I own a 2 bedroom villa, we have air con units in both the bedrooms ONLY. We are looking at upgrading these two wall mounted units and external compressors. I would like to reduce our electric bill as right now it is very high, and beleive these units are part to blame.

Could anyone out there recomend a power saving upgrade to our current air con system in the two bedrooms ? brand, approximate price including installation ?

ALSO,

We are looking at instaling a solar water heater, capacity approx 300Litres. Panels on roof and tank and pump at ground level, back up will need to be electric NOT gas. Again could anyone point me in the direction of price, fully fitted ?

I have sent out an email to a couple of the local companies on the Island and am yet to hear back form anyone.

Thanks Choppy

Not surprised you haven't heard back from anyone.

On the solar water heating front, when I was building I invited over a couple of different solar people over and told them, " just show me how this will save me money and I'll buy it". Neither company do show any savings and I ended up buying the big electric ones from Home Pro. This was all a few years ago mind you. Maybe solar has come down in price and now savings can be achieved.

Not surprised you haven't heard back from anyone.

On the solar water heating front, when I was building I invited over a couple of different solar people over and told them, " just show me how this will save me money and I'll buy it". Neither company do show any savings and I ended up buying the big electric ones from Home Pro. This was all a few years ago mind you. Maybe solar has come down in price and now savings can be achieved.

I have been working in Australia alot lately and everyone raves about the roof top water heaters, quoting savings of upto 60%. The way I see it in our house and am sure alot of others, the main drains on the power are the air con units, filter/pump on the pool, and the water heater. I just recently changed out the swimming pool system, still chlorine but much more efficient with less cycles required. The air con untis are the ones that came with the house and are running very inefficiently, as is our water boiler, so they are next on the change out/up grade list. Our latest electric bill was 6,200 baht and my partner tells me a 7-8% rise is on the cards.

Solar water heater at it's simplest form is black tube of water on the ceiling.

Abo Solar sells the solar water heaters. Pressurized are somewhere around 100kBath and unpressurized start from 10k, comes with 150-300 L tanks (made in China).

One of the Phuket TV members did buy similar product to his/hers hotel some time ago. Would be nice to know if these has been installed and what is the outcome.

I have been thinking of buying the Chinese models to my home.

6k per month with 2 ac and a pool..

not very high

I take it that your house is insulated, under the roof, + reflective foil? That you have an overhanging roof ensuring that your insulated wall isn't exposed to the sun? Don't buy an over sized AC unit, it will cool the room down and cut off before the moisture has also been extracted, it's the moisture that causes much of the discomfort. http://<URL Automatically Removed>/view.php?pg=thailand_air_conditioning

You could easily get 300 liters of water into coiled up black garden hose pipe on the roof. + some kind of expansion valve of course.

Cheap skate I know

There's a solar heater business just at the junction with Kajonkiet School - called "Mono -something-or-other".

Know nothing about it, other than owned and run by a guy from Scotland (who is often working offshore) and his Thai mrs.

As for aircons, know very little about them. I'm not been awkward, but just try and use them less - they circulate stale / bad air and germs, so I only use mine in the really hot season. Mine have now been off for about 3 weeks, and i doubt I'll use them again until next March.

Solar panels are expensive, but over the years have been coming down in price because of technological advances and volume. The Germans and Chinese are into the technology in a big way.

Solar hot water is common in Australia and suited to the climate. Families need large amounts of hot water for showers, etc. There are government subsidies paid in many places to install them. One down side, I was in Perth about 3 years ago when a massive hail storm, with fist sized chunks of ice, destroyed most of the rooftop solar panels in affected areas.

I wouldn't think solar water heating would be very cost effective in Thailand because the climate doesn't really require large amounts of heated water for home use. For the same reason the manufacturing volume wouldnt be there.

I have 3 AC units in the bedrooms (although we mainly use fans) and a pool. My monthly electic bill is around 1,800 baht.

