Upgrade boiler in new house to Combi?

FreeBear

Steveotwo said:

@FreeBear
Ill look into it, Ive heard mixed things, don't they currently cost more to run? 

If poorly specified and badly set up, a heat pump can be very expensive to run, but so can a gas boiler. A well designed and tuned system has the potential to be cheaper to run. https://forums.moneysavingexpert.com/categories/heat-pumps is the place to ask questions. If you want to see what others are getting out of their heat pump, have a look at https://heatpumpmonitor.org/ - Some pretty impressive numbers there and some dismal ones too.

RavingMad

Given that you're already in the house, you must be seeing how much energy you're using to heat the tank? I only heat the water up to 45⁰ in the summer and it's about 4/5 kWh a day (30 mins in the morning) that does the 4 of us

Grenage

RavingMad said:

Given that you're already in the house, you must be seeing how much energy you're using to heat the tank? I only heat the water up to 45⁰ in the summer and it's about 4/5 kWh a day (30 mins in the morning) that does the 4 of us

Isn't that too low to kill bacteria?

FreeBear

Grenage said:

RavingMad said:

Given that you're already in the house, you must be seeing how much energy you're using to heat the tank? I only heat the water up to 45⁰ in the summer and it's about 4/5 kWh a day (30 mins in the morning) that does the 4 of us

Isn't that too low to kill bacteria?

Yes. But with an unvented DHW tank, the risk of getting bacteria in the tank is almost zero. With a vented tank, fed by a covered header tank, there is a slight risk. Open header tanks with birds or bats roosting above it would be a cause for concern, but an unlikely situation in most houses.

Albermarle

Grenage said:

RavingMad said:

Given that you're already in the house, you must be seeing how much energy you're using to heat the tank? I only heat the water up to 45⁰ in the summer and it's about 4/5 kWh a day (30 mins in the morning) that does the 4 of us

Isn't that too low to kill bacteria?

The recommended temperature is 60 to 65 degrees ( depending in what you read) to kill all Legionnaire bacteria.
However Legionnaires disease frequency in UK is very low, and in a domestic setting where there is water flow every day the chances are even lower. Also temperatures lower than 60 still kill the bacteria, but more slowly.
Plus hot water at 65 ( even if it drops to 60) will scald your hands.
Personally I think 45 is a bit low but the risk at 55 is minimal. 

Albermarle

Ectophile said:

I can't imagine the extra gas used by the existing boiler is going to cost £2000 over any reasonable time frame.

When I changed from non condensing to condensing and generally a more modern boiler, I saved about 15% in gas consumption. So about £100 then and about £150 now.

I'm nervous of the bills spiking from heating a water tank and not using all of the water that is heated

A lot depends on the hot water tank. If it is an old copper one, with some lagging around it, then it will be ineffecient and will cool down quite quickly.
If it is a new one with integrated insulation, any hot water you do not use will still be largely hot many hours later.

jonnydeppiwish!

FreeBear said:

Steveotwo said: Additionally I have gotten some qoutes for a combi upgrade with system flush and magnetic filter, been quoted around £2800 on some alpha tec and ideal logic max models. around 93% efficient.

Get a quote from someone like Octopus for a heat pump. Some posters here have been getting prices for roughly half the cost of a new gas boiler install. The quote I had earlier in the year was within a couple of hundred of what I paid for a new combi last year.

Properly specified and set up, the running costs should be comparable.

My quote from octopus was circa £7,500 for an ASHP. Was very tempted prior to that

FreeBear

Albermarle said:

Ectophile said:

I can't imagine the extra gas used by the existing boiler is going to cost £2000 over any reasonable time frame.

When I changed from non condensing to condensing and generally a more modern boiler, I saved about 15% in gas consumption. So about £100 then and about £150 now.

I'm nervous of the bills spiking from heating a water tank and not using all of the water that is heated

A lot depends on the hot water tank. If it is an old copper one, with some lagging around it, then it will be ineffecient and will cool down quite quickly.

With my old non-condensing Baxi back boiler, I had been using around 8000kWh per year. Several measures were put in place to cut gas consumption (turning gas off during the summer, using a programmable thermostat). This reduced consumption down to around 5000kWh/p.a.. Latest figures with the new combi suggests 3500kWh/p.a. or 30% saving. Cutting the gas bill by £75, I'm never going to recover the investment, but having a warm home and instant hot water offsets the cost somewhat. Also don't have to argue with a GS engineer when it comes to getting a Gas Safety certificate.

housebuyer143

I prefer a tank as you are not only future proofing but you also have a back up source should the boiler fail. We can run 2 showers at the same time with no issues as well which is good. As another poster says, it's about 50p a day to heat our 170ltr tank. We turn it on twice a day for 30 mins and we have amble hot water for 3 people. Depends on what tank you have though. 

Our 23 year old glowworm packed in this year and we had to replace it and it is probably 25-30% more efficient than the old one. I personally would say to keep the old one as long as you can because any savings will not touch the sides of a new boiler. 

Bare in mind that if you moved to a bigger house your gas bill will be much larger than your old one. Coming from a 2 bed to a 4 I really struggle with getting the house warm because it's just so big. We spend a lot more on heating unfortunately.

WhoisDannie

I used to have warm air heating and a hot water tank.

The hot water tank had a pilot light and with heating water for 2 having a shower every day we used approx 11 kWh a day for hot water.

When it was changed to a combi and radiators we still used 11 kWh a day for the same usage so since the pilot light used 3kWh a day I am actually using more gas to heat the hot water with a combi than to heat a hot water tank that was on 24 hrs a day, there was no timer.