View Full Version : Daikin Altherma HT - hot water once or twice a day?

05-03-2012, 09:33 AM
Hi All,

I'm enjoying setting up our recently installed Daikin Altherma HT :)

I want to run this bad boy as low as possible to optimize efficiency. Naturallly!

Quick bit of advice would be great to get me going...

Is it most efficient to heat the hot water once a day at 55c or twice a day at 45c?

These are figures I have come to through trial and error based on our daily need for DHW.

Can anyone offer advice?

10-05-2012, 11:21 PM
Depends on what you use and how many Peeps.

There's 5 of us in our gaff so ours heats up 3 times a day!

08-10-2012, 09:22 PM
I would heat it once per day if you can get away with it.

10-10-2012, 01:20 PM
The cooler you keep the water the better the COP and cooler water loses less heat as well so you would be better running it at a lower temperature.

We've got an Alterma LT system and keep it on all the time - it doesn't seem to cost anymore than just having it on for a couple of hours a day and we get the benefit of heating the water during the day when the outside temperature is warmer rather than turning it on to heat the tank overnight when it's freezing cold outside and the tank is cooler as well so you've got a poor COP.

We are at home all day so the heating is running as well. But during the summer I can't see a significant difference in our power consumption between all day and timed sessions (we've got a power monitor on the Altherma supply)

17-10-2012, 05:15 PM
After much testing (and cold showers!) I'm come to this conclusion...

Due to the high standby consumption of the HT it actually doesn't save much elec trying to get away with heating the water only once a day, so best to heat the water twice a day to 60c. It seems best to just top up the hot water frequently rather than let it get completely cold and then have to blast it for a longer time in one burst.

Family of 4 on a mixer shower by the way.