Hi Choppy,

This is something that needs careful informed consideration. The following primer might help first before considering your options.

The key to lower operating cost of air conditioning is to lower cooling load requirement. If the ambient within the room is lower to begin with, the a/c works less hard to reach the desired temperature.

4 factors play a role on cooling load (heat that needs to be evicted). Room orientation, roof fabric, wall fabric, degree of wall shading.

Tackling these 4 factors helps to lower aircond operating costs. Although using energy efficient aircond may help operating costs albeit paying a premium. Solar air cond are available promising free energy during the day albeit a higher acquistion cost. Conversely, by not changing the equation by tacking some or all these 4 factors. the only solution is to upgrade to higher cooling capacity airconds and hence escalating operating cost.

Room orientation

An unshaded West or south west orientation have the highest insolation (sun radiation) rate. Supposing in Phuket the sun insolates an average of 5000W/m2/hr with an average of 12 hours of sunlight, the direct insolation of W and SW is about 8 hours but a quarter of that strength in the morning = 5000x8 + 5000x4x0.25 = 40,000 + 5000 = 45,000W/m2/hr or 45kW/m2/hr theoretical baking to be shrugged off in the night.

Roof fabric

Aluminium, steel has lower thermal mass than concrete or clay. The latter two re-radiates heat into the roof and eventually into through the ceiling far longer into the night than the former two. Inversely aluminium and steel have higher thermal admittance rate ie they readily radiate the heat abosrbed from the sun quicker than concrete or clay. Think of it as wasabe vs thai chilli. One burns but it's over quickly whereas the other burns all the way through for a long time.

Wall fabric

Autoclaved aerated concrete (AAC) has lower thermal mass than brick. Furthermore AAC has air pockets that disrupt heat conductivity making it an ideal insulator in Europe since it's first use in Sweden. Clay bricks are the thai chili of wall fabric. They don't burn as fast but they burn long and well into the night. This is good in the very cold places at night and very cool in the day with low humidity. Brick is a no no in the tropics and AAC is gaining traction in Asia. In Western Europe it's been the standard for over 50 years. It's gaining traction also in Australia, NZ, the UK and the US. An interesting material comes in the form of structured insulation panel (SIP) which could use a wood fascia with insulator sandwiched in between. Another variation of this form is insulated concrete forms (ICF). A polystyrene foam is sandwiched between concrete or AAC to provide a low thermal mass and low thermal gain fabric.

Degree of wall shading

More shade admits less thermal gain via insolation. Having a tree helps especially in the W and SW area.

Most of the heat is abosrbed through the walls and roof and a small part through the window. The heat is mostly in the infrared range. If you could block this portion out, your air-cond operating cost will come down because the ambient in the rooms will be lower than before.

If you feel as if the ceiling like a radiator heat down even through the night with the aircond at full blast, I assume most likely there's no insulation or the insulator's performance is of no effect through aging. That's radiant or radiation heat courtesy of the infrared spectrum. You can't see it of course but your body know it's there. One phenomenon that shows its presence is when you walk into a room at noon day sun without fan or a/c and all your sweat pores let loose a torrent of perspiration in an instant. If the roof is concrete or even glazed clay, they're are a good emitter. A gypsum ceiling board is no use. Lowering the ceiling height with a false ceiling makes matters worse if the net ceiling height is less than 8.5 feet because convective heat stacks up and build downwards towards the floor. A high ceiling of at least 10 feet minimises this heat stack effect.

So the correct approach is on deciding on low thermal mass fabric upon construction and then thermal gain as an add-on on the building fabric first before considering electro-mechanical means like fan or a/c. Proper insulation in combination with low thermal mass materials like AAC can reduce cooling load requirement with certain configuration using a lower HP a/c.

Cooked's suggestion on insulation deals with minimising thermal gain upon the building fabric. Short of tearing down and rebuilding with low thermal mass materials, it's the correct approach.

