ASHP hot water tank size

[wiffola]

Hi All,

I mentioned in another thread that we are very close to accepting a quote on a Daikin Altherma HT.

We have alot of difference in opinion (in each quote) on water tank size....Daikin 200l or 250l.

We have one bathroom on a thermostatic mixer shower, all appliances are cold feed, 2 adults and 2 children (girls).

The company will upgrade us to the 250l within the price already quoted. We have space for either size as it's just taller. It will be located in an airing cupboard on the first floor.

What are the pros and cons to going larger?

Weight? Heat up time? More energy needed? Better for defrost cycle?

[hyperion]

The main advantage would be the larger quantity of hot water that would be available to you, which could mean that the recovery time to reheat, say 100 litres would be less.
However, as you mention that all of your appliances are cold feed, you could probably manage with the 200litre tank. As you have been offered the 250 as a no cost option, you are spoilt for choice.
The HT does not have a booster heater as the Altherma provides all of the useable heat via recovery, therefore this is all at maximum energy efficiency.
If you have the "white meter" or the old Economy 7 electrical supply, you can take advantage of this and programme the HT to regenerate your hot water during "off peak" thereby creating a tank full of hot water ready for the next day at a slightly lower energy tariff.

[wiffola]

Thanks for the response.

So would you confirm that 260l is the best option if it's at no extra charge?

[hyperion]

If physical space is not an issue, then the 250L for the price of the 200L would probably be best option.