Air-con running costs - have I got it right?

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Air-con running costs - have I got it right?

Postby fyfin » Sat Jul 29, 2017 4:07 pm

Some of my friends will swelter in this heat because they won't use their aircon units due to the huge cost of electricity. Some are recent install with inverters and I was going to explain that it's not as costly as they think but I want to get my facts right first.

Looking at my own split system unit in one room it shows cooling capacity 2.7kW Power input 870w and SEER (whatever that is) of 5.6, then Heating capacity 2.8kW, power input 900w and SCOP(3.8)

Would I be right in saying that if I use it for cooling and it's working flat out it would only be consuming 870w and if my unit cost is 14.4 cents per kWh then my cost would be 0.870 x 14.4c = 12.5 cents per hour. I'm sure the engineer mentioned that it would be lower for some reason or other but maybe I misunderstood, however, I'm happy to pay 12.5 cents and hour to keep cool assuming my calculations are correct.

Awaiting the expert replies.
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Re: Air-con running costs - have I got it right?

Postby TorreDelAguila » Sat Jul 29, 2017 4:33 pm

Your calculation is correct. These units (heating or cooling) have two sets of figures.

For example, for heating, a figure of 2.5kW may be stated, which means the unit is able to produce the heat output equivalent of a 2.5kW fan heater. However, these AC units are HEAT PUMPS, which use their power to transfer heat from outside to inside (in the case of room heating), or vice-versa (when cooling a room). As such, they use energy more efficiently, and so - in order to kick out "2.5kW of heat" they might only consume 850W of electrical energy.

Inverters... Non-inverter types of AC usually run the large fans in their outside units either on or off. When they start up (cycle on) there is usually a large current demand. Inverter types feature a 'soft start' (= gentle start) for the motor, and the power the motor consumes is carefully regulated accordimg to need by an electronic "inverter" (DC to AC) circuit. This all leads to lowered electricity consumption.

AC units are "heat pumps"' and a more energy-efficient way of producing heat than simply connecting a bit of resistance wire to the mains - which is what radiant, fan and immersion heaters do. Also, what those so-called infra-red panels do in practice; don't be fooled by them.
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Re: Air-con running costs - have I got it right?

Postby costakid » Sat Jul 29, 2017 4:40 pm

We use ours in the lounge during July and August for about 3 hours every afternoon. I don’t notice any difference in the electric bill.

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Re: Air-con running costs - have I got it right?

Postby fyfin » Sat Jul 29, 2017 4:46 pm

Thank you for great explanation Torre - I can now pass on the info knowing I got it right. I just find it odd that some of our friends won't use it and yet in UK they probably used central heating for 4 months of the year. Seems some sort of perverse logic that they shouldn't pay for cooling!
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Re: Air-con running costs - have I got it right?

Postby peteroldracer » Sat Jul 29, 2017 5:13 pm

You should try the humid heat that seems the norm up here in Murcia - whatever it costs it is essential! We have replaced the old aircon units that were put in when the house was built in 2001 with LG inverters, and run the bedroom one cooling to 26 degrees. One night's operation fills a 5 litre bottle....
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Re: Air-con running costs - have I got it right?

Postby fyfin » Sat Jul 29, 2017 6:15 pm

26 deg is what we set it too as well during the night. Makes such a difference .
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Re: Air-con running costs - have I got it right?

Postby Wicksey » Sun Jul 30, 2017 10:24 am

I've only had experience of aircon that have a huge fan units outside on the wall. Are converter aircon units different? If it only takes 850w to use then it sounds very efficient.

We don't have the outside wall space to have a unit directly connected to the outside so not sure how we would arrange it if we did want one. Our living room will not go below 30 degrees at the moment even with fans on all day and it's getting a bit suffocating! We have thought about a mobile unit but then the ones we have looked at have a pipe going out through the window like a tumbledryer, so that rather defeats the object if we have to have the window open.

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Re: Air-con running costs - have I got it right?

Postby peteroldracer » Sun Jul 30, 2017 11:24 am

Wicksey, they are 'inverter', not 'converter' and the exterior unit can be up to around 6 metres away from the connection through the wall to the interior unit, if that helps? Talk to an expert installer, as there are a few factors cowboys will not know or care about, like there needs to be a minimum of three metres of copper pipe connecting the two, even if this means having a neat coil behind the exterior unit, and that you should allow for the very high heat output outside - the hot air extracted has to go somewhere, and a neighbour might not want your 50 degrees adding to his space!
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Re: Air-con running costs - have I got it right?

