Cooling the home, are these costs real?

[ericmark]

From the BBC and I consider what my fans and AC cost. The fans are around 70 watt, they tend to run for an extended time, as clearly they don't cool the room, just the evaporation of sweat cools one's body, so typically run for 10 hours a day, on cooler days, on their own, at 30p/kWh so around 21p per day, but when the AC is required the fans often used as well.
At 700 watt, if used for same time, easy £2.10 per day, but tend to be used for less time, so under £2 per day, but as said likely fans used as well.
I don't have a built-in air-con, but would have thought they were more, not less, efficient to the portable type.

If it is hot, then the AC goes on, but if it is hot, there is loads of solar power, we lose the money paid for export, but that is 15p/kWh so half the cost of air con for someone without solar panels.

So the AC may cost us £1 per day, so where does £43.40 come from? I look back to when I moved to Octopus, in May, and the first 6 weeks we used around £5 of electric, since then we have produced more than we used money wise, and this includes the standing charge.

What is the point of having solar panels and then being too hot? The more sun there is, the more power there is to run the AC. It is more down to the prices charged for an AC unit, a few years ago I paid under £200 can't remember actual cost, but now 3 to 4 times the price, talk about rip of Britten.

 

[Rodders53]

The "portable aircon" has to run at 1kW (approx 26p/kWh) but 24 hours for the full 7 days to get to £43.40

Stupid, stupid ignorant lazy Journalism by an illiterate. OR Arificial Ignorance.

NB Those numbers are, BBC states, from USwitch data... so not sure who is the more stupid as neither have 'sanity checked' the numbers, and that took me all of 60 seconds (if that).

 

[morqthana]

where does £43.40 come from?

7 x 24 x £0.25833

 

[Old Salt]

My built in air con costs about £1 per day. Not scientific just watching in home display. Not on all day either probably somewhere between 6-8 hours when it was really hot. 2 units, one in the lounge and one in the bedroom, with doors open to let it circulate around a 2 bed bungalow.

 

[Harry Bloomfield]

At 700 watt, if used for same time, easy £2.10 per day, but tend to be used for less time, so under £2 per day, but as said likely fans used as well.
I don't have a built-in air-con, but would have thought they were more, not less, efficient to the portable type.

I would expect, that the 'built-in', means a large part of the house is covered, whereas the portable will only be cooling the one room, or even one of those nasty evaporation air coolers. We make good use of fans, for those exceptional days, but generally - my regime of opening windows for overnight cooling, and drawing blinds during the day, obviates the need for fans. In the bedroom we have a ceiling fan, only needed when there is hot, still night air. That goes on for the entire night. Then a floor fan in the living room, for use as needed, and a second one in the kitchen.

 

[JohnW2]

In addition to everything else, the BBC seem to have been a little silly to include 'desktop fan' in their table since, although it might help people to feel cooler, it would not 'cool the room'. In fact, if one wanted to be pedantic, it would probably slightly increase the temp of the room!

 

[ericmark]

Much depends on the house, I never found the old house got too hot, and this house living room does get too hot, but the dinning room stays reasonable cool, so the cheap method would be to use the dinning room as the living room in summer.

But we should compare like with like.

I did look at the idea of cooling the room with fans. This has to be overnight, and the main problem was to get cold air into the house, without insects or bats or other intruders. So a blind would stop bats, and lack of light for insects. But cats and humans are not so easy, so have to use upper windows only, and it did not seem to be practicable to automate fan cooling. The only real way was to manually come down and open patio doors, so once the room temperature exceeded around 26ºC, the fan option had gone.

So the portable AC was not really big enough for the room, so the method was not to let the room heat up, so really wanted it on at 25ºC to keep the room cool, however there are two problems, one is the condensate which needs emptying, and second is how to get rid of the heat without leaving a window open.

A gallon bottle will take around 2 to 4 hours to fill, and the easy way to get rid of the hot air is up the chimney, it is designed to get rid of hot gas after all.

With an installed AC, be it in the window or a split unit, the getting rid of condensate and removing the heat without leaving the window open is not a problem, so it could be left on for longer. When going out, I had to switch my portable one off, but could switch it on before arriving home.

However, the portable unit will draw in air from the rest of the house, which must be replaced from outside, where the built-in type does not, so built in types should be better not worse, the main waste of energy with my portable is that the fan runs even when the heat pump switches off on the thermostat.

But the main point, is it was only likely used for around 20 days in the year, and only for around 8 hours in the day, so the cost to install a fixed heat pump is not worth it for the amount of time it is used for.

 

[Harry Bloomfield]

This has to be overnight, and the main problem was to get cold air into the house, without insects or bats or other intruders. So a blind would stop bats, and lack of light for insects. But cats and humans are not so easy, so have to use upper windows only, and it did not seem to be practicable to automate fan cooling.

Heat in the house, given a chance, naturally rises to the upper floors. As said, when it's too warm in the house, we open the upper floor windows, front and rear, that provides a good flow of the cooler night air, through the house. Failing the 'good flow', I place an 18" desk fan, in front of an open window, to provide the flow. I hate having flies and moths in the house, so we only open them after lights off. We also have regular bats in the garden, but never do we get bats, or insects in the house.

During the day, we close blinds, on the sunny side, to reduce internal heat gain, and have the side door open, guarded by a fly screen. My regime, means that even in a long hot period, it takes several days for the house to start to overheat.

