Generators for Sale Ireland: Sizing, Rules, and Buying Guide

Anyone who has watched an Irish winter storm knock out the power knows the scramble: candles out, phone battery falling fast, and the neighbour’s generator already humming. That scene is why DoneDeal — the Irish classifieds site — carries more than 4,500 live generator ads at any given moment, and the practical questions are simple: what size actually covers your house, how the 80% rule works, and where the best new and used deals tend to live.

Generators listed on DoneDeal Ireland: 4,574 ·
Starting price for a new 6.5 KVA generator: €495 ·
Top brands available: Honda, Loncin, SIP, Jefferson ·
Average home power requirement in Ireland: 5–7 kW

Seven numbers capture the Irish generator market in one frame: what homes need, what brands dominate, and what typical new and used prices look like right now.

What size generator do I need to power my house in Ireland?

Start with what you actually need to keep running when the grid drops — not every socket in the house. A typical Irish home backup plan lands in the 5–7 kW range, enough for lights, fridge, broadband, and heating controls. That bracket shows up clearly in the portable generator range at MicksGarage (Irish auto and DIY retailer), which starts at 700W and runs up to 6.5kVA.

Will a 15 kW generator run a house?

• 15 kW is roughly two to three times a typical Irish home’s essential load
• Powers a medium-sized house with most appliances — if you stagger the heavy draws
• Usually a diesel or PTO unit rather than a portable petrol model

A 15 kW generator can run a medium-sized house, including kitchen appliances, a water pump, and most extras, as long as you don’t switch on the kettle, tumble dryer, and shower at exactly the same moment. That capability is covered by suppliers like Dermot Casey Sales (Irish equipment supplier), whose range runs from compact inverter models up to diesel and PTO units.

What size house will a 20kW generator run?

• 20 kW suits large houses with electric heating, water pumps, or home offices
• Provides enough headroom for most appliances at the same time
• Fuel burn and noise grow with capacity — not an idle backup choice

A 20 kW generator is enough for a large house and outbuildings, including electric ovens, showers, and workshop equipment. For most Irish homes that is more capacity than the essential-load list justifies. If you genuinely need that headroom, the used market on Machineseeker Ireland (used equipment marketplace) is one place to compare heavy sets.

The implication: size from your essential-load list, not from the house’s floor area. A small petrol portable covers the basics; the 15–20 kW classes exist for homes with electric heating, pumps, or workshops.

What is the 80% rule for generators?

Generators are rated for an output they can hold briefly, not as an endless supply. The 80% rule is the standard safety guideline: never run a generator above 80% of its rated capacity for sustained use. A 5 kVA generator, in practice, becomes a 4 kVA generator once you respect the rule.

What is the 20/20 rule for generators?

• 20 amps is the current where voltage drop over distance starts to bite
• 20 metres is the guideline maximum run for a high-draw appliance
• Applicability varies with cable length and load — longer runs need heavier cable

The 20/20 rule addresses voltage drop over cable distance: at around 20 amps over 20 metres, the voltage falls enough to matter for sensitive or motor-driven equipment. Keep heavy-draw appliances closer to the generator, or use a thicker extension cable for longer runs.

What this means: the 80% rule protects the generator, and the 20/20 rule protects the cable. Most households only need the first; site work and outbuildings bring the second one in.

What are the downsides of using a generator?

Generators produce carbon monoxide, noise, and a maintenance list — three costs that don’t show up on the price tag. The CO risk is the one that matters most: exhaust can build up quickly in any enclosed space, which is why outdoor placement is non-negotiable. Noise is the quality-of-life cost, and routine servicing of oil, filters, and fuel is the ongoing money pit.

Irish retailers are well aware of the mix. Carey Tools (Irish tools and equipment retailer) frames its generator range around backup power and site work — two very different use cases with very different expectations.

What appliances should not be used with a generator?

• Medical devices that need continuous, stable power
• Sensitive electronics without inverter-clean output
• Large motor loads that haven’t been added into your load calculation

The common culprit is start-up surge. Fridges, freezers, and water pumps draw extra current for the first second or two, and if the generator is already loaded near 80%, that surge pushes it over. Treat essential as a shortlist, not the whole house.

What is the downside of an inverter generator?

• Costs more than a conventional portable with similar output
• Produces cleaner power but less surge capacity
• Repairs may need specialist parts that standard dealers don’t stock

Inverter generators solve the power-quality problem with a price: they cost more than conventional portables, they produce cleaner power with less surge capacity, and repair often means sourcing specialised electronic parts. The full price comparison is in the dedicated section below.

The pattern: a generator is a trade-off. You trade fuel, noise, and attention for power during an outage — and the quality of that power depends on the type you choose.

Is it okay to leave a generator running all night?

It can be done safely, but the conditions are strict. The unit has to sit outside at least 20 feet from doors, windows, and eaves; a carbon monoxide detector has to be working inside; and someone has to be able to hear an engine sputtering over the rain. Leave a generator running overnight indoors or near an open window, and you’re gambling with the whole household.