Postby Wicksey » Sun Jul 30, 2017 12:20 pm

Thank you Peter for that info. We don't have any neighbours so that's not a problem, but it's placing an outside unit that I was hoping to avoid. We have quite large windows and so outside space on the walls is limited plus all the front of the house has a conservatory on it, so being able to put a unit indoors on an interior wall and feed it all outside is a bit tricky.

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Re: Air-con running costs - have I got it right?

Postby El Cid » Sun Jul 30, 2017 12:25 pm

I have seen the compressor unit fitted at ground level on a terrace. Also, they can be installed in the open. One of ours is on a flat roof fully exposed to the elements. The pipes can be longer than 6m. It depends on the length of the supplied pipe. 10m is also common but they can be extended.

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Re: Air-con running costs - have I got it right?

Postby Lyric » Sun Jul 30, 2017 2:58 pm

Both mine are sat on the terracing around the house at ground level, the internal units both being in the upstairs living accommodation, house being upside down.

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Re: Air-con running costs - have I got it right?

Postby fyfin » Sun Jul 30, 2017 5:25 pm

really worth doing and shouldn't be too expensive. We paid €599 euros to have a split system installed and it works absolutely brilliantly. As previous posting the running cost is minimal and as I said if you can afford it, do it!
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Re: Air-con running costs - have I got it right?

Postby peteroldracer » Sun Jul 30, 2017 6:43 pm

As with any major purchase, do the research - into the installers, the manufacturers and if you can the client feedback. We found a recommended firm, they pushed for a particular make and when we looked them up they had a string of bad comments. We bought Panasonic in Comares, and LG here - so far we are content.
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Re: Air-con running costs - have I got it ?

Postby TorreDelAguila » Mon Jul 31, 2017 1:57 pm

For most reputable makes of 'split' AC, it's possible to have the two units separated by up to 15m of piping, SFAIK.

Beware those €150-200 portable units, with the single exhaust hose that needs to go out through a window. The design of all these is seriously flawed.

Although chilled air is blown out into the room, and hot air exhausted to outside, the air that eventually gets thrown outside comes . . . . wait for it . . . . from inside the room!

So, the newly cooled air in your room is actually being sucked away and sent outside. It has to be replaced (obviously) - and where does this come from? Another warm room, or, worse, from outside! Hell's bells!!!

There is a way to make one of these units much more efficient, and that is to fit a second (intake) hose to the back of the unit, where it takes in room air*, and run this second hose to outside (or somewhere else). That way, the room air is just chilled by the unit, and not forced to take in hot air from outside.

* Fit a second hose, and blank off surplus air intake slits (gaffer tape works well enough).

The improvement in room cooling is really noticeable, and cheaper to run.
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Re: Air-con running costs - have I got it right?

Postby Wicksey » Thu Aug 24, 2017 12:30 pm

I am resurrecting this thread as, after a month of feeling quite ill with the heat, we are both looking at aircon units now, but still the question of where it would go is still a big problem.

We have a small house with very little available space on the interior walls to put one on and I am still wondering if one in our bedroom would be overkill as it's so small (3x4m x2.7m high plus one wall is taken up by a huge wardrobe so the space is actually smaller than that). I know we could put the outside unit on the ground which is possible but my OH is so sensitive to noise that we also wonder if the rumble of the outside unit would be too much for him. Where we lived before there were units on the flat roof but we could hear them rumbling all the time they were on.

I have seen this one https://www.carrefour.es/aire-acondicio ... -2205097/p
which is attractive as it has a very low db rating for the inside unit but there's still the question as to the pipework/wires that run between the interior and exterior units. I'm not sure how we would get power to it. It seems that the previous owners have already taken extensions off existing sockets into an extension they built and for sockets plugs so I'm not sure how we'd power it .

As our house is so small I am almost thinking about having a unit centrally in the hallway which would be easier to install and letting it waft around the 3 rooms that we want cooled, ie bedroom livingroom and kitchen/dining hallway which would be better than nothing. We have a pitched roof and the rear of the house is almost up against the rockface and the front has a conservatory on it. One side wall has a sunscreen attached to it in the summer, and the other side has various storage units for wood etc, so we have little choice as to where we could place an outside unit.

