Many governments are, in general, trying to encourage citizens to produce their own solar energy to reduce reliance on fossil fuel. But households cannot rely entirely on their solar production alone.
While they may produce more than their need of power during the day, during the night, and in bad weather, they will have to rely on the grid. Storage is costly, at least initially. The best option is to have a grid-connected system which can feed to the grid and receive from it.
Different tariff and incentive schemes are in vogue, and accordingly, different metering systems are used.
Net metering is one such system. In this system, a bidirectional meter-one which can count forward and backward-is used. The consumer pays for the ‘net’ energy used by him / her. In case the consumer supplies more energy than he uses, he is given credit for it at specified rates under specified terms.
Another system is dual metering. Two separate unidirectional meters are used per consumer. All produced energy, or only surplus, may be supplied to the grid.
One meter records the total energy received from the grid, and the other records that fed in to the grid. This type of metering is useful when different rates apply to energy provided by grid and that by the consumer.
The rate at which the utility buys energy from the consumer producer is called the feed-in tariff (FIT). Feed-in-tariff was very attractive in Australia a few years back, but not so now. Current feed-in-tariff rates are about one third of the retail rate.
This means the consumer is encouraged to produce just about what he needs and not more. Also the term feed-in tariff has now been replaced by the term ‘buyback’. In USA feed-in tariff is used in some states, but the rates may differ from state to state.
Summary of metering schemes: net metering only requires one meter. A feed-in-tariff requires two. Time-of-use (TOU) requires a smart meter.