| How it delivers hot water |
Stores a set volume of heated water for use when needed. |
Heats water as it passes through the equipment. |
Uses a heat pump to transfer surrounding heat into a storage tank. |
| Sizing priority |
Tank capacity, first-hour delivery, recovery, fuel source, and peak household demand.
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Combined fixture flow, incoming water temperature, temperature rise, and available output.
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Tank capacity, household demand, recovery mode, installation temperature, and available airflow.
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| Space considerations |
Requires sufficient floor area, equipment clearances, drainage planning, and service access.
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Often wall-mounted but still requires utility access, clearances, venting when applicable, and service space.
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Requires tank floor space plus suitable air volume, intake and exhaust airflow, condensate drainage, and service access.
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| Utility considerations |
Gas or electric service, venting for applicable fuel-fired equipment, and compatible plumbing connections.
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Gas-line capacity or substantial electrical capacity may be required, depending on the system.
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Electrical supply, condensate disposal, surrounding temperature, airflow, and possible circuit updates.
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| Potential advantage |
Familiar operation, stored capacity, and often a straightforward option for a compatible replacement.
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Space-saving design and continuous operation while demand remains within the unit’s capacity.
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High-efficiency electric water heating when the installation location and household usage are suitable.
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| Important limitation |
The stored supply can be depleted, after which the system needs time to recover.
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Available flow is limited and supporting gas, electrical, or venting work may increase project scope.
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Recovery, noise, airflow, condensate, surrounding temperature, and installation volume require careful planning.
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