There have been plenty of times in the past when we’ve seen an exodus of shoppers from Ireland to Northern Ireland – particularly in the lead up to Christmas – simply because it was so much cheaper to stock up in Newry than in a local supermarket.

But is a trip north today a way for households to squeeze a saving out of their weekly shop?

What’s in the basket?

We need your consent to load this rte-player contentWe use rte-player to manage extra content that can set cookies on your device and collect data about your activity. Please review their details and accept them to load the content.Manage Preferences

To try to compare prices, we’ve picked up a few fairly every-day groceries in Dundalk, and then taken a trip up the road to Newry to see how it differs in price.

In the basket was some bread, milk and eggs, as well as some pasta, chicken, vegetable oil and toilet roll…

There’s also one "luxury" item – a bottle of Prosecco.

For the sake of comparison the prices were on the exact same products in the exact same retailer.

The prices were also the standard ones – so no special offers, discounts or deals were factored in.

After that the big variable is the exchange rate – which, of course, changes by the minute.

To make matters more complex, the rate that you’re seeing on an app isn’t necessarily the same one that your bank will give you when you buy something on the other side of the border, nor is it necessarily the price that the retailer was dealing with when it was importing products.

So to try to iron out any sudden changes, the rate used here was an average for the past month.

So which side was cheaper?

What’s interesting is that there’s no overall trend; no side of the border was consistently cheaper than the other.

In actual fact, it was a bit of a mixed bag.

Some products were cheaper in Dundalk, and others were cheaper in Newry and, overall, the price of everyday items largely balances out.

But hidden within that are some significant differences.

What products had the biggest price difference?

When it comes to eggs and milk it’s actually fairly comparable.

A litre of own-brand, whole milk cost €1.05 in Dundalk and was the equivalent of €1.10 in Newry. So very slightly dearer, but not by much.

The eggs I bought in Dundalk were more than 8% dearer than the equivalent in Newry, though, so you’re losing about 15c on six, large free range eggs.

Meanwhile the chicken was close to 30% dearer in Dundalk.

Why is that?

There are a couple of general factors that might be at play – for example VAT is slightly lower in Northern Ireland than it is in Ireland; business rates are lower too.

There’s also probably a benefit coming from the 'economies of scale’ – the fact that retailers in the North are part of a massive UK chain, compared to a relatively small business in Ireland.

So if the retailer in the UK goes looking for a supplier of chicken for the entire group, for example, they’re placing a much bigger order – which gives them a lot more leverage in the price they pay per kilo.

They probably also have more suppliers to negotiate with than they would when looking for when the Irish business is looking for an Irish producer.

But perhaps the most important factor is just how competitive the Northern Ireland grocery market is.

In the Republic there is the Big Three – Tesco, Supervalu and Dunnes – as well as the discounters of Aldi and Lidl. Together they account for about 91% of our total grocery spending each month.

In Northern Ireland, though, there’s Tesco, Supervalu, Dunnes and Lidl; as well as Asda, Sainsburys, Morrisons, Iceland and the Co-Op.

And when you have a small market with that much competition that helps to drive down prices, especially on the daily basics that almost all shoppers are picking up when they come into the store.

But despite the many reasons why Northern Ireland would be cheaper, there are often cases where it simply is not.

One essential that was considerably dearer in Newry than in Dundalk was bread.

A white sliced pan was 90c in Dundalk, and the equivalent of €1.33 in Newry… that’s nearly 50% higher.

You might have assumed it would be the opposite, especially because a lot of the flour used to make bread here comes from the UK, and so is subject to tariffs post-Brexit.

But what could be skewing this is supermarket’s love of the so-called loss-leader.

This is where they sell an essential product - like bread or milk - at cost or even at a loss, as a lure for shoppers.

The hope then is that they go on to spend money on other products while they’re there.

What other products cost more in Northern Ireland than in the Republic?

Pasta had the biggest price difference out of all the essentials checked.

In Dundalk, 1kg of dried spaghetti was €1.09, while in Newry it was the equivalent of €1.79… so a 70c, or 64% difference.

What we’re seeing here is likely the Brexit effect – because durum wheat, which is used to make pasta, generally comes from Italy and France.

