There are gas boilers that are installed in buildings that have a back-up system (either oil or electric) which allow you to pay a lower rate than general service. These are classed as interruptible with your local utility (IS or ISS). These interruptions often take place when the temperatures drop to single digits and the demand on the gas delivery system is at its highest. Your company will receive 24-48 hours notice and are required to drop their gas usage to zero for a specific time period. The confusion comes when you have contracted with a supplier and you think that you can use that contracted gas. This is actually cut off and you must either switch to your back up system or you run the risk of paying spot pricing and incurring numerous penalties. When you purchase new assets, always make sure that you check your service class and don’t let anyone remove your backup system. It is extremely expensive to remove your community from interruptible rate class and often is cheaper to fix or install a new back up system.