If it's not already there, this is the first low hanging fruit. Let's suppose you're renovating, then lowering thermal mass via construction materials used in combination with thermal gain insulators as Cooked suggested should help combat thermal gain overall.

For an existing building without extensive renovation on the walls, I suggest the following in ascending order of the lowest hanging fruit:-

A. Roof heat gain mitigation

A.1. Foil insulation within rooftop - Parsec Thermabrite III. The best as used by NASA

Must be installed over roof purlins to be effective otherwise might as well not do at all since installing it under will shorten the life of purlins through excess humidity and heat. If's steel it'll rust, if wood it'll rot...fast. Costs: foil material, labor for removing roof tiles, laying the foil over the purlins and re-laying the roof tiles. It's best to know your roof tile make and buy extra for there's bound to be a chance for tiles to crack if they've been there a long time.

A.2. Vent the roofspace - 16" turbine ventilator

Radiant heat gradually heats the air which forms a convective current within the roofspace. If you've worked before in a foil insulation covered roof without a ventilator, it can be very oppresive. Venting prevents convective heat buildup. Traditionally, venting into roof space entails installing admittance louvre on the ceiling to admit convective air current. However this negates cooling gain from a/c. So when used with A.1 and A.3, I recommend installing lourvre on the eaves (exterior celing space as part of the roof overhang. If deliberately installing louvre over interior ceiling space (where battens are not installed or modified to admit convection current, it should be of a shuttered type to minimise a/c cooling loss into the roof space if available.

A.3. Insulation on ceiling board with rockwool or glass wool ceiling battens

Rooftop insulation doesn't eliminate thermal gain. It just retards it ie thermal gain climb's slowly. The battens prevent it from re-radiating through the ceiling above your head downwards but also prevent it's escape from the build-up heat in the room. Conversely, because it retards re-radiating heat past the ceiling into the roof space, it will also keep the room cool longer and lower the air con cooling capacity requirement. ie 2HP to 1.5HP etc. If used with options A.1and A.2 the louvres located on under the eave since the battens will block the vents over the interior ceiling space unless the battens are custom-fitted to admit convection current.

I feel that it is necessary to have A.1 installed before A.3 if the material used is not sufficient treated against mold and mildew forming from rain infiltration.

A.4. Change to a lower thermal mass roof fabric like Aluminium or Stainless steel

This is expensive because it might also be estensive. Metal emit heat faster than masonry but also loses it just as fast - lower thermal mass (the capacity of heat stored or radiated by area). Metal roof decks need mitigation option A.1 and A.2 and optionally A.3 to be effective. So while it can be oppresive during the a sunny day, it cools dramatically quicker in the night since it doesn't store as much heat as concrete tiles. Examples of such is Colorbond from Bluescope steel.

B. Wall heat gain mitigation

B.1 Use heat reflecting paint

Nippon Paint - Solareflect and ICI Weather Max with Keep Cool ™ emulsions which reduces heat gain.

B.2. Shade with an aerobrise

This is a formwork which is equivalent to a fixed or movable vertical (N or S) or horizontal louvre (E or W) that shades the affected area. Best to add on after B.1 or B.4/B.3 and B.1

B.3 Encase wall with structured insulation panel (SIP)

A polystyrene or foam insulation with foil exterior sandwiched with a framed panelling of wood or equivalent framing material PVC or uPVC. This is decking a fascia panel over the walls. Building code restriction applies. With humidity prevalent, this may requires raised floor to bring up the high water mark, an anti-condensation layer to prevent condensation in between and a waterproofing layer prevent moisture infiltration.

B.1 or B.4 can be applied onto B.3

B.4. Coat with multi-purpose acrylo-ceramic coating

Anti-condensation, sound insulating and heat reflecting. This may or may not be the cheapest depending on the overall cost of implementing the others but having this helps tremendously short of rebuilding. Over here down south, Mascoat's Weatherbloc-IC insulation coating about MYR20 per sq ft (THB200 assuming MYR:THB conversion of 1:10). Mascoat products are used in oil and gas, maritime, manufacturing automobile industry where heat insulation, anti-condensation and sound insulation is a must. Alternatively could be applied on roof especially option A.4. Can be painted over so B.4 could be in place of B.3 with B.1 added on.

