Open access allows a large consumer to buy electricity from a generator other than the local distribution company, paying the DisCom for use of the network rather than for the energy. For a charging operator with meaningful consumption at a single site, it can reduce energy cost materially — and the additional charges eat much of the apparent saving, so the arithmetic has to be done carefully.
Whether you qualify
Open access is available above a contracted demand threshold that varies by state, and green open access — for renewable sources specifically — generally carries a lower threshold than conventional open access. A single large DC site may reach it; a distributed network of small AC sites will not, because the threshold applies per connection rather than per company.
The charges that erode the saving
| Charge | What it is |
|---|---|
| Wheeling charge | Use of the distribution network |
| Transmission charge | Use of the transmission network, where applicable |
| Cross-subsidy surcharge | Compensates the DisCom for the subsidised consumers you leave behind |
| Additional surcharge | Levied where the DisCom has stranded contracted capacity |
| Banking and scheduling | Where generation and consumption do not align in time |
Cross-subsidy surcharge is usually the largest of these and the most variable between states. Several states waive or reduce it for renewable open access, which is frequently what makes the arrangement viable at all — so the comparison to run is not open access versus DisCom, but green open access versus DisCom.
The scheduling problem
Solar generates during the day. A charging site with an evening peak consumes when it does not. The mismatch is handled through banking arrangements whose terms vary considerably by state, and the banking terms often determine the whole economics. A generous banking arrangement makes solar open access attractive for a charging load; a restrictive one does not.
The simpler alternatives
Rooftop solar on the site, offsetting daytime consumption behind the meter, avoids most of these charges entirely and needs no open access approval. For a site with roof area and a daytime load — a mall, an office car park — it is usually the better first move, and it is a great deal less administrative work.