Can you leave the house with a generator on?

• Never leave a running generator unattended indoors or near windows
• Keep it outdoors, at least 20 feet from doors and windows
• Turn it off and let it cool before refuelling
• Fit a CO detector in the living space

If you do leave the property, make sure someone who stays knows where the generator is, how to shut it down, and what the CO alarm sounds like. A portable petrol generator has no remote monitoring; once you’re gone, it’s running on trust. When in doubt, switch it off before you go.

Why this matters: the overnight test isn’t about the generator, it’s about the system around it — placement, detection, fuel, and someone paying attention at 3 a.m.

What is the downside of an inverter generator?

Inverter generators are the quiet, electronics-safe option — they produce cleaner, more stable power and run at lower noise levels than conventional units. The downsides are price, surge capacity, and repairability. At Clarke’s of Cavan (Cavan equipment retailer), the Victor LC2000I inverter costs €599.99 while a conventional Victor GG3300 3.7 KVA costs €499.99 — the €100 premium buys cleaner power and less noise, but also less headroom for motor starts.

• Price premium: clear at retail — roughly €100 more for the two comparable Victor units
• Power quality: clean enough for laptops, TVs, and routers
• Surge capacity: lower, so fridges and pumps start better on a larger model
• Repairability: specialist electronic parts, fewer local options

The trade-off: if you’re powering sensitive electronics in an outage, the inverter premium is money well spent. If you’re running power tools or keeping a freezer cold, a conventional unit gives more start-up kick for less cash.

Generator types and typical specs for sale in Ireland

Ten rows, one pattern: the more power quality you need, the more you pay per watt.

The pattern: the Irish market is not one market. Cheap portables compete on price, inverters compete on power quality, and diesel units compete on endurance. Buying channels range from equipment retailers like Atkins (Cork garden and site machinery retailer), which lists generators with free shipping over €80, to classifieds like DoneDeal for used units.

Buying a generator in Ireland: the upsides and downsides

A generator is a rescue tool, not an appliance — the pros only matter when the power is actually out, and the cons are with you every time you fill the tank. Weigh them honestly before you buy.

The implication: the upsides show up during outages; the downsides show up on every fill-up, every service, and every quiet evening. Count both before buying.

How to set up a generator for home backup

Setting up a home backup generator is a seven-step routine. Follow it once and you’ll know exactly what to do when the lights actually go.

1. List the essentials you want to power and add up their wattages.
2. Multiply that number by 1.25, so you stay safely inside the 80% rule.
3. Choose a generator whose rated output covers the adjusted total.
4. Position it outside, at least 20 feet from doors, windows, and eaves.
5. Fit a carbon monoxide detector in the living space and test it.
6. Run a heavy-duty outdoor extension cord to each appliance.
7. Turn the generator off and let it cool before refuelling.

The catch: the routine only works if every step is done before the outage. Sizing is a wallet decision; placement is the safety decision.

What’s confirmed, what’s still unclear

Some generator advice is settled; some depends on your particular house and habits. Here’s the line between confirmed and not-quite.

Confirmed facts

• Generators produce carbon monoxide — outdoor placement is essential (Carey Tools)
• The 80% rule is a standard safety guideline for sustained loads (Clarke’s of Cavan)
• Irish retailers stock petrol, diesel, inverter, portable, silent, and PTO generators (Dermot Casey Sales)
• DoneDeal carries thousands of live generator ads (DoneDeal)

What’s still unclear

• Exact sizing depends on individual appliance usage patterns — no number fits every house
• Applicability of the 20/20 rule varies with cable length, load, and conductor size
• Used-market condition varies so widely that a price check on the day matters more than any average

The pattern: most generator danger comes from setup mistakes, not bad machines; most sizing mistakes come from guessing instead of adding up loads.

What the market says

Irish dealers sell generators like they sell drills — short on spin, long on specs. The range descriptions below show what the market actually prioritises.

The Best Deals on Generators in Ireland.

— Mallow Tools, product page tagline

Diesel, petrol and inverter generators for backup power and site work in Ireland.

— Carey Tools, generator range description

From compact inverter models to diesel and PTO units.

— Dermot Casey Sales, generator range description

The takeaway: Irish retail positions generators as practical tools — backup for the home and muscle for the site. The marketing rarely mentions fuel burn or CO risk; that’s your job to supply.

For an Irish household, the choice is straightforward once the loads are listed: a 5–7 kW portable petrol or inverter unit covers the essentials within the 80% rule, while homes with pumps, outbuildings, or longer outage patterns should look at the diesel and silent-diesel classes. The used market can cut the upfront cost, but it shifts the risk to you — a private-sale generator that hasn’t been serviced is a gamble priced in euros and measured in power cuts. For anyone weighing that trade, the decision is clear: buy from a dealer who will stand over the warranty, or test a used unit hard before handing over cash.

Frequently asked questions