Increasing roof overhang would be an extensive re-roofing project so I exclude it but it can be considered. The whole aspect of roof overhang is to minimse direct insolation thermal gain. The other is to plant a tree to shade the affected area if suitable.

Depending on availability of materials, this may cost a bit more than 2 airconds but should decrease air cond cost as the room should stay cooler than before. The only service provider I managed to find for option A.1 and A.3 locally via google is triple w dot td dash building dot com slash services dot html. The rest except SIP should be available locally

I know it does not answer your question directly but hope it gives another perspective on cooling.

What Seaeagle mentioned is Mono-Sun Technology Co Ltd at taspower dot com. There's also ABO Trading and Amorn Group's household brand. The Phuket Gazzette on 7 Feb 2012 featured them.

Good luck!

halcyon

halcyon

nomen est omen

Halcyon, that is a bout as good a post as I've ever seen on the subject. I my case, and I imagine that of many others, is that the roof space isn't readily accessible so I would hesitate to put a fan up there. I will probably going for 'whirlygigs' which apparently are quite efficient.

Great post Halcyon, thanks.

Adding to that, maybe the cheapest and easiest way to lower the heating of the roof and building itself is to paint the roof with white color (or silver eg. creating an mirror). White paint has Titanium Oxide, which does the work. This way large amount of the solar radiation is reflected back to space and it will not heat the structure itself. -> Less heat mass -> Less radiation to from the roof to inside -> Less cooling.

This method is used for example in Geese http://www.everyculture.com/images/ctc_02_img0442.jpg

Then I think this is wrong.

Room orientation

An unshaded West or south west orientation have the highest insolation (sun radiation) rate. Supposing in Phuket the sun insolates an average of 5000W/m2/hr with an average of 12 hours of sunlight, the direct insolation of W and SW is about 8 hours but a quarter of that strength in the morning = 5000x8 + 5000x4x0.25 = 40,000 + 5000 = 45,000W/m2/hr or 45kW/m2/hr theoretical baking to be shrugged off in the night.

I understood that we receive maximum of 1200-1300W/m2 solar radiation here in Phuket. Yearly average would be something like 17MJ per day. This equals to 4700Wh/m2/day on average. That's still a great amount of radiation both to be cooled down and also if produced electricity with solar panels. Good panels are 20% efficient and therefore can produce 1kWh per m2 per day.

Solar water heaters are much more efficient as those simply collect the radiation and output it to the water as heat.

Then I think this is wrong.

Room orientation

An unshaded West or south west orientation have the highest insolation (sun radiation) rate. Supposing in Phuket the sun insolates an average of 5000W/m2/hr with an average of 12 hours of sunlight, the direct insolation of W and SW is about 8 hours but a quarter of that strength in the morning = 5000x8 + 5000x4x0.25 = 40,000 + 5000 = 45,000W/m2/hr or 45kW/m2/hr theoretical baking to be shrugged off in the night.

I understood that we receive maximum of 1200-1300W/m2 solar radiation here in Phuket. Yearly average would be something like 17MJ per day. This equals to 4700Wh/m2/day on average. That's still a great amount of radiation both to be cooled down and also if produced electricity with solar panels. Good panels are 20% efficient and therefore can produce 1kWh per m2 per day.

Thanks Olinki and you're right.

My bad, I misread the unit of measurement was supposed read kWh/m2/day.

I took it as kWh/m2 leaving out the per day part.

You can get these figures for Phuket here thanks to NASA's Langley Research Centre.

