Cost of hot water

recovering_spendaholic

Sorry if I seem to be a bit dim (I am!) but does anyone know if it is expensive to run the hot water only programme on the central heating? I have a normal (not combi) 2 year old boiler and I always have it set for the hot water to be on for 2 hours of a morning and 5 hours of an evening - it's just what I have always done. My friend says that this is really wasteful and will be costing me money - I haven't had my heating on yet and my bill today for the last quarter for gas is £67. I don't have any other gas appliances other than a hob. I thought that when you had the heating on it cut out once it got to temperature. Am I better to just put the water on when Ineed it?

Andy_WSM

Depends if you consider £5 a week for "on demand" hot water "expensive"?

Don't forget that by only turning the boiler on when you "need" hot water you will have to wait for up to an hour and still have to pay for the gas to heat it anyway, so the potential saving might only be £1, maybe £2 a week tops.

You will no doubt get many posts telling you to cut down the programmer times, but the reality is that once the tank is up to temperature the boiler will shut down regardless.

macman

If you have a conventional hot water tank then (within the time period set on the controller) the boiler will continue to heat the water until it reaches the temp set on the tank thermostat, which you can adjust yourself if the water temp is too high. The hours you set will depend on your own pattern of usage, but as long as the tank is well insulated then it shouldn't lose too much heat over a 5 hour period. You could set it down to say a 4 hour evening period and see if you still have the hot water that you need later in the evening-what you don't want is to have a full hot tank last thing at night that then has all night to cool down again before the morning cycle.
Putting it on when you need it will not work, because then you will have to wait for the tank to heat up.

penrhyn

I have a conventional Y plan Gas central heating system.
Thermostat on the hot water tank set to 60c, and run the boiler for a couple of hours/day.
The boiler is a 10 year old Ideal, and my costs are between £1 - £2 a week during the summer months for hot water. There is only me in the house mind.
So hot water only is costing me around £ 200 /year.
PS Top Tip - Even if your HW tank has spray on foam another jacket does not harm.

Cardew

You will probably find that up to £20 of that cost(for a quarter) is for the pilot light(assuming you have one)

There is much nonsense talked about savings to be obtained by only having the boiler on for 30 mins or so. A modern well insulated HW tank is tested to a British Standard and loses about 2kWh in 24 hours with water at 65C.

In practice it won't be at 65C for the whole 24 hours so probably 1kWh to 1.5kWh is typical. - £10 to £15 a year.

In any case that 'lost' heat isn't lost for most of the year as it warms the fabric of the house - which is why tanks are often in an airing cupboard.

Owain_Moneysaver

If you don't have a tank thermostat it would be worth getting one fitted, otherwise the system relies on the boiler thermostat which is wasteful. A 2 year old boiler should already have one though.

However it only takes me about 30 mins to heat up a tankful of hot water for a bath.

Pincher

If you have a look at recovery time for Heatrae Sadia Megaflo cylinder specifications, you will see timings of around 30 minutes, so one hour is plenty to get a full tank hot, unless you have a tiny 12kW boiler mated to a 300 litre cylinder, which would be wildly mismatched, but encourages condensing mode, so more efficient.

Anyway, when I'm alone in the house, I just have one hour of hot water around 5am by timer, so I get piping hot water in the morning when I wake up. The rest of the time, I just hit the boost button.

I love the Honeywell boost button, you get one hour per press, up to three hours. So set the timer for a minimum number of hours, for both heating and water, and just hit the boost button when you have guests and staying up late.

Yolina

I have a 20 year old boiler (no permanent pilot light) and a 210 litres tank. In summer, I run the hot water for 20 minutes in the morning - it is hot enough for a shower first thing, then what's left is sufficiently warm to use throughout the rest of the day for washing up, etc... in autumn/spring I run it for 30 minutes in the morning and in winter it's 40 minutes as obviously the water coming in is colder and needs longer to heat up. I also have a gas hob for cooking. I've used 411kw in the last quarter.

Cardew

Yolina wrote: »

I have a 20 year old boiler (no permanent pilot light) and a 210 litres tank. In summer, I run the hot water for 20 minutes in the morning - it is hot enough for a shower first thing, then what's left is sufficiently warm to use throughout the rest of the day for washing up, etc... in autumn/spring I run it for 30 minutes in the morning and in winter it's 40 minutes as obviously the water coming in is colder and needs longer to heat up. I also have a gas hob for cooking. I've used 411kw in the last quarter.

411kWh or 411 gas units?

How much was your bill?

Yolina

Cardew: 411Kwh - 13 imperial units. My bill was £24 - though actually free as I'm with Scottish Power on the Online NSC for gas, paying by variable quarterly DD which gets a prompt payment discount of £25/quarter and considering my low total usage over the year this is actually the cheapest for me.

Edit: I used 7661 KWh of gas during the previous 12 months