 

[jj4091]

I would expect, that the 'built-in', means a large part of the house is covered, whereas the portable will only be cooling the one room, or even one of those nasty evaporation air coolers. We make good use of fans, for those exceptional days, but generally - my regime of opening windows for overnight cooling, and drawing blinds during the day, obviates the need for fans. In the bedroom we have a ceiling fan, only needed when there is hot, still night air. That goes on for the entire night. Then a floor fan in the living room, for use as needed, and a second one in the kitchen.

Hi Harry can I ask where in the North you live that it has been hot enough to need fans or aircon.
In S.W. Cumbria we haven't had weather that would need either, even though it's been the best summer we have had for years.
Perhaps I need to relocate.

 

[FrodoOne]

While I only "scanned' the BBC article
a cost of over £100 be week for "Air Conditioning" a "Living Room" is quite ridiculous
and
you may note that I am in Australia, where Cooling in Summer is essential.

Further, modern "Reverse Cycle" "Inverter" Air Conditioners are actually efficient "Heat Pumps".

They can cool one or more rooms in Summer
and
heat those same rooms in Winter,
at less cost than the cost of Winter Fuel, be it Gas, Electricity, Oil etc.
or the inconvenience of Wood.

Because of the "Inverter" principle, they do not "draw" their maximum rated capacity after the desired temperature has been reached.
Their input of electricity and the transfer of heat is reduced to just maintain the required temperature.

The efficiency of a "Heat Pump" can be 300% to 400%.
This means that - at 300% - for heating, you get 3 kWh (10800 kJ) of heat out for every 1 kWh that you supply.
The same applies for heat transfer in the opposite direction, when cooling.

While I am aware of the cost and utility of using "Reverse Cycle" Air Conditioning,
because I live in Melbourne, where the Summers are usually not Humid,
I elected to install "Evaporative Cooling" - instead of Air Conditioning - as many do in this city.
The "Unit" concerned uses water evaporated on "grids" by a current of air to cool that air by the evaporation of water.
(540 Calories per Gram of water - if you remember your High School Physics relating to the Latent Heat of Evaporation -
or 2260 kJ per kg of water
and
water is almost free.)
This is even cheaper than Reverse Cycle Air Conditioning, using only a fan to run it,
but
the disadvantage is an increase in Humidity.
On days of 40 Celsius, and over, the temperature inside my house has not exceeded 28 Celsius, which is quite comfortable when one is wearing light Summer clothing.
However, the inside humidity may then be 75% with the outside humidity only 20% !)

The Australian State of Victoria is "phasing out" the use of (Natural) Gas to transition to
"All Electric Living".

Victoria’s Gas Substitution Roadmap

Learn about Victoria's gas substitution roadmap and how its guiding our state towards zero emissions.

www.planning.vic.gov.au

 

[morqthana]

A month or so ago I was thinking of relocating to Lerwick.

 

[ericmark]

I remember the water bottles covered in wet sack cloth hanging off the wing mirrors of wagons. It worked well. I have seen containers with some edging to keep water in place, and loads of rags on the roof. With a second roof above to stop direct sun.

But our homes don't have flat roofs, and there is a limit as to what can be done as a retro fit.

I saw the problems with DHW solar panels. Getting hot water into the house without, so many loses, not to make it pointless, is a problem, and I would think a PV solar panel driving a heat pump will likely work better, as it can do other things when not running the heat pump.

So with batteries, off-peak, export rates etc. Hard to cost running a heat pump. But £43.40 to run a single portable AC unit seems daft, it does vary, think my portable AC draws 750 watt, but some can draw 1538 watt, a random one found on the internet and cools it claims at 4100 watt, and if one needs a window part open to stick the pipe out, then, there must be loses, due to warm air also getting in.

So a fixed AC should always be better to a portable one. This type

stuck on a box in the window, must do better to this type

all very well showing this

but how many people have the old slash windows? This

is more normal, and the major problem is leaving the window open. Hence, why I made an adaptor to blow it up the chimney, but I digress, the point is it does not start to run until 11 am, and will be turned off at 8 pm except on very odd times. So 9 x 1538 = 14 kWh approx x 7 = 97 kWh at 25p/kWh that's £25 per week, basic half what the BBC is claiming. There must be some homes with picture windows,

where it does need that much cooling, but most people have homes more like this

there are bay windows

which can capture more heat, so there is no one fits all. My house

with the solar panels, the living room facing top right, is not on the ground floor, so the trees do not stop the sun. But many homes, trees can shield the sun.

 

[martygturner]

just lazy jurno : uswitch actually state :

Device	Av. minutes used per week	Cost per hour/cycle	Cost per week per household	Cost per year per household
Amp	171.5	£0.04	£0.11	£5.74
Built-in air con system	204	£0.70	£2.36	£122.82

Bit of a difference... still it is the beeb

 

[Harry Bloomfield]

I remember the water bottles covered in wet sack cloth hanging off the wing mirrors of wagons. It worked well. I have seen containers with some edging to keep water in place, and loads of rags on the roof. With a second roof above to stop direct sun.

I remember a water-sack, deliberately designed to leak the water inside, to keep the outside wet, allowing evaporation to cool the contents.

 

[plugwash]

Typical "portable ACs" with a single flexible hose are inefficient for serveral reasons.

1. The refrigeration machinery (which makes heat) is inside the room.
2. They use room air to cool the "hot side", which is then exhausted. This room air must be replaced by outside air leaking into the room.
3. The hose used to exhaust the hot air is generally uninsulated, so much of the heat gets back into the room.

Window units are more efficient and are popular in some countries, but as eric says there are issues with compatibility with our windows.

Unfortunately, my understanding is that refridgerant handling laws in the UK rule out self-installation of split systems using flourocarbon refriderants. In theory a CO2 system would avoid this but CO2 systems have other problems.