Electric immersion vs gas heating water?

masterboy123

Hi,

We get hot water via the Gas Heating. But there is also an option to heat water using the electric immersion.

The electric immersion is always quick, but I am wondering which is a cheaper form of getting hot water in winters?

The electric immersion is connected to solar panels also.

Thanks

magicbastarder

what are you heating the water for?

reason i ask is AFAIK it's more efficient/cheaper to heat water with gas - but if we use gas it heats the whole tank; however the immersion allows you an option to heat just the top of the tank.

the_amazing_raisin

Electric heaters are more efficient, but also generally more expensive to run because electricity is more expensive per kWh than gas

When you say the immersion heater is connected to solar panels, what exactly do you mean. Are they solar PV panels which generate electricity, or solar tubes which heat water?

If it's PV you should have an inverter somewhere to convert the DC electricity from the panels to AC for the house to use

You might also have a device called a solar diverter, one popular one is called Eddi by MyEnergi

This replaces your immersion controller and will heat the water using solar power when there's excess power available (you're generating more than you're using)

masterboy123

It's solar PV which generates electricity.

I am attaching picture of the inverter here.

10-10-20

Are you getting a FiT (feed in tariff) off your provider and if so, what price it is? And what price is a unit of gas on your contract? You might find that it's still cheaper to heat the water using gas if the FiT is above the unit rate of the gas (+ losses) cost.

the_amazing_raisin

Cool, so you probably know the drill, the inverter will try to meet the power needs of the house from solar power when it's available

Any shortfall in power needs will come from the grid, and if you're generating more than you need this is fed back to the grid (and you should get paid for it)

Since you didn't mention batteries, I'm assuming you don't have any?

You might benefit from a hot water diverter which will sense energy being sent to the grid and switch your immersion heater on to use up the extra energy

The trick with the diverter is that it'll regulate the amount of power used by the heaters to stay within the amount of solar power being generated

For example if you're generating 1.2kW and your immersion is usually rated for 3kW, you'll end up using 1.8kW from the grid if you switch it on manually. The diverter will limit the power used by the immersion to just below 1.2kW to avoid taking power from the grid

It's worth checking out the renewable energy forum as there's many other ways to maximise your use of solar power and lots of good threads there with advice

masterboy123

https://www.boards.ie/discussion/comment/121132672#Comment_121132672

No, we don't supply electricity back to Electric Ireland. Our builder told us its a complex procedure and not worth it. We live in a new estate (2 years old).

Gas unit price = €0.1346.

Electricity unit price = €0.4358 with free electricity on Sunday.

We don't have batteries on our Solar PV system. I doubt there is any diverter either.

10-10-20

https://www.boards.ie/discussion/comment/121133834#Comment_121133834

Ok, I see. What size solar panel installation do you have in that case?

And do you have an Eddi or iBoost in the hot-press?

the_amazing_raisin

https://www.boards.ie/discussion/comment/121133834#Comment_121133834

Your builder is an idiot, it's literally one form for any electrician to fill out. Google an ESBN NC6 form

10-10-20

https://www.boards.ie/discussion/comment/121134203#Comment_121134203

If it turns to be like 2kW of solar power, then I can kinda see his point. Except of course that it limits future expansion of that array if the NC6 is not in place as no electrician would want to touch it and submit the NC6 on the basis of the builder's own install.

masterboy123

https://www.boards.ie/discussion/comment/121133895#Comment_121133895

It's 6 solar panels on the roof with Solis inverter.

We don't have Eddi or iBoost. It is just an ordinary switch to heat water.

10-10-20

https://www.boards.ie/discussion/comment/121134387#Comment_121134387

So roughly 2000 to 2400kW of panels. Ok, no, that's bonkers! How many other houses in the estate are like this?

If it is what you say then you're loosing on the double as you can't reliably direct the generated solar power into the cylinder, nor are you getting paid for the solar power which you are releasing into the grid. That's just box-ticking by the builder with no meaningful function behind the solar. Depending on how you calculate that, you could be losing around 3 EUR per day during the Summer months, and having to pay to heat the tank when the sun goes in.

You'll need to find out whether that type of setup is acceptable against the building regulations and then decide on whether to approach the builder from there. If the system is not compliant then I'd be looking to do that as a group of owners with a view to going legal in a class-action type way through a solicitor.

the_amazing_raisin

Agree 100% with @10-10-20, this was some serious corner cutting by the builder, trying to comply with the regs while not doing anything useful for the homeowners.

You and everyone else on the estate has been losing FIT payments for something like 2 years now, with all the energy price increases in the past year that's some hard pill to swallow

There's probably grounds for legal action there, but in the meantime I'd recommend getting a diverter installed and seeing if the electrician will do a retrospective NC6 form to get you the FIT payments

masterboy123

https://www.boards.ie/discussion/comment/121134423#Comment_121134423

All the houses in the estate are the same. We were told that solar PV will provide some energy to heat water using electric immersion.

The solar PV system was installed by "Clean Energy Ireland". When we moved into the new house, the Solis inverter was showing an Error and a Red light. The builder contacted the Clean Energy, and an electrician came to restart the panels and showed us it was creating energy.

