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guidelines. Plug in the annual operating costs from the above exercise and calculate according to
the stated formula below. For comparative purposes, you can assume a 10-year heater life and
ignore maintenance factors. Maintenance is an issue, however, and one can expect to replace fossil
fuel heaters and heat pumps within 5-7 years. Roof mounted solar panel systems can require
moderate maintenance and have a design life exceeding 10 years. The SolarAttic solar pool heater is
relatively maintenance free with a design life of 20 years if pool chemistry is maintained.
Heat Pump heater