Some water heaters use waste heat or water as a heat source, and some water heaters perform air conditioning or dehumidification as their primary function and water heating as their byproduct. One manufacturer sells only components, i.e. a tank and heat exchanger that can be plumbed into a refrigeration system ahead of the condenser section. Another manufacturer sells an indoor pool heater variation that heats the pool while performing ambient air dehumidification as a byproduct. Others provide wastewater heat recovery to heat potable water . HPWHs can work any time there is a need for hot water heating and a cooling load or opportunity.
Performance varies with the situation.
An economic comparative analysis must be benchmarked against some alternative arrangement. Energy performance is fairly straightforward. This means they produce about twice as much hot water per kWh as electric resistance water heaters. Maintenance costs are greater than simple resistance water heating. The maintenance requirements and cost are more similar to that of conventional air conditioning equipment of similar tonnage.