Transformer capacity: why KSEB sometimes says wait, and what you can do about it

Most people think the decision to install solar is the hard part. In more and more of Kerala, the first real question is a different one: does the transformer that feeds your house have room for another solar system? If it does not, the best-designed plan in the world waits.

Why a transformer has a solar limit

Your local distribution transformer was built to carry power one way, from KSEB to the houses around it. Rooftop solar reverses that at midday: every system on the transformer exports its surplus at the same time, and the transformer and the low-voltage lines have to carry it the other way. Too much reverse flow pushes up the voltage on the line and loads the transformer beyond what it was planned for. So KSEB caps how much rooftop solar each transformer can take, and checks the remaining room before it approves a new system.

Where the check happens

This is what the feasibility fee pays for. When you apply, KSEB looks at the transformer you are fed from, how much solar is already connected to it, and whether your connection and line can carry your export. If there is room, feasibility is approved. If the transformer is full, it is not, and the fee is not refunded.

KSEB also publishes the loading of each transformer on its portal, and your bill shows which transformer you are fed from. Look yours up, or ask us to, before you pay for feasibility on a transformer that is already full.

Why waiting a month can cost months

Solar installations in Kerala are growing quickly, and capacity on a transformer is taken in the order applications are approved. A neighbour who applies before you can use up the room you were counting on. That is the point of our short video on this: the plan that is put off for a month can find the transformer full when it comes back. The subsidy works the same way, by the guidelines in force when you apply. If you have decided, register early.

If the transformer is full

First, ask about timing: KSEB does augment transformers over time, and the section office can tell you whether work is planned for yours. Second, look at size: a smaller system may still fit where a larger one does not. Third, look at how the system is configured: a system that does not export, or a battery system that uses its own power in the house, places less load on the transformer, and your installer should talk you through what KSEB will accept for your connection.

What you should not do is install first and apply later. Nothing goes on the roof before KSEB's approval: installing early can cost you the subsidy, and it does not make the transformer any bigger.