Pana 

Going to the 6kwh unit increases cost but most importantly reduces the choices as to what we can install based on the physical size of the units - we can really only go for the designer slim units or a floor/recessed unit based on the way our lounge has been built.

Who's right here?

the first one is more likely to be right.

most calculations underestimate your requirements, causing you eternal (first world) pain IF you really want a warm room.

if you just don't want to be frozen and want it very mildly heated then you could get away with the latter.

how new is your house and what is the space of the area needing to be heated, how many windows and doors and open plans? also where in the country, how windy is your place, where is the inverter placed - is it sunny where it's placed, is it windy where it's placed, and distance of the pipe from inverter to indoor blower.

all these affect how much heat you need and how much heat loss and how efficient the system is

To already answer where you're going to go with this the house is not new and is single glazed, but the house is well insulated and holds its heat. We have a fireplace we'll continue to use and I think that's why the other suppliers have tried to work on a price point.

The first guys have said you may as well do it properly...

Our new ducted heat pump is probably oversized. Once the house is up to heat, even in the middle of winter, it is on maybe 25% of the time. We told them the house is pretty warm, well insulated, double glazed, etc, at night two 500w heaters is plenty, but they overprovisioned and the minimum output is 5kw. The problem with overprovisioning a ducted unit is sometimes you only want a little bit of heat, and the minimum is higher than you need, the heat has to go somewhere so one room heats up too much. My point is some installers do over-provision. This is particularly the case if you leave the unit on most of the time in winter, in that case you're just topping up and need relatively little power.

Do a test on a really cold day if you can find one this time of year: turn on two fan heaters in the room. If that keeps the area warm enough then 4kw is enough. If one fan heater does enough on a cool day that might be an ok test.

Generally a large unit running at 50% is said to be more efficient than a smaller unit running at 75%, even though smaller units have higher efficiencies. But they are larger, and more expensive.

Whatever you do, don't buy Panasonic. The ducted units are horrible, loud outdoor and indoor, generally unrefined and poorly thought through. Daikin is great (we have ducted and high wall), Mitsi is meant to be very good but I've never had one, Fujitsu was a bit loud indoor but worked very well and are reputable.

why is small higher COP heat pump less efficient than larger lower COP one?

^ if I could guess the larger the unit the more efficient it is at lower outputs but at high output it must less efficient than a small unit - obviously ignoring the space it's heating and whether or not it's actually heating it well.

Mrs AklBen has indicated that a small designer sized high-wall unit is the choice over a recessed floor unit, based on the measurements of something sub 900mm wide and going for a 6kWh model (better be safe than sorry) it only leaves us with the following:

• Daikin Zena Vogue 6kwh - 7.2kwh heating
• Mitsi Black Diamond (not the VCR) LN series 6kwh - 6.8 heating

Both are around the $4.5k mark, but the Daikin has a higher COP and is the better looking unit. We can go cheaper, around the $3.4k mark but the units are large and the wife is not happy with how they look.

My question still lingers around the Zena Vogue between their 5 and 6kwh models is a 6 and 7.2 kwh on heating respectively and the difference between the two models is $600. Would y'all still just go for the big one?

Batman:

 

why is small higher COP heat pump less efficient than larger lower COP one?

 

What I've heard in the past, but can't substantiate, is that an undersized heatpump working at 100% all the time uses more energy than a larger heat pump working at 50 - 75%.

timmmay:

 

Batman:

 

why is small higher COP heat pump less efficient than larger lower COP one?

 

 

What I've heard in the past, but can't substantiate, is that an undersized heatpump working at 100% all the time uses more energy than a larger heat pump working at 50 - 75%.

 

Kinda like a V8 on highway cruise vs. wringing out a small engine at high speed.