Look at the section which shows solar energy and surface meteorology.

http://www.gaisma.com/en/location/phuket.html

I live in Kuala Lumpur so the humidity here is horrid - high 80s sometimes 90s at noon well up to midnight.

That gaisma link was great. I have been trying to find that kind of information. Thanks.

There is an solar power meter on Krabi. Currently they have 605 W/m² solar radiation. Some good information as well.

http://www.aonangweather.com/

I have some ideas how to make very cheap solar hot water collector, but I fail the skill of building and would need somebody who have the skills and is interested of the subject. There is no need for expert building skills, basic should be enough. The idea is to make few prototypes, document it and probably just offer the plans as free to anyone who wishes to use it.

If anyone is interested being part of this, please PM me.

Halcyon, that is a bout as good a post as I've ever seen on the subject. I my case, and I imagine that of many others, is that the roof space isn't readily accessible so I would hesitate to put a fan up there. I will probably going for 'whirlygigs' which apparently are quite efficient.

Thanks Cooked. I suppose by that you mean the roof over there are sloped without much roof space between ceiling and roof?

I have two 14" whirlygigs on pitched roof. It deals with convective heat ok. There's a breeze current coming into the room if the window is opened. However, it won't stop the heat baking down through the ceiling board above. When it rains with strong wind, the rain infiltrates the roofspace and onto the ceilling board which then rots. I have replaced a few of the rotted plywood ones with that made of gypsum.

Solar water heater at it's simplest form is black tube of water on the ceiling.

Abo Solar sells the solar water heaters. Pressurized are somewhere around 100kBath and unpressurized start from 10k, comes with 150-300 L tanks (made in China).

One of the Phuket TV members did buy similar product to his/hers hotel some time ago. Would be nice to know if these has been installed and what is the outcome.

I have been thinking of buying the Chinese models to my home.

Oilinki,

Check out http://www.microsolarsystem.com -> Compare (on the left pane)

This to is by far the best design I have seen of a close-coupled (integrated storage tank) system.

And China copies this one like a plague but unless I am out of date many tend to fail after 3 years unless the it includes the crucial coaxial cold tube within the hot tube which they can't for patent violation reasons.

Solar water heater at it's simplest form is black tube of water on the ceiling.

Abo Solar sells the solar water heaters. Pressurized are somewhere around 100kBath and unpressurized start from 10k, comes with 150-300 L tanks (made in China).

One of the Phuket TV members did buy similar product to his/hers hotel some time ago. Would be nice to know if these has been installed and what is the outcome.

I have been thinking of buying the Chinese models to my home.

Oilinki,

Check out http://www.microsolarsystem.com -> Compare (on the left pane)

This to is by far the best design I have seen of a close-coupled (integrated storage tank) system.

And China copies this one like a plague but unless I am out of date many tend to fail after 3 years unless the it includes the crucial coaxial cold tube within the hot tube which they can't for patent violation reasons.

What is the coaxial cold tube with the hot tube and how does it protect the system?

I would think the physics of the solar heater is pretty basic. Absorb the radiation, transfer the heat to water and don't let the heat to be conducted out from the system. Passive systems cleverly use the expansion of heated water to create slow circulation of the system without any pumps.

There is some great projects done with the solar water heating. Panels and batch heaters.

http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm

Then again, it will come to engineering to make the system as efficient as possible and last longer.

Another thing to lower the electricity bill on air conditioned houses, is to decrease the power consumption to the minimum inside the house. Change old type incandescent light bulbs and halogen lights to lights with better efficiently. Replace plasma TV to LCD. Move anything that uses electricity or causes heating and is not required to be inside air conditioned rooms to out of the cooled rooms.

Simplified everything which uses electricity causes the same amount of heating.

If an aircon unit have an efficiency of 50%. Then one 100W light bulb heats up the space with 100W. To remove this excess heat the aircon needs work for 200W. Altogether the 100W bulb uses 300W of energy.

