combi heat pump option or not

JD6910

folks,

which is best in relation to geothermal:

combi heat pump option or separate tank system

all comments welcomed in terms of:

initial capital purchase costs - is there much of a difference?
ongoing running costs
does the combi provide enough water storage for a typical family home of 5 people.
all other comments

soundskin

The biggest difference i see with Combi vs separate tank is % hot water runtime for the heat pump on a hot water cycle. With combi units the heat pump will run usually from 15-25% on hot water (rest of the time doing heating). With stand alone tanks, i see as low as 10% run time for hot water.

Capital costs: separate tanks will cost more due to added pipe work, non return valves in some cases, separate location of tank to heat pump (HP on GF and tank on FF). Combi is a lot more straight forward install thus lower costs

Ongoing costs: Combi slightly more expensive due to lower volume, but hot water production isn't the major factor in heat pump running costs, heating the building is.

Combi enough water: Yes, i know plenty cases with 5 plus people with 160L tanks in their combi and they have plenty hot water. Mains/booster pressure, shower type, user shower time will play a big part in amount of hot water available. People are normally very happy with heat pump hot water production as the heat pump should be working on hot water priority.

I would never bother put in Solar with a good geo heat pump, hot water costs with a geo heat pump would be on average €150 per year, if you had solar and saved 70% per year, €105 saving. You would be 38 years paying off the solar if it cost 4k to install it.

JD6910

soundskin wrote: »

The biggest difference i see with Combi vs separate tank is % hot water runtime for the heat pump on a hot water cycle. With combi units the heat pump will run usually from 15-25% on hot water (rest of the time doing heating). With stand alone tanks, i see as low as 10% run time for hot water.

Capital costs: separate tanks will cost more due to added pipe work, non return valves in some cases, separate location of tank to heat pump (HP on GF and tank on FF). Combi is a lot more straight forward install thus lower costs

Ongoing costs: Combi slightly more expensive due to lower volume, but hot water production isn't the major factor in heat pump running costs, heating the building is.

Combi enough water: Yes, i know plenty cases with 5 plus people with 160L tanks in their combi and they have plenty hot water. Mains/booster pressure, shower type, user shower time will play a big part in amount of hot water available. People are normally very happy with heat pump hot water production as the heat pump should be working on hot water priority.

I would never bother put in Solar with a good geo heat pump, hot water costs with a geo heat pump would be on average €150 per year, if you had solar and saved 70% per year, €105 saving. You would be 38 years paying off the solar if it cost 4k to install it.

many thanks. great reply.

any idea how much more expensive the separate tank would be - approx figure would be useful.

soundskin

JD6910 wrote: »

many thanks. great reply.

any idea how much more expensive the separate tank would be - approx figure would be useful.

I reckon anywhere between 1.5 -2k would be the average between combi and sperate tank.