Are mobile aircon units really that inefficient as Torredeaguila stated? It would be a lot easier even if we just used it to cool the temperature in the bedroom before we went to bed!

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Re: Air-con running costs - have I got it right?

Postby fyfin » Thu Aug 24, 2017 1:28 pm

We already had pre-installed system supplying 3 rooms and that has a central system in the bathroom ceiling space. We recently put one in the bedroom and it's very quiet and makes a huge difference. Well worth it.
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Re: Air-con running costs - have I got it right?

Postby TorreDelAguila » Fri Aug 25, 2017 7:41 am

Hi Wicksey,

I think that putting an AC unit in a separated hallway is not a good idea, because the airflow around the main rooms you want to cool will be limited.

Outside units can be installed a short distance away from the building (a protected pipe and cable run joins to the house) if need be, and outside wall fixing is not convenient.

That LG unit looks ok. There are also "2+1" units available from some manufacturers that consist of one outside unit, coupled with one standard and one smaller (eg bedroom) inside units. Allows two rooms to be operated from one outside device; price can be attractive.

Portable devices have the efficiency problem I described, but this can be overcome by DIY modifying/fitting a second (inlet) hose. Guarantee to pot, obviously. Also, none of these mobile units are quiet, it seems. I wouldn't want to try to sleep near one running. They sound quiet enough in a big superstore, but not in a domestic setting!

Might be worth getting an AC fitter in (via your chosen store or supplier) to look round and advise. They are experts at this, and might come up with an idea or two you haven't thought of.
Last edited by TorreDelAguila on Fri Aug 25, 2017 8:04 am, edited 1 time in total.
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Re: Air-con running costs - have I got it right?

Postby Lyric » Fri Aug 25, 2017 7:47 am

I was going to say what TDA has, seek professional advice or two, don't think Hall is a good idea, the air won't circulate like you think. My floor mounted inverters are mounted about six inches away from the wall. Send MrW up to see if he could cope with the noise.

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Re: Air-con running costs - have I got it right?

Postby BENIDORM » Fri Aug 25, 2017 9:48 am

Wicksey,
Some good advice there from the 'crew'.
I've tried portable air con and dehumidifier units, OK but not as efficient as a 'proper' unit, and I would agree that you would be better to bring in a professional to advise and fit a permanent unit.

This year we've used our air-con more than ever before, and without it I think it really would have been very uncomfortable, we leave one unit on low most of the day and we expect the electric bill to be higher and I may have to sell my gold teeth to pay it...but I don't care .. :D

We visited a Spanish family the other day, they don't have air-con and when we arrived the doors where open and a weak voice told us to come in..
They have a big lounge and when we entered into it all we could see was spreadeagled bra-less scantily clad bodies everywhere and being a Gentleman I quickly averted my eyes and talked to the wall.. :oops:
The scene resembled the aftermath of a hot and steamy orgy , ( please note that I don't have any experience of such a spectacle, but I do have a good imagination.)
Most of the men folk where wisely down at the nearest bar supporting the local economy.

I had an instant flash-back to when I was about nine and a quarter years of age and I was visiting my 'Lady of the Manor' Aunt, I was perched on the edge of a chaise-lounge with my shirt buttoned incorrectly and I was wearing odd socks, red and green --port and starboard, and I suddenly blurted out that I was ' Sweating like a pig'.
My Aunt Nellie rolled her eyes furiously like a one-armed bandit and I waited to see if she hit the jackpot, but she suddenly stated in a loud voice....Horses Sweat, Men Perspire and Ladies Glow...and don't forget that young man ..!

We quickly left our unfortunate friends home and returned to the luxury of our air-con cooled home, and we sat sipping iced lemon tea and watched a film about polar bears and penguins.....
So I really would recommend investing in air-con units and maybe some ear-plugs for Mr .W.... :lol:
Regards,
Gordon.. :wave:

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Re: Air-con running costs - have I got it right?

Postby TorreDelAguila » Fri Aug 25, 2017 10:51 am

Oh dear. I was just getting interested in what the Lady of the Manor was going to do next, with the incorrectly unbuttoned young man . . . . . and then I had to wake up!
Could have been a "formative moment" for you; it's what aunts are for, after all. :roll:
Chris


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