Gas Vrs Electric combi boilers :which is cheaper to run ??

vessy

I am seriously considering installing one of these to replace a 40 year old lpg boiler, I'm presently paying around 7.3p/kwh for lpg, this supplies an ideal Mexico floor boiler which I'm guessing is probably 70% efficient, this gives me a cost of around 11p/kwh (inc tax). My elec is 9.3p/kwh (inc tax). Last year I used roughly 13,000 kwh to heat my house & water, this is a potential saving of £220 per year, even more as I'm sure lpg will increase again very soon. I can also block up the huge air brick next to the boiler which will help.

Would love ground source but can't afford the 10k outlay.

Cardew

Divads wrote: »

I have Gas Central heating modern gas condensing boiler. An open vented system with 2 tanks both indirect with emersion heaters. I use economy seven to heat these at night for hot water during day each tank being used separately. Topping up one tank with gas if nescessary. I have just had installed a Solar PV system and am looking for a way of using its spare electricity to top up the domestic hot water tanks.

Does any one know of systems able to do this? Both emersions are 3kw.

Divad

Welcome to the forum.

Firstly if you go to the Green' forum on MSE there is discussion about devices that 'match' the demand to solar generated output. However they are very very expensive and of little practical use in a domestic situation.

Others have spoken about getting a 1kW immersion heater. That said with the widely varying solar output it will be a nightmare to try to match the output to demand.

In any case you will only save money at the gas rate of around 4p/kWh. Even if your panels are producing 2kW the immersion heater will draw 1kW electricity from the mains @ 14p/kWh?? for E7 day rate so you will be losing money.

Bottom line it is a non-starter.

On a separate subject, why use E7 at night to heat your water? You presumably are paying around 5p/kWh for E7 cheap rate, and your gas with a modern boiler's efficiency should be less than 4p/kWh.

On top of this you are paying a premium for your daytime electricity on E7.

cornish-saver_2

Hi,
I've recently been given an 'electric smart meter' (connects to main electric supply to give real time electric usage in house).

I couldn't understand why we seemed to have a high constant electric use even when nothing much electric seemed to be switched on! I went round the house switching things on and off and checking the smart meter to eventually find that my Gas combi boiler which needs electric to run digital display is using 150 watts per hour. That’s without any heating on or hot water being drawn, no pumps or fans, JUST DIGITAL DISPLAY.

3.6 kWh per day.

I pay 10p per kWh, so am spending 36 pence per day.

That's a whopping £131.40 per year just to have my Gas combi boiler switched on, even if I don't use the heating or turn on the hot tap!!!

Is this normal?

If you have a gas combi boiler and a smart meter please check and add what yours is.

I've got a RENO 'High efficiency combination boiler' HE30C.

Thanks,

macman

If you are talking about a clip on energy monitor (not a proper smart meter, which is a replacement for your standard meter) then they are notoriously inaccurate, especially at low readings.

cornish-saver_2

Yes I do have a clip on energy monitor, but as I stated I went round the house switching everything on and off to check the response of the monitor. High energy items like, kettle, electric shower and hover showed a very high usage on the monitor (2.545kWh for the kettle). Low energy items would show little if any change in meter reading.
Even if you want to allow for the inaccuracy of the energy monitor by as much as 30% (which you would have to allow for inaccuracy 30% below AND 30% ABOVE my reading).

My electric tariff is also on the lower side of the national average, so I still think for a boiler which calls itself “High efficiency” using this amount of eclectic just to be switched on is unacceptable. For a low income family with an electric key meter on a high electricity tariff they could be spending up to £200 a year.

To just dismiss this as ”notoriously inaccurate” is flippant, show us some accurate readings!

macman

According to the manufacturer's tech spec, the HE30C requires 145W, it doesn't specify whether that's when running or when idle.
It's not just the display that is being powered; all the other circuitry inluding the PCB, timer etc remains live in order to respond to any call for heat.

cornish-saver_2

Thank you for finding that info for me, good to know that's the normal power usage for this boiler and not that mines got a fault.

do you know if that is an average power usage amount for a gas combi boilers?

Cardew

macman wrote: »

According to the manufacturer's tech spec, the HE30C requires 145W, it doesn't specify whether that's when running or when idle.
It's not just the display that is being powered; all the other circuitry inluding the PCB, timer etc remains live in order to respond to any call for heat.

Surely that sort of consumption would include the pump running???

I can't see electronics using anything like that amount.

Shogun32

What people don't realise when it comes to things like electronics is that every little thing adds up. A few Watt here and a few Watt there make a big difference.

In the case if a boiler (Just as an example) you might have 3/4 temperature sensors at 5W each, 2/3 flow switch at 5W, an electric ignite switch at 10W, a pump at 50W, a display at 20W. Add all that up and you have 115W without even blinking, this doesn't take into account all the circuitry on the PCB.

Another example is in my PC at home i have a 750W PSU to power the thing and all it's components!

So you can see how easy it is to build up a power hungry boiler/machine.

Granted the boiler would be running idle for a big part of the day when hot water/heating isn't required when people are out at work/school, but even if it's idle it can still use 60% of that Wattage waiting to kick in on demand.

Cardew

Shogun32 wrote: »

What people don't realise when it comes to things like electronics is that every little thing adds up. A few Watt here and a few Watt there make a big difference.

In the case if a boiler (Just as an example) you might have 3/4 temperature sensors at 5W each, 2/3 flow switch at 5W, an electric ignite switch at 10W, a pump at 50W, a display at 20W. Add all that up and you have 115W without even blinking, this doesn't take into account all the circuitry on the PCB.

Another example is in my PC at home i have a 750W PSU to power the thing and all it's components!

So you can see how easy it is to build up a power hungry boiler/machine.

Granted the boiler would be running idle for a big part of the day when hot water/heating isn't required when people are out at work/school, but even if it's idle it can still use 60% of that Wattage waiting to kick in on demand.

Welcome to the forum.

You might have a 750W power supply on your PC(as mine has) but even when running it is normally consuming about 110W - and of course next to nothing when hibernating!

Personally I think your estimates of consumption for the electronics are way too high(not for the pump) A 20W display? That is enough power to melt a display.