Heating water. Gas vs immersion.

Brego888

Does anyone have any ideas on the cost differences for heating domestic water tank between running the gas boiler or using the electric immersion?

Red Alert

Gas will win on energy, assuming that the cylinder and boiler stats are set correctly.

Brego888

Brand new water cylinder with dual immersion heating elements and recently serviced gas boiler.

ted1

It depends how much you water you need.

Gas is 1/3 the price but suffers losses size as the heat has to travel the pipes upto the tank, also if you can't isolate the hot tank then you are also heating the rads so could three times. More gas. An immersion has more control.

the_syco

If using a hot-water tank, ensure it's insulated correctly, so it doesn't leak so much heat. Our current "hot press" is rarely that hot since the new (insulated) tank was installed.

rasgav

Gas is much cheaper and much, much more efficient in our house.

littlemissfraze

Assuming you are using a 3kW immersion for 2 hours a day, that's 6kWh.

Electricity - 6kWh x €0.1878 = 1.13 x 365days = €412 per annum (assuming you heat it for 2 hrs per day)
Gas - 6kWh x €0.076 = 0.46 x 365days = €168 per annum (add 20% for boiler efficiency and pipe losses) €202
Oil - 6kWh x €0.0943 =0.57 x 365days = €208 per annum (add 20% for boiler efficiency and pipe losses) €250

So in summary heating you hot water by your central heating system will save you €100s if you use it a lot!

L1011

littlemissfraze wrote: »

So in summary heating you hot water by your central heating system will save you €100s if you use it a lot!

Assuming the tank is isolated. I've had no way in this house or my last of heating just the tank - despite the gas boiler in the previous house having functionality for it the cowboy builders never plumbed it properly.

If you end up heating the radiators too you'll use a lot more energy and probably be waiting quite a while too.

littlemissfraze

L1011 wrote: »

Assuming the tank is isolated. I've had no way in this house or my last of heating just the tank - despite the gas boiler in the previous house having functionality for it the cowboy builders never plumbed it properly.

If you end up heating the radiators too you'll use a lot more energy and probably be waiting quite a while too.

It's a pity so many houses are plumbed this way. Can you close the valves on all the radiators to isolate them during summer months?

L1011

littlemissfraze wrote: »

It's a pity so many houses are plumbed this way. Can you close the valves on all the radiators to isolate them during summer months?

Yes, but you're still heating a huge bulk of plumbing in the way.

Will be properly re-engineering the system at some point but there'll be solar water put on the fairly large south facing roof at that stage also, meaning not as much need for heating water in the summer anyway!

ted1

littlemissfraze wrote: »

Assuming you are using a 3kW immersion for 2 hours a day, that's 6kWh.

Electricity - 6kWh x €0.1878 = 1.13 x 365days = €412 per annum (assuming you heat it for 2 hrs per day)
Gas - 6kWh x €0.076 = 0.46 x 365days = €168 per annum (add 20% for boiler efficiency and pipe losses) €202
Oil - 6kWh x €0.0943 =0.57 x 365days = €208 per annum (add 20% for boiler efficiency and pipe losses) €250

So in summary heating you hot water by your central heating system will save you €100s if you use it a lot!

That's an ideal world scenario. Lots of existing Systems can't isolate the hot tank.
I find an electric shower to be the most ecomonical it only heats the water required.

littlemissfraze

Even if you had 50m of uninsulated copper you would still be better off using a gas boiler if you have one:

Heat loss of uninsulated 3/4inch pipe = 60W/m -> 50m x 60W/m = 3000W (3kW)

Gas Boiler - (3kW+3kW)x2hrs = 12kWhrs x €0.076 = €0.912 x 365 days = €332.88 (allowing an extra 20% gives €399.46, still cheaper than electric example above)

Idbatterim

in my family home, we simply have a combi boiler, there are no tanks. You simply open the hot water taps and receive instant and unlimited hot water... Op I take it you are on a gas mains and not using LPG? My family holiday home requires plumbing soon and we are thinking of using electric on night meter... (as we are not on a gas mains)

L1011

littlemissfraze wrote: »

Even if you had 50m of uninsulated copper you would still be better off using a gas boiler if you have one:

Heat loss of uninsulated 3/4inch pipe = 60W/m -> 50m x 60W/m = 3000W (3kW)

Gas Boiler - (3kW+3kW)x2hrs = 12kWhrs x €0.076 = €0.912 x 365 days = €332.88 (allowing an extra 20% gives €399.46, still cheaper than electric example above)

There's also the cold water *in* those pipes, though, as well as loss from the heat exchanger.

Proper combo boilers are an entirely different scenario.

Michael D Not Higgins

Idbatterim wrote: »

in my family home, we simply have a combi boiler, there are no tanks. You simply open the hot water taps and receive instant and unlimited hot water... Op I take it you are on a gas mains and not using LPG? My family holiday home requires plumbing soon and we are thinking of using electric on night meter... (as we are not on a gas mains)

I have a combi boiler as well. Great yoke for instant hot water at lower cost.

ted1

littlemissfraze wrote: »

Even if you had 50m of uninsulated copper you would still be better off using a gas boiler if you have one:

Heat loss of uninsulated 3/4inch pipe = 60W/m -> 50m x 60W/m = 3000W (3kW)

Gas Boiler - (3kW+3kW)x2hrs = 12kWhrs x €0.076 = €0.912 x 365 days = €332.88 (allowing an extra 20% gives €399.46, still cheaper than electric example above)

Your heating a different quantity of water. It really boils down to how much water is needed.