Shore power calculator
Check whether your appliances fit within your marina shore power supply.
Related tools
Appliances
Worked example
A boat on a 16A shore supply running the following simultaneously:
| Appliance | Wattage | Current at 230V |
|---|---|---|
| Battery charger | 1,200 W | 5.2 A |
| Air conditioning | 800 W | 3.5 A |
| Kettle | 2,000 W | 8.7 A |
| Total | 4,000 W | 17.4 A |
Result: overloaded — 17.4A exceeds the 16A supply. Don't run the kettle while the AC and charger are running.
How it works
Current (amps) = Power (watts) ÷ Voltage. On a 230V supply, a 2,000W kettle draws 8.7A. Add up all appliances running simultaneously and compare to your supply rating.
Current (A) = Total watts ÷ Supply voltage
UK marinas typically provide 16A single-phase supplies. Some provide 32A. Stay below 80% of the rated supply to avoid tripping the breaker under inrush currents.
Common appliance wattages
| Appliance | Typical wattage |
|---|---|
| Battery charger (smart, 30–40A output) | 400–1,500 W |
| Air conditioning (small marine unit) | 600–1,200 W |
| Electric kettle | 1,500–2,200 W |
| Microwave | 700–1,200 W |
| Electric hob (single ring) | 1,000–2,000 W |
| Laptop charger | 45–100 W |
| TV / monitor | 30–150 W |
| Dehumidifier | 200–500 W |
Frequently asked questions
What does a standard UK marina shore power supply provide?
Most UK marinas provide a 16A single-phase 230V supply via a blue CEE socket on the pontoon. That's a maximum of 3,680W (16A × 230V). Some berths have 32A supplies (7,360W). Large commercial berths may have 63A three-phase — check with the marina before connecting high-draw appliances.
Why does my breaker trip even when I'm under the rated amps?
Inrush current — the brief surge when a motor or compressor starts — can be 3–6× running current. An air conditioner drawing 3.5A running may spike to 15A for a fraction of a second on startup. If you're already near the breaker limit, that spike trips it. Stagger the startup of high-draw appliances.
Can I run a kettle and a battery charger at the same time on 16A?
Probably not both at full load. A 2,000W kettle (8.7A) plus a 1,200W charger (5.2A) = 13.9A — within the 16A limit, but add any other loads and you'll trip. Turn off the charger while the kettle boils, then switch back.