‘Net metering’ is sometimes seen in the news in the context of promoting the

The correct answer is: production and use of solar energy by the households/consumers.

To understand why, let us break down the concept of Net Metering thoroughly, step by step.

What is Net Metering?
Net metering is a billing and energy policy mechanism that allows individual electricity consumers — typically households or small businesses — who generate their own electricity (most commonly through rooftop solar panels) to feed the surplus electricity they do not consume back into the main electricity grid. In return, they receive a credit on their electricity bill for that surplus energy.

How Does It Work? — Step-by-Step:

Step 1 — Solar Installation:
A household installs rooftop solar panels. During the day, these panels convert sunlight into electricity (DC), which is then converted to AC power via an inverter for home use.

Step 2 — Consumption vs. Generation:
If the solar panels generate more electricity than the household is currently consuming, that excess power does not go to waste.

Step 3 — Feeding Back to the Grid:
The excess electricity is automatically fed back into the local electricity distribution grid. A special bidirectional meter (the "net meter") records both:
- The electricity drawn from the grid (when solar generation is insufficient, e.g., at night), and
- The electricity fed into the grid (surplus solar energy).

Step 4 — Net Calculation and Billing:
At the end of a billing cycle, the electricity board calculates the net difference:

$\text{Net Units Consumed}=\text{Units Drawn from Grid}-\text{Units Exported to Grid}$
The consumer is billed only for this net amount. If the exported units exceed the drawn units in a period, the consumer earns a credit that carries forward to the next billing cycle.

Why is this specifically linked to Solar Energy for Households?
Net metering is a demand-side management and renewable energy promotion tool. Governments and electricity regulators introduce net metering policies specifically to:
- Encourage households to invest in rooftop solar panels.
- Reduce the financial payback period for solar installation costs, making it economically attractive.
- Promote decentralized, clean electricity generation.
- Reduce dependence on fossil-fuel-based grid electricity and lower carbon emissions.

In India, for instance, the Ministry of New and Renewable Energy (MNRE) and state electricity regulatory commissions have introduced Net Metering Regulations under frameworks like the Grid Connected Rooftop Solar Programme to boost household-level solar adoption. This is why the term frequently appears in news related to solar energy policies.

Why the Other Options Are Incorrect:
- Piped Natural Gas (PNG): PNG is distributed through pipelines and billed based on volumetric consumption. It has no bidirectional flow or grid-export concept, so net metering does not apply.
- CNG kits in motor cars: CNG (Compressed Natural Gas) is a vehicular fuel. It involves refueling at stations and is entirely unrelated to electricity metering or grid interaction.
- Water meters in urban households: Water metering tracks water consumption only; there is no mechanism to feed water back into a supply network and earn credits, so the concept of net metering does not apply here.

Conclusion:
The term "Net Metering" is exclusively and directly associated with the production and use of solar energy by households/consumers. It is the key policy instrument that makes rooftop solar panels financially viable for ordinary consumers by ensuring they are fairly compensated for the clean energy they contribute back to the grid. This is precisely why the first option is the correct answer.