A lot of residential and commercial facilities use dual source meters (where they get separate register for the Grid Source and DG back up) to enable them to bill the consumers differential rates for Grid and DG.
There are older facilities which have been successfully operating single source meters successfully for similar operations except that they bill the consumers either on average rate (average of Grid and DG back up supply) or they calculate average consumptions for grid and DG out of total consumption and bill differential rates.
There are pros and cons for the dual source and single source meters.
Let us first look at the scenarios where dual source meters are more relevant:
- Partial DG backup – if the consumers have partial back up supply the Dual Source meter is used to control the connected load for Grid and DG scenarios.
- Historical acceptability of Dual Source Meters – If a facility or developer has historical practice of using dual source meters, it becomes a bit difficult to convince not to use dual source meters
- Demand Response Plasticity – if the consumers want to reduce their usage of DG electricity, the differential rates for DG rate trigger appropriate demand response. This is relevant only when some real time signal is available to the consumer whether DG is on or off.
In almost all other scenarios, there is no real requirement of dual source meters. With respect to the logic that a consumer should pay higher for DG, it should be remembered that the consumer does not really have a choice. The facility may consider DG back up as an additional supply option just like solar renewables. It is fair enough to bill the consumers on the average price Doesn’t your utility bill you on agreed regulated tariff. Do they charge the tariff based on their source of supply?