Due to Brexit, a British firm buying Italian produce now faces additional costs and tariffs and that goes towards explaining why pasta is more expensive in the UK.

In theory, the Northern Ireland protocol should allow for Northern Ireland retailers to avoid tariffs on the likes of Italian goods, but if it’s being imported to mainland Britain by the British-registered company, they get much harder to avoid.

And it’s a similar story for vegetable oil.

Vegetable oil here is almost entirely made up of rapeseed oil – which the UK is a producer of.

However, there have been major harvest issues there in recent years – and because of Brexit - supplementing their own output with oil from places in the EU has become much more expensive.

As a result, the price in Newry was 45% higher than in Dundalk.

You’re paying €1.39 a litre in Dundalk, but more than €2 in Newry.

So when you put all of that together – what are you spending?

The cost of those seven items together was €20.15 in Dundalk.

The price of the same items in Newry was roughly €18.72 – so slightly cheaper, to the tune of around €1.40, or 7%. Probably not enough to get people to head for the border en masse.

However, those comparisons are largely based on own-branded goods. When it came to a number of branded products, Newry was consistently cheaper.

A large bar of a well-known chocolate was 33% cheaper in Newry, for example, while a multipack of crisps cost 21% less.

Both of those were British brands, which may be part of the reason for that.

Elsewhere, a packet of nappies was about 8% cheaper, while a box of detergent was 23% cheaper.

Meanwhile, a can of a well-known brand of men’s deodorant was more than 48% cheaper in Newry – nearly half the price.

And there is one other item in the shopping basket that we haven’t spoken about yet – and that’s our luxury item, the prosecco.

What was the difference there?

The bottle in question is essentially an own-brand bottle of prosecco – it’s made specifically for the retailer used, so not a high-end option by any stretch.

In Newry it cost just under €10 - €9.82, to be precise.

In Dundalk, it cost €20.

So that’s double the price, for the exact same bottle of fizzy wine.

Why is there such a huge difference?

There are a couple of factors at play.

For a start, Ireland’s excise is a good bit higher than the UK’s.

It’s a little bit higher for beer, but it’s a lot higher for spirits and wine.

In the case of this bottle, it’s about 19% higher – if it was a stronger wine it would be nearly 26% higher.

For spirits, there’s a 22% difference in the excise applied.

And that higher rate of excise is on top of the slightly higher VAT rate mentioned before.

But the other big factor is minimum unit pricing.

That’s a rule that came into effect in Ireland at the start of the year, and it means that retailers cannot sell alcohol below a certain price, which is based on the amount of alcohol that’s in the can or bottle.

There’s no equivalent law in Northern Ireland at the moment, though there have been consultations about introducing one.

At €20, this bottle of Prosecco is priced well above the minimum price – but one of the effects of the minimum price is that it seems to have pushed other prices higher.

That’s, in part, because brands might not want to be in the same price category as the cheapest option, and in part because they simply can – the higher price won’t look so out of place now.

It’s not just Prosecco where there’s a difference, either. It’s across the board in the alcohol line.

A box of 20 bottles of a popular beer was about 35% cheaper in Newry, a bottle of vodka was about 23% cheaper.

Is that going to be a worry for retailers?

Almost certainly - a lot of retailers in Ireland will be nervous about that price difference, particularly as we head towards Christmas.

As we know, people will often stock up on alcohol in the run up to Christmas – and retailers normally respond to that by bumping up the amount of booze they stock. They bring in the big slabs of cans, and they also put special offers on different products like spirits and wine.

But they’re just not going to be able to do that, certainly not to the same extent, this year.

For example, while the large tray of cans is normally a Christmas standard, at least one retailer is planning to do without them for the first time.

That's because they would have to be priced somewhere in the €40-45 region - compared to the previous norm of €20-25.

The assumption is that people simply will not buy them at that price.

But the fear will be that shoppers in the Republic may look to go north to stock up instead – and while they're there they may decide to just do their whole, big Christmas shop too.

It might not be cheaper, but if they’re already there it will be handy.

The one thing that might go in favour of retailers in the Republic at the moment is the high price of petrol and diesel.

After all, some may crunch the numbers and find that the amount they’ll spend to take the trip up and back undoes any saving they’d make on their drink when they get there.