Combi hot water or Kitchen instant hot water - on water meter.

phil_51

New kitchen being installed with a Dishwasher.

Have the feeling this is going to be extremely hard to work out but here you go.....

The pipe run from the combi bolier to the kitchen tap is 11 meters.

We are on a water meter.

Would it be cheaper running cost to have an electric hot water heater under the kitchen tap or stick with combi boiler. ?

Mark_Mark

11 metres is a long run, how long does it take for hot water to come through?

phil_51

Don't know will be in 1 new kitchen diner house extension. I think it will be about about 2 ltr just in the copper tube never mind heating time for combi boiler.

Mark_Mark

You may find 11 metres is too long and have to re site the boiler.

rob7475

Mark_Mark wrote: »

You may find 11 metres is too long and have to re site the boiler.

Really? We have a combi in the garage and the furthest tap is in the bathroom which is 2 levels up and must be 12m away. Takes about 15 seconds max to get hot water - even less if central heating is running.

StuC75

Sounds like will be a long payback period..

Gas per Kwh will be about 1/2 or 1/3rd of the cost of electricity to heat the water (also if heating on at the same time as using hot water then it may not be using much more with gas)..

So using electricity will heat quicker (so less water wasted getting to temperature - check flow rate to see how much this uses).. But for the time that water is running be costing more pennies per Kwh to heat the water -

so at what point does the energy used cost more than the water you have saved?

Are you currently on a water meter? can you quantify what your usage is, and how much water you could save my minimising the upto temperature flow?

Then look at how much hot water you might use from this as to what the higher KwH cost would be..

Net off the Cost and benefit (to see if its a net gain or cost) and divide the cost of the equipment to see what the payback period is - checking this with the devices likely lifespan & maintanence requirements...

rob7475

phil_51 wrote: »

New kitchen being installed with a Dishwasher.

Have the feeling this is going to be extremely hard to work out but here you go.....

The pipe run from the combi bolier to the kitchen tap is 11 meters.

We are on a water meter.

Would it be cheaper running cost to have an electric hot water heater under the kitchen tap or stick with combi boiler. ?

stick with the boiler. The cost of running a dedicated electric supply (will probably need this due to the high kw of the heater) and running the thing will be higher than sticking with the gas fired boiler.

StuC75

Also a Dishwasher will likely just have a cold water feed and heat what it needs - just like most modern washing machines... so its only really going to be what is used from the hot tap...

Mark_Mark

StuC75 wrote: »

Also a Dishwasher will likely just have a cold water feed and heat what it needs - just like most modern washing machines... so its only really going to be what is used from the hot tap...

I've never seen one with a hot feed.

Mark_Mark

rob7475 wrote: »

Really? We have a combi in the garage and the furthest tap is in the bathroom which is 2 levels up and must be 12m away. Takes about 15 seconds max to get hot water - even less if central heating is running.

I was advised against a run like that. But if you say so you must be correct.

Lgas

Have you considered one of these?
http://www.combisave.com/
I've never fit one and haven't seen them in action but they should save money on your water bill by reducing the flow of hot water to the tap until it has reached the desired temperature. They quote that you save 8 litres of water every time you turn a hot tap on.