Electrical conversions answer a different question from energy conversions: not how much energy exists, but at what rate it flows and what infrastructure that requires. Power is measured in watts, current in amperes, potential in volts, and battery capacity in amp-hours or milliamp-hours. The critical point — and the reason careless converters mislead people — is that several of these conversions are not fixed unit pairs. Watts and amps are related through voltage by Ohm's power law (P = V × I), so the same 3,000 W appliance draws 13 A on a 230 V European circuit and 25 A on a 120 V North American one. Milliamp-hours measure electric charge, not energy, so a capacity rating means nothing until multiplied by cell voltage. Every converter in this category that depends on voltage asks you to supply it rather than hiding a single assumption behind the answer. This is also the category that decides real installation questions: which breaker, which cable, whether a home EV charger needs a 32 A circuit, and how large a battery bank must be at 12 V, 24 V or 48 V.

When to Use Electrical & Power Conversions

Checking whether an appliance fits an existing circuit: cables and breakers are rated in amps while appliances are labelled in watts.
Planning an EV charger installation, where a 7.4 kW charger requires 32 A at 230 V and therefore dedicated cable and protection.
Comparing two batteries honestly by converting mAh or Ah ratings into watt-hours at their actual voltage.
Checking airline lithium battery compliance, which is regulated in watt-hours (100 Wh carry-on, 160 Wh with approval) rather than mAh.
Specifying motors and drivetrains across markets, where electric power is quoted in kilowatts and combustion output in horsepower or PS.
Sizing off-grid, marine or campervan systems where the choice between 12 V, 24 V and 48 V changes the amp-hours needed for the same stored energy.

Common Electrical & Power Conversion Mistakes

1Converting watts to amps without stating the voltage. The result changes by a factor of two between 120 V and 230 V supplies.
2Ignoring power factor for inductive AC loads. A 2 kW motor at 0.85 power factor draws about 10.2 A at 230 V, not 8.7 A.
3Comparing milliamp-hour ratings across different voltages. A 10,000 mAh 3.7 V pack holds 37 Wh; the same rating at 12 V holds 120 Wh.
4Loading a breaker to its exact rating. Continuous loads should stay below 80% of the rating, so a 16 A circuit supports about 2,900 W sustained.
5Planning battery banks around nameplate capacity. Lead-acid should not be discharged below 50%, and inverters lose a further 10–15%.
6Treating horsepower and metric PS as identical — they differ by 1.4% (745.7 W versus 735.5 W).

Practical Electrical & Power Examples

A 7.4 kW home EV charger draws 32 A at 230 V, which is why 32 A is the standard dedicated circuit for single-phase home charging.

A 26,800 mAh power bank at 3.7 V holds 99.2 Wh — deliberately just under the 100 Wh airline carry-on threshold.

A 100 Ah leisure battery stores 1.2 kWh at 12 V, of which only about 600 Wh is safely usable if it is lead-acid.

A 150 hp petrol engine and a 110 kW electric motor have essentially the same nameplate power output.

Most Used Electrical & Power Converters

Watts → Amps Amps → Watts Milliamp-hours → Watt-hours Amp-hours → Watt-hours Kilowatts → Horsepower Watts → BTU per hour