Pros and cons of indirect water heaters. There are a couple if you have a heating system. A water heater itself, a stand-alone water heater burns at 62 percent efficiency. Heating systems have a higher efficiency upwards of 94 percent, and on the low side of 82 to 84 percent. So, automatically, just by having an indirect water heater, you're going to gain a 20 percent greater efficiency by not having a stand-alone water heating tank. The indirect water heater is a lot more capable to deliver more hot water when you need it. So, the indirect is faster in recovery, has a much better efficiency rating and lasts a lot longer as well because there's no flame underneath and no expansion to speak of, so we get a longer life out of an indirect water heater.