I have just built a house for my son in Chomtong and I am looking to install an electric water heater ( instant shower type ) can anyone recommend a good brand and where to buy in Chiang Mai.

my Thai neigbour and mate who is the local guru in matters such as this (OIC Maintenance, Saha Farm in Lop Buri) recommends 'Panasonic' for water heaters.

go for the named brands, and go for a higher kw, which gives you hotter water during the cold evenings and mornings, i just had fitted a heater that we bought top floor robinsons, 3.5k b , fitted the next day, 500b. strangely enough never heard of the make i bought avivanna, from the usa.pretty good though

For Chomthong district you will need high power in teh winter months. Don't even consider anything lower than 6000 Watt. If it's at all in the mountains then electric may not even cut it and you would go for gas. Where you buy doesn't matter much, all electrical goods stores have a good selection.

(Though a 10,000 Watt one may be harder to find).

Also, keep in mind this is pretty high power, so it will need to be on its own breaker cirtcuit, and the cabling needs to support the load.

Don't even consider anything lower than 6000 Watt. If it's at all in the mountains then electric may not even cut it and you would go for gas. Where you buy doesn't matter much, all electrical goods stores have a good selection.

(Though a 10,000 Watt one may be harder to find).

Also, keep in mind this is pretty high power, so it will need to be on its own breaker cirtcuit, and the cabling needs to support the load.

I concur that the issue is probably going to be the power supply. I believe that the standard in villages is still only 5 Amps, although you can request and hopefully get 15. Keep in mind, though, that even 15 amps won't get you far in terms of load [Amps * Volts = Watts; 15 A x 240 V = 3,600 Watts]. If you can get triphase (3 x 15 Amps) there are three-phase water heaters available from Stiebel, Siemens, and others capable of providing hot water even in winter months, but they are expensive to purchase and tricky to set up.

Besides the gas-powered solution you mentioned, with its inherent safety risks, my advice would be a boiler. They are usually rated at 2 Kw or less, which won't stress the system too much, and will always provide water at the desidred temperature without the annoying fluctuations typical of on-demand heaters.