The heat is on — beyond what's displayed on your thermostat. During cold weather, scammers increasingly pose as utility company employees and other "energy savers" to try to get your money or valuables or sensitive information for identity theft.

Here's how:

The Shutoff Swindle

In the most common utility con, which happens every winter and during peak air-conditioning season, customers get phone calls warning that their service is about to be shut off because of unpaid bills.

Beware of utility company impostors or independent "energy auditors" that tend to appear unannounced at your front door. — Fresh Picked/Alamy

The callers claim to be billing representatives from your utility company but are actually crooks looking for a quick payoff. They tell you that to avoid an immediate shutoff, you need to settle an overdue bill by providing them with your credit card number or a prepaid debit card.

In recent weeks, utility customers from Connecticut to Hawaii have been targeted in this longtime scheme. But this winter, some utility impostors have been demanding payment for several months' worth of purported unpaid utility service, not just one, as had been the custom. They can be convincing. They may use "spoofing" software that lets them falsely display the name and phone number of your utility company on your Caller ID. But you should know that most utilities will mail at least one, if not several, past-due notices before terminating service. If you get a cancellation notification (especially by phone), always verify it by dialing the customer service number on your utility bill. Don't give any information to the caller.

The Supplier Switch

Have you been told you qualify for a 15 to 20 percent discount on your utility bill if you'll provide your customer account number? Before accepting the offer, know that the likely switch will simply take you to a different energy supplier. (After all, your current supplier already has your account number.)

In many states, customers can switch their electricity or natural gas suppliers. It's possible to compare rates and terms of state-vetted suppliers on the website of your state Public Utility Commission (PUC). But beware: Some suppliers employ telemarketers and door-to-door salesmen to recruit new customers with promises of lower rates for switching. But after a brief introductory period, rates may suddenly skyrocket — and you find yourself locked in a long-term contract with high cancellation fees. Attorney general offices in several states have sued energy suppliers for such bait-and-switch practices.

In some instances, you may be asked only for your name, address and utility account number — not a credit card. But with that information in hand, the new supplier can switch your power service provider, either with your blessing or by "slamming," the illegal practice of switching customers to another provider without their consent. Your best bet: If you're interested in switching energy suppliers, avoid unsolicited offers and instead compare your options at your state's PUC website.

Next page: Can I trust an unsolicited utility company worker? »