Solar thermal rooftop arrays provide hot water (funded by a grant from the Massachusetts Technology Collaborative with matching funds from Tufts). The vertical axis of the graph shows the BTUs that where consumed to heat the domestic hot water (showers, dishwashers, laundry, etc.) The sum of the gas heated (blue) and solar heated (light green) water gives the total BTUs consumed for hot water. The dark green portion of the solar heated water is either used later or heat that is lost during storage.

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