> ## Documentation Index
> Fetch the complete documentation index at: https://docs.voltview.co.uk/llms.txt
> Use this file to discover all available pages before exploring further.

# Energy and power

> kWh, kW, kVA, kvarh, and the multiplier that turns a register into a billed quantity.

Commercial electricity is not one number. The meter (and the bill) can report **active**, **reactive**, and **apparent** energy. VoltView stores all three when the supplier or the invoice provides them.

## The three quantities

| Quantity          | Everyday meaning                                                           | Instantaneous unit | Energy unit | VoltView fields                                                  |
| ----------------- | -------------------------------------------------------------------------- | ------------------ | ----------- | ---------------------------------------------------------------- |
| **Active (real)** | What the load actually consumes as useful work and heat                    | kW                 | **kWh**     | `consumptionkWh`, `activeImportKwh`, `activeExportKwh`           |
| **Reactive**      | The out-of-phase component from motors, transformers, and some electronics | kvar               | **kvarh**   | `consumptionKvarh`, `reactiveImportKvarh`, `reactiveExportKvarh` |
| **Apparent**      | What the network has to make available                                     | kVA                | **kVAh**    | `consumptionKvah`, `apparentKvah`                                |

On a clean sine wave they form a right triangle:

```
kVAh²  =  kWh²  +  kvarh²
kVA²   =  kW²   +  kvar²
```

**Power factor** is active ÷ apparent (kW / kVA, or kWh / kVAh over the same interval). A site that draws 80 kW and 100 kVA is at 0.8 PF.

<Note>
  Reactive energy has a cycle-average of zero — it is not "used up" the way kWh is. The network still has to carry the extra current, so suppliers charge for it when power factor is poor, and they size **capacity** in kVA rather than kW. See [Demand and capacity](/metering/demand).
</Note>

Export uses the same units. A solar site can have `activeExportKwh` on the export MPAN. Reactive import/export are electricity-only; they do not apply to gas.

## What you see on a bill

A typical C\&I invoice line-up:

| Charge          | Based on                                         | Rate you will see |
| --------------- | ------------------------------------------------ | ----------------- |
| Unit charge     | Active kWh (sometimes split day / night / peak)  | p/kWh             |
| Standing charge | Days in the period                               | p/day             |
| Capacity charge | Contracted [MIC](/metering/demand#billing-terms) | p/kVA/day         |
| Reactive charge | kvarh above a power-factor threshold             | p/kvarh           |

Day and night kWh are still active energy. They are the same kWh split across [registers](/metering/overview#how-it-sits-in-voltview), not a different physical quantity.

If the invoice kWh and the half-hourly sum disagree, check the [billing multiplier](#billing-multiplier) and the read types (actual vs estimated) before assuming the meter is wrong.

## How modern meters get kWh and kvarh

The meter samples voltage and current, multiplies them, and integrates:

* Instantaneous `v × i`, averaged over a cycle, is **active** power.
* Apparent power is `Vrms × Irms`.
* Reactive power is the remaining leg of the triangle on a sine wave. Meters use several practical methods (a 90° shift of one waveform, a filter, or the triangle itself). They diverge once the waveform is distorted.

VoltView does **not** recompute kvarh from kWh. We take the meter or the invoice value. If only kWh is present, we do not invent a power factor.

## Billing multiplier

On a whole-current meter the face reading *is* kWh. On a CT-metered supply the instrument sees a stepped-down current (usually 5 A). HV sites also step voltage down through a VT (PT). The true primary quantities are much larger.

```
Billing multiplier  =  CT ratio  ×  VT (PT) ratio  ×  meter multiplier
```

Leave the VT term at **1** on a 400 V CT-metered board — the meter still sees line voltage.

| Site                                         | Ratios       | Billing multiplier |
| -------------------------------------------- | ------------ | ------------------ |
| LV, 400/5 CTs, no VT, meter ×1               | 80 × 1 × 1   | **80**             |
| HV, 11 kV / 110 V VT and 200/5 CTs, meter ×1 | 40 × 100 × 1 | **4,000**          |

Billed kWh for the period is:

```
(current index − previous index)  ×  billing multiplier
```

The multiplier is printed on the meter face when it is not 1, and it is almost always printed again on the invoice. Four-dial meters may also be ×10, or may record only a fraction of true kWh.

<Warning>
  A register read in VoltView is the **index**, not the billed energy. If you compare `currentMeterReading − previousMeterReading` to `consumptionkWh` and they differ by a round factor (10, 20, 40, 80, 200, 400…), you are looking at an unapplied CT/VT multiplier, not a parse error.
</Warning>

## What we do not do

* Infer kvarh or kVAh from kWh and a guessed power factor.
* Apply a silent multiplier to a smart-meter interval series. HH settlement data is already in true kWh.
* Treat inverter kWh as a substitute for the settlement meter. Generation is mapped next to the MPAN; it does not replace it. See [Solar](/assets/solar).