One way of cutting your energy bills is to use a "bill auditing service" to find advantageous errors in them. While most utility bills are correct, a small percentage of them are not. Finding such errors is now a billion-dollar business.
Some contracts include other clauses that go beyond simple refunds. A common condition is that payments for such overcharges continue at the 50-50 rate for three to five years. The logic is simple: If the bill auditor had never found the mistake, you would have been paying extra forever, so sharing the rate reduction for a few years is a small price to pay. In other cases, some bill auditors try to lay claim to savings (or rate reductions) found instead by their customers. Few imagine such difficulties could arise when signing a one-page contract that involves no cash outlay.