Inverter
Electrical Energy stored in a battery or from a PV Solar array is Direct Current (DC) that is at a fixed level of voltage. One battery is typically 12 V DC. The mains electricity used in houses and offices is Alternating Current, that is the voltage level swings up and down in the shape a sinusoidal wave (Remember sin() from school maths?). So an Inverter takes a DC voltage and converts it to AC, normally at a much higher voltage (230V AC). They are rated on the power they can handle, that is the current they can produce in the from of kVA (Thousand Volt Amps) since Power is a product of Voltage multiplied by Current (although kVA is apparent power not real power, but that’s a story for another day).