Not so seriously: We humans produce from 70 to hundreds of watts of heat depending of the activity. Just by looking at the energy consumption of the bedroom aircon, one could read who is having fun time

Halcyon, that is a bout as good a post as I've ever seen on the subject. I my case, and I imagine that of many others, is that the roof space isn't readily accessible so I would hesitate to put a fan up there. I will probably going for 'whirlygigs' which apparently are quite efficient.

Thanks Cooked. I suppose by that you mean the roof over there are sloped without much roof space between ceiling and roof?

I have two 14" whirlygigs on pitched roof. It deals with convective heat ok. There's a breeze current coming into the room if the window is opened. However, it won't stop the heat baking down through the ceiling board above. When it rains with strong wind, the rain infiltrates the roofspace and onto the ceilling board which then rots. I have replaced a few of the rotted plywood ones with that made of gypsum.

Access to the roof space in my case is difficult from beneath because there is a layer of insulation above the ceiling. This method of access is also unpleasant because it is HOT up there.

I can 'easily' remove the roof, but in the case of a fan stopping working in the rainy season I don't think so...

Solar water heater at it's simplest form is black tube of water on the ceiling.

Abo Solar sells the solar water heaters. Pressurized are somewhere around 100kBath and unpressurized start from 10k, comes with 150-300 L tanks (made in China).

One of the Phuket TV members did buy similar product to his/hers hotel some time ago. Would be nice to know if these has been installed and what is the outcome.

I have been thinking of buying the Chinese models to my home.

Oilinki,

Check out http://www.microsolarsystem.com -> Compare (on the left pane)

This to is by far the best design I have seen of a close-coupled (integrated storage tank) system.

And China copies this one like a plague but unless I am out of date many tend to fail after 3 years unless the it includes the crucial coaxial cold tube within the hot tube which they can't for patent violation reasons.

What is the coaxial cold tube with the hot tube and how does it protect the system?

I would think the physics of the solar heater is pretty basic. Absorb the radiation, transfer the heat to water and don't let the heat to be conducted out from the system. Passive systems cleverly use the expansion of heated water to create slow circulation of the system without any pumps.

There is some great projects done with the solar water heating. Panels and batch heaters.

http://www.builditso...ter_heating.htm

Then again, it will come to engineering to make the system as efficient as possible and last longer.

Coaxial means along the same axis - in this case the cold pipe is protected by the vacuum from the hot pipe of the evacuated borosilicate tube. So no mixing therefore no heat stagnation.

Heat stagnation is more prominent in a horizontal flow. It goes against the flow characteristics of hot fluids. Hence one of the first thing to look for in the performance of the solar water heater is to what extent are horizontal pipe present. That makes a difference between a 40-50 degree gain vs a 70-75 degree gain in water temperature. Single valve with horizontal flow prevents more water from being heated as much as it should when compared to multivalve without horizontal flow present.

Solar water heater at it's simplest form is black tube of water on the ceiling.

Abo Solar sells the solar water heaters. Pressurized are somewhere around 100kBath and unpressurized start from 10k, comes with 150-300 L tanks (made in China).

One of the Phuket TV members did buy similar product to his/hers hotel some time ago. Would be nice to know if these has been installed and what is the outcome.

I have been thinking of buying the Chinese models to my home.

Oilinki,

Check out http://www.microsolarsystem.com -> Compare (on the left pane)

This to is by far the best design I have seen of a close-coupled (integrated storage tank) system.

And China copies this one like a plague but unless I am out of date many tend to fail after 3 years unless the it includes the crucial coaxial cold tube within the hot tube which they can't for patent violation reasons.

What is the coaxial cold tube with the hot tube and how does it protect the system?

I would think the physics of the solar heater is pretty basic. Absorb the radiation, transfer the heat to water and don't let the heat to be conducted out from the system. Passive systems cleverly use the expansion of heated water to create slow circulation of the system without any pumps.

There is some great projects done with the solar water heating. Panels and batch heaters.

http://www.builditso...ter_heating.htm

Then again, it will come to engineering to make the system as efficient as possible and last longer.

