Solar Water Heating Savings Calculator
Estimate annual backup-energy savings and simple payback for solar water heating from daily hot-water use, temperature rise, solar contribution and energy price.
Default project preview
$417.52
Daily hot-water thermal demand
9.53 kWh
Annual hot-water thermal demand
3,479 kWh
Solar thermal contribution
2,088 kWh
Monthly average savings
$34.79
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Daily hot-water volume
Enter this project assumption in gal/day. The current imperial default is 60 gal/day.
Incoming cold-water temperature
Enter this project assumption in °F. The current imperial default is 55 °F.
Delivered hot-water temperature
Enter this project assumption in °F. The current imperial default is 120 °F.
Annual solar contribution
Enter this project assumption in %. The current imperial default is 60 %. Minimum: 0. Maximum: 100.
Backup-heater efficiency or COP
Enter this project assumption in a unitless value. The current imperial default is 0.9. Minimum: 0.1.
Backup energy price
Enter this project assumption in per kWh. The current imperial default is 0.18 per kWