Kerosene usage after installing an Eddi

Solar and eddi heats hot water in summer when kerosene boiler is off. Solar PV will not heat home in summer nor winter, it's just a way if reducing esb bill for heating water and other electric consumers.

Most people don't heat their hot water with oil in the summer. On some systems that are zoned you can heat hot water only with oil, and some people might do that for 15 minutes a day in summer.

Solar batteries are generally expensive, they don't generate anything, they just store already generated power so you can make better use of power in evenings. It's totally unrelated to heating your home in winter. Typically solar systems break even after 7 years but it depends, mostly on how much you overpay for the solar system as prices vary a lot. I believe the grant for a battery is gone.

I have a 4.2kWp system installed since November with an Eddi. I use gas 365 days to heat water for 3-4 showers a day and during summer it costs 30-40 per month. For the first time since installation over the last two days, there was enough excess from solar to heat until the immersion cut out and it exported a few kwh. It was only enough water for about 2 showers though what I didn't realize until was that the boiler heats the full hot tank but the Eddi can only do about half as the immersion is short.

How is the Grant Vortex working out as I'm thinking of replacing our 20 plus year Firebird next year.

Hi. Is the SEAI grant available for the boiler change and if so did you avail/was it worth it?

Electric heaters and smart plugs are becoming more and more of a simple and clever option every day.

A decent array couid make a good dent in oil consumption during spring and autumn months.

Still researching, pre-purchase.

From the Solar FAQ:

"The general thinking is that EDDI’s while they are a useful and convenient device, for €500 or so, it’s unlikely that you will get that money back in the lifetime of the device. If you think about it, €500 will probably pay to heat your immersion tank once a day everyday for 3 years. "

I'm confused about the above. By that logic, aren't you getting your money back in 3 years? Is the lifetime of the EDDI shorter than that, or do I misunderstand the statement?

Interested in how this might work - can you elaborate? e.g. how can you combine electric heaters with ones heated by oil boiler central heating? just plug in portable heaters into the main living areas, and rely on the room stats to keep the central heating off (saving oil). Then once you've used up all the power from the panels, you somehow have the electric rads turn off (is that what a 'smart plug' does?) .

But if you use up all your juice on heating electric rads in Spring/Autumn, aren't you depriving the other appliances (dishwasher, kettle) of using the free solar juice, thus defeating the purpose?

New to all this, so happy to be schooled on it.

With kerosene, its a very indirect way of heating, and the loses due to in-efficiency will build up quite quickly:

A fire, to heat water, to be pumped through pipes outside the system (outside the boiler/cylinder), that heat exchange with different water...

The immersion is very direct, practically 100% efficient.

Take 1l of kerosene, it gives 10.35kwh

A condenser boiler has a stated efficiency of say 90%. BUT, that rating is often under ideal conditions: certain water temperatures, pressure, and host of other factors. So the real-world efficiency will be less. Will it be 80%? Let's be optimistic and say 85% for this example.

The water that the boiler heats is then circulated to the cylinder, via pipes that will have their own losses, and a heat exchange in the cylinder. This could lead to another up to 30% loss, but thats probably a more extreme example with bad lagging/long distances. Lets take it as 15%.

And then you still are using electricity to power the boiler and the circulating pump.

Add all this up, can see that 1L of kerosene (costing approx 1.80e) being the equivalent of the 6 or 7 kwh of solar excess that the EDDI put into the cylinder yesterday.

(I accept that people will have different takes on the efficiencies I gave as example above. IMO they are generous for kerosene, but open for debate)

Of course this is just a comparison of kerosene to "free" excess solar. Comparing an immersion on a timer running from 2am to 5am at 5 or 6 cents a kwh (bord gais EV plan) is a different comparison completely...

The Gov/Green Party want to push us all to solar think of all the tax they are going to lose out on how will they make up the difference.

While there is a lot of truth in what you say you have definitely massaged the figures in favour of the immersion. Most people will hopefully never pay 1.80 for oil and this is probably a temporary glitch while more oil production comes online and most people don't pay 5-6c/kw & there are other costs associated with going on that EV tariff. 2-5AM is not an ideal time to heat it, unless you get up at 5. A lot of the losses from the boiler contribute to heating the house

While I agree that for some people it be at different rates, I don't thinks it's a fair response to say the figures are massaged.

Everyones setup may be different. That's what I meant in acknowledging that everyones take may be different.

What kind of boiler do they have?

Where is the boiler situated? Inside/outside/shed/garage/etc

How long are the pipes?

Are they well insulated, and is it practical to upgrade the lagging on them? (buried? under that nice floor that you don't want to lift?)

Are the pipes mostly inside or outside the insulation envelope of the house?

Maybe some are still gunbarrel? (and again is it practical to replace them)

Is the cylinder even inside the insulation envelope of the house?

So, yea, while good answers on the above will give a good ratio, it may not be the case for everyone.

One persons 8 to 1 may be another's 7 to 1. One persons losses will go back into the house, another's will be gone outside/underground.

And on top of all that, this is a forum after all, full of great opinions and interpretations, and its great to see a conversation on it.

I've no idea, or take really, on whether prices will go up or down, short or long term. I do know that if needed oil today, the local supplier is charging 899 euro for 500L (1.80), and the best on cheapestoil.ie for the region is 1.71 for 500L right now. I do hope you're right that its a temporary glitch and that most people won't be paying that, but can only go on what its going for today... Sure, you could a get cheaper if you get a 1000L order, but if you're hoping it comes down, maybe would stick to 500.

I wasnt really going there on the smart meter rate, but will respond to the not ideal comment : while its true that it won't suit some people, and there are costs associated with that plan (higher standing charge for one), there are also some people that it will suit. And while heating an unlagged, or red-jacket-lagged, cylinder at night is unlikely to be ideal, heating a factory lagged cylinder at 3am is great (for a fraction of the price of other times). I had that EV rate for a few weeks before getting solar, set the old rotary time-clock to heat the bath element from 3am to 5am, and this plenty-covered morning (8am) showers, and if no showers that morning it kept a decent temperature through much of the day. Will be doing it again come Nov/Dev.

Anyway, going leave it there.

The state got a lot more from VRT in 2007 than they got in 2020. The lost billions by switching to the CO2 system. They never looked into recouping that from the motorist. Even when the times were dire and this country lost its economic sovereignty

Not saying they will not try to recoup it this time, they probably will. But it will take a very, very long time to introduce km based taxes. I'd say 2030s at the earliest.