Coaxial means along the same axis - in this case the cold pipe is protected by the vacuum from the hot pipe of the evacuated borosilicate tube. So no mixing therefore no heat stagnation.

Heat stagnation is more prominent in a horizontal flow. It goes against the flow characteristics of hot fluids. Hence one of the first thing to look for in the performance of the solar water heater is to what extent are horizontal pipe present. That makes a difference between a 40-50 degree gain vs a 70-75 degree gain in water temperature. Single valve with horizontal flow prevents more water from being heated as much as it should when compared to multivalve without horizontal flow present.

Thank Halcyon for your detailed replies, you have now left me with information overload will look into it a bit more deeply now. Would still be interested if anyone has any more info on shops that other than the one near Kajonkeiet (which I will re visit) who sell water heaters.

I sent out 7 emails to separate companies on the island with ref to the air con units and the water heater, and not a single one replied, they must be overrun at the 'mo to completely ignore me like that. Again if anyone knows a company that actually replies then a contact would be appreciated.

Oilinki: if I wasn't tied up with so many work projects I would definitely be interested in putting something together.

Thanks again choppy

In my opinion having done considerable research, Daikin are the best manufacturers of air conditioning units.

In the event you are going to use it every night, then I would choose an inverter model.

Regarding hot water, again in my opinion Panasonic make the best water heaters for a shower.

If you need hot water for washing the dishes, then install a water heater beneath the sink.

These are the cost effective methods, going down the solar road I would hate to think how many years it would take to break even.

In my opinion having done considerable research, Daikin are the best manufacturers of air conditioning units.

In the event you are going to use it every night, then I would choose an inverter model.

Agree, I have two Daikin Inverters and they are good on power consumption considering they run pretty much all day every day.

One of the Phuket TV members did buy similar product to his/hers hotel some time ago. Would be nice to know if these has been installed and what is the outcome.

That was me and I bought a lot of solar products, including ABO water heaters and garden lights.

I never got round to installing the solar water heaters, (because of time constraints), and they arr for sale at a discount price, never used. I have 5 150 litre units, (gravity fed) and they are currently stored near to Phuket Airport.

If anyone wants to buy them, please PM me. I'm not in Phuket now, but my hotel staff can deal with this if you're interested.

Simon

I have had a Solahart water heater installed up here in Chiang Mai

for the last 18 years, and its worked great,it was expensive at the

time as it was the only brand available at the time, made in Australia,

but i am sure it has paid for its self many times over,so it was a good

investment. and recommend that brand,the Chinese ones are far

cheaper and are not as efficient and i dont think they would be working

after 18 years.

Having hot water for the bath, all sinks and kitchen is great

regards Worgeordie

These are the cost effective methods, going down the solar road I would hate to think how many years it would take to break even.

This got me interested. Time for the math.

If we assume that daily hot water usage is 150 liters of 80 Celsius water. This is going to be mixed with ambient temperature (30 C) water for final mixed water usage. This equals to for example 300 liters of 55 C water.

It takes 1 calorie to heat 1 gram of water for 1 C. This is 1.163×10−6 kWh.

To heat the daily usage of 150 liters (150000 gram) of water for 50 degrees (80C - 30C) reguires thefore

150000g*50C Calories = 7500000 Calories. This is

7500000*1.163*10^-6 kWh = 8.7225kWh/day.

--------------------------

In Thailand the price per kWh (or unit if you wish) varies from 3.5 to 7 Baht/kWh.

Daily cost to heat the 150 liters of water is between 30.5Baht to 71Baht. Yearly cost is between 11,143Baht to 22,286Baht. (1-2kBaht/month).

In this case we assume that the extra piping and mixers cost about the same as the cost of the new electric water heaters would be.

If cheap Chinese hot water heater costs for example 10,000Baht, then the break even point is between 6 to 12 months.