The Brief: Modest, Clear, And Refreshingly Specific
A couple in Banffshire wanted a straightforward answer to power cuts. Keep the lights on, keep the heating running. No large budget, and no complexity they hadn't asked for.
That's a genuinely useful brief, and it's more common than the industry likes to admit. Not everybody wants whole-house resilience with automatic load management and an app. Plenty of people want the essentials to keep working when the weather takes the power out, at a price that makes sense against how often that actually happens.
North Scotland gives that question a sharper edge. Power cuts here tend to arrive with the weather, at night, in winter — which is precisely when losing heating stops being an inconvenience and starts being a real problem.
Sizing To The Brief, Not To The Invoice
We supplied and installed a Hyundai 8kVA long-run diesel generator, sized to exactly what they asked for rather than oversold on capacity they didn't need.
It's worth being blunt about why that matters, because oversizing is the easiest thing in the world to sell. A bigger number sounds safer. The customer rarely has the information to push back. And the cost of getting it wrong doesn't show up until later.
Oversizing charges you twice. Once on the invoice, and then again for the life of the set — in fuel, and in prolonged light-load running, which isn't good for a diesel engine. A generator loafing at a fraction of its capacity is not a well-specified generator.
The honest question isn't how big the house is. It's what genuinely needs to run while the mains is off. Lights, heating and its controls, fridges and freezers, some sockets — that's a modest load, and 8kVA covers it comfortably. The number only climbs if you insist on running electric showers or an electric hob at the same time, which nobody needs to do during a power cut.
The "long-run" part matters too. An enlarged fuel tank means the set runs for many hours without refuelling — which is the point when the cut is weather-related and might outlast a standard tank. Going out to refuel a generator at 3am in a Banffshire gale is exactly the situation you're trying to design out.
The Automatic Transfer Switch: The Part That Makes It Work
The generator was paired with an automatic transfer switch. The moment the power goes, the set starts itself and takes the load — no need to go outside and physically start it, whatever the weather or the time of night.
This is usually the difference between a generator that gets used and one that doesn't. A manual set demands that someone is home, awake, willing to go out in the dark and rain, and confident about the starting procedure. Every one of those conditions is a point of failure, and they all tend to fail at once — at 2am, in bad weather, which is when the power actually goes.
- Mains failure detected automatically, with no one needing to be present
- Generator starts and picks up the load on its own
- Works identically whether the house is occupied or empty
- Transfers back and shuts down when the mains returns
The Outcome
The couple have reliable backup power that looks after itself. Lights and heating stay on through a power cut, and they don't have to do anything to make that happen.
The part they hadn't fully anticipated is what it does while they're away. Their fridges and freezers keep running through a cut with nobody at home — which, for anyone who has come back from a fortnight away to a defrosted freezer and a ruined floor, is worth a great deal on its own.
Right-sized beats impressive. The best generator installation isn't the biggest one we can justify — it's the one that does what you asked, costs what it should, and starts on its own at three in the morning without anybody thinking about it.
Common questions
What size generator do I need to keep a house running in a power cut?
Far less than most people assume, if you're honest about what actually needs to run. Lights, heating controls, a boiler, fridges and freezers and some sockets is a modest load — something around 8kVA covers it comfortably for a typical home. The figure only climbs if you insist on running electric showers, immersion heaters or an electric hob at the same time. The right question isn't how big your house is, but what you genuinely need working while the mains is off.
What is an automatic transfer switch, and do I need one?
An automatic transfer switch detects that the mains has failed, starts the generator and transfers the load across to it without anyone doing anything. Without one, someone has to go outside and start the set by hand. For a holiday home, a rural property, or anyone who wants their freezers protected while they're away, an ATS is usually the part that makes the whole installation worth having.
What does "long-run" mean on a diesel generator?
A long-run set has an enlarged fuel tank, so it can run for many hours without being refuelled. That matters in rural Scotland, where a weather-related power cut can last well beyond a standard tank — and where going out to refuel in the middle of the night in bad weather is exactly what you're trying to avoid.
Will you recommend a smaller generator if that's all I need?
Yes. Oversizing is easy to sell and costs the customer twice — once in the purchase, and again in fuel and poor light-load running for the life of the set. We size against what you actually want to keep running, tell you plainly what that needs, and leave sensible headroom rather than padding the specification.