I think the microgen system wasn't there three years ago (we moved in late 2020).

Now, do I contact Clean Energy and ask for the diverted to be installed? How much do I need to pay roughly?

10-10-20

https://www.boards.ie/discussion/comment/121136962#Comment_121136962

An Eddi or iBoost is around 550 EUR for the equipment alone, but not tricky to install. So maybe another 250 or thereabouts for the install. If you have thoughts on getting a car charger it may be worth while having one installed at the same time so that the systems can be linked and you can avail of the charger grant.

Talk to the electrician at the time about getting the system submitted to ESBN under NC6, it could be worth your while during the summer months as you'll get credit for unused electrical untils instead of giving them to your energy provider for free. He'd probably charge a fee for an inspection and the paperwork.

Hope this helps.

the_amazing_raisin

https://www.boards.ie/discussion/comment/121136962#Comment_121136962

The inverter will try it's best to meet the needs of the house but without some intelligence on the consumption it becomes difficult

Your appliances generally draw a fixed amount of energy, a kettle typically draws 3kW for example

So if your panels are generating 2kW then 1kW will come from the grid

The idea then is to try and manage your consumption to keep it within what your panels are generating. You can do this manually by obsessively watching the output and turning stuff on when there's excess power, or using some automation

I think it's pretty obvious which one most people choose 😁

An Eddi is one option, batteries are another, a smart EV charger is another

It's worth saying that I'm pretty sure the NC6 form isn't optional. There wasn't a Microgen payment in 2019, but I'm pretty sure the installer still has to file the NC6 form with ESBN

It's worth contacting them and asking about it, maybe they'll file it for free since they should have all the test data to hand.

Unfortunately you won't get the payments backdated, they only start from when the NC6 is filed

The Microgen payment is another way of getting value out of the panels, they mean electricity fed to the grid isn't wasted

However it's worth remembering that the money you get from exporting is less than the cost of buying electricity from the grid. So it's generally better to self consume than export, unless you've got a huge house battery you can charge from night rate electricity

masterboy123

https://www.boards.ie/discussion/comment/121136986#Comment_121136986

It is pricey alright, in the region of 1000 euros.

I might hold off for now and re-assess next year.

Thanks to everyone!

G Dog

I have a similar query, so I hope it's ok to add to this post. I have a 5kw hybrid solar system with 8.6kw batteries. I recently switched electricity provider to Pinergy, as they have a very low EV Drive tariff of 5.45c per KW between 2am - 5am. I have my inverter set to charge my batteries during this time, so I'm barely paying for their standard rate of 37.03c per KW.

I'm trying to work out the best way to heat the full water tank. Currently, I have switched off the gas, and manually set the iBoost to heat the water at the 5.45c rate with the 3KW immersion heater, but as this only heats the top half of the tank, sometimes we run out of hot water in the morning. We have the same issue in the evening when the solar has heated only the top half of the tank and we need to run the bath and have showers. We don't want to constantly worry if we have enough hot water.

A plumber has suggested installing an external immersion heater that will heat all of the water as it enters the tank. I'm wondering is this a good idea, as I will be using a lot of energy during the day that I could be exporting to the grid at a rate of 25c per KW. Bord Gais charge me 8.938c per unit. Can anyone advise if this extra immersion is a good idea, or would I be better going back to gas to keep the water hot, so I can export more surplus electric to the grid, rather than using it to keep the entire tank constantly hot? Maybe I should stick with the current immersion and use it to heat half the tank at the low EV rate, then set a short top up with the gas in the mornings and evenings?

Obviously, I would only manually be setting the iBoost diverter to heat from the mains during the summer, as the central heating will be heating the water in the colder months.

Thanks!

the_amazing_raisin

https://www.boards.ie/discussion/comment/122250177#Comment_122250177

I suspect you could connect the external immersion heater to the iboost, so it'll only activate at certain times

Another option might be a destratification pump to circulate the hot water at the top of the tank to the bottom and even out the temperature?

A simpler idea in the short term could be to use the immersion to get half the tank hot and then top it off when the gas boiler afterwards

The tricky part is working out the difference in cost of using electricity versus gas to heat a tank of water

I'm not sure myself how to do that because you need the boiler efficiency to figure out the equivalent kWh of gas used to put 1kWh of heat into the water, and also convert a kWh of gas to m^3 since that's what you pay for

asharkman

Hi all, I'm looking at this as well.

I'm planning on getting a solar installation. I don't have an EV, was going go with a hybrid inverter so if I did want a battery in the future I could.

Was originally going to go with the eddi diverter, then the solar guys suggested a timer on the emersion was a better solution, just turn it on for an hour at 12/1/2 o clock.

Then I was thinking, what's the point in any of this, with Energia, you can buy in electricity for .28c and sell it out for .24c.

My gas with Energia at the moment is like 10c per unit.

So, correct me if I'm wrong, but surely its never worth my while to use the Eddie Diverter, it seems like your better off at all times to sell back to the grid, at these prices.

Am I missing something?