Electricity is used constantly but understood only vaguely by most people. Volts, amps, and watts appear on appliance labels and bills — here's what they mean in plain language.
Voltage (Volts)
Voltage is the electrical pressure driving current through a circuit — like water pressure in a pipe. UK mains voltage is 230V; US mains is 120V. Appliances designed for one standard can be damaged if used at the other without a converter.
Current (Amps)
Current is the flow of electrical charge, like flow rate in a pipe. The current an appliance draws depends on both voltage and the power it requires.
Current (A) = Power (W) ÷ Voltage (V)
UK ring main circuits: 32A breaker | Lighting circuits: 6A breaker
Power and Energy Costs
| Appliance | Typical Power | Cost per Hour (at 25p/kWh) |
|---|---|---|
| LED bulb | 10W | 0.25p |
| Laptop | 50W | 1.25p |
| Electric oven | 2,000W | 50p |
| Kettle | 3,000W | 75p (typically used briefly) |
| Electric shower | 8,500W | £2.13 |
Cost = Power (kW) × Hours used × Unit rate (£/kWh)
Circuit Protection
A fuse is a deliberately weak link that melts and breaks the circuit if current exceeds a safe level. Modern consumer units use circuit breakers instead, which trip automatically and can be reset. Residual current devices (RCDs) provide additional protection against electric shock by detecting current leaking to earth within milliseconds.
Safety Principles
Electrical work in the UK is regulated by Part P of the Building Regulations. Most electrical work beyond simple like-for-like replacement of sockets and switches must be carried out by a qualified, registered electrician and formally notified to the local authority. In the US, the National Electrical Code governs installations with broadly similar requirements for permits and inspection on new or altered circuits.
Always turn off the relevant circuit at the consumer unit before working on any wiring, and use a non-contact voltage tester to confirm a circuit is genuinely dead before touching any conductors — never simply assume a circuit is off because a switch appears to be in the off position, since switches can be miswired and multiple circuits frequently share the same physical space. These basic precautions are what separate routine electrical work from genuinely dangerous situations, and they apply regardless of how confident you feel about the task at hand.
Electrical work in the UK is regulated by Part P of the Building Regulations — most work beyond like-for-like replacement requires a qualified electrician. Always turn off the circuit at the consumer unit and use a non-contact voltage tester before touching any conductors.
Understanding Your Consumer Unit
The consumer unit, sometimes still called a fuse box even in modern installations that use circuit breakers, is the central point where mains electricity enters your home and is distributed to individual circuits. Each circuit — typically covering specific areas like upstairs sockets, downstairs lighting, or a dedicated high-power circuit for an electric shower or cooker — has its own breaker sized appropriately for the expected load and cable rating of that circuit.
Modern UK consumer units are required to include RCD (residual current device) protection on socket circuits, which detects tiny current leaks to earth — the kind that occur when a fault allows current to pass through a person — and disconnects the circuit within milliseconds, well before a dangerous shock can occur. If your home still has an older-style fuse box without RCD protection, upgrading to a modern consumer unit is one of the more important electrical safety investments available, regardless of how old or reliable the existing wiring otherwise appears to be.