The lights stay on. You barely notice.

How an automatic system works

1. The supply fails. An automatic transfer switch monitors your incoming supply continuously — not just for total loss, but for voltage outside acceptable limits.
2. The generator starts. After a short confirmation delay, so a momentary dip does not trigger a start.
3. The house transfers. Once the set is up to speed and stable, the switch moves your circuits from grid to generator. Usually 15 to 30 seconds from the outage.
4. The grid returns. The switch waits several minutes to confirm the supply is genuinely stable before transferring back.
5. The engine cools and stops. It runs on unloaded for a few minutes so it cools evenly, then shuts down and resets ready for next time.

Sizing: whole house, or the parts that matter

A typical UK home has a 60 to 100 amp supply, which is roughly 15 to 25 kVA. You can back up all of it, or you can be selective — and being selective is often the better buy.

Approach	What it means
Whole house	Everything works exactly as normal. Simple to live with, larger set, higher cost. Right where there is heavy load — a pool, workshop or several heat pumps.
Essential circuits	Heating, hot water, fridge and freezer, lighting, sockets, internet, alarm. A much smaller set, and honestly enough for most households.
Load managed	A modest set with controls that shed the heavy items when needed. More electronics, but it gets close to whole-house behaviour on a smaller engine.

Our usual residential range runs from around 10 kVA up. Below that you are into portable territory, which is a different thing entirely — and worth being clear about: a portable set with an extension lead is not a standby system and will not run your heating.

With renewables, if you have them

If you already have solar and battery storage, or are considering it, the two work together well.

• The battery covers the first few hours silently. Most outages end before the generator ever needs to start.
• The generator handles the long ones, and recharges the battery while it runs.
• The rest of the year the battery earns its keep on tariff arbitrage and solar storage, which a standby generator never does.

Where the whole system is being designed together, that combination usually gives a smaller engine, far fewer starts, and something useful 365 days a year rather than kit that sits waiting.

Fuel

Three practical options for a home. There is more detail on fuel options.

• Diesel — the most common. Needs a tank, and fuel degrades if it sits for years, so it needs managing.
• LPG — bulk tank or cylinders. Stores indefinitely without degrading, which suits equipment that might sit unused for a year.
• Natural gas — where a mains gas supply exists, no storage at all and no refuelling. The catch is that it relies on a supply which may itself be affected in a major incident.

What a proper installation includes

• Load assessment and sizing against your actual consumption
• Base, mechanical installation, and fuel system
• Automatic transfer switch with protection against under and over voltage
• Dedicated earthing arrangement — an earth rod, permanently installed
• Overload and earth fault protection on the supply cabling
• Testing and certification to BS 7671
• Building control notification under Part P, which we handle
• Commissioning under load, and a handover that shows you how it behaves