Rooftop Solar Net Metering

Net metering allows a rooftop solar consumer to offset electricity taken from the distribution grid against surplus solar electricity supplied to it. It accounts for grid imports and exports in kilowatt-hours (kWh) and uses their difference to determine the net energy balance for billing under the applicable regulations.

How electricity flows are measured

A grid-connected rooftop solar system supplies the premises while remaining connected to the distribution network. A bidirectional meter records electricity drawn from the grid and electricity supplied to it separately.

• When solar generation is below the premises' electricity requirement, the shortfall is met through grid imports.
• When solar generation exceeds the requirement, the surplus flows into the grid and is recorded as an export.
• Solar electricity consumed directly within the premises is self-consumption: it reduces grid purchases but is not itself recorded as an export.

How the net balance becomes a bill

For the applicable accounting period, net electricity consumption equals grid imports minus grid exports. Net metering therefore offsets electricity quantities before the relevant billing rules are applied.

• If the meter records imports of 300 kWh and exports of 180 kWh, the net imported energy is 120 kWh.
• Exports are not the same as total solar generation: electricity used directly by the household or establishment never enters the grid.
• If exports exceed imports, the consumer has a surplus energy balance. Its carry-forward, adjustment or payment depends on the applicable State Electricity Regulatory Commission regulations and settlement arrangements.
• A zero net energy balance does not necessarily mean a zero bill, because fixed charges and other applicable charges may remain payable.

How net metering differs from other arrangements

The key distinction is whether imported and exported electricity are offset as energy units or valued separately in money.

• Under net billing, imports and exports are valued separately at their applicable tariffs, and the export credit is adjusted against the consumer's bill.
• Under gross metering, the entire solar generation is supplied to the grid and paid for separately, while the consumer's electricity purchases are billed independently.
• Net metering can reduce purchased electricity and encourage rooftop solar adoption, but the financial benefit depends on consumption patterns, applicable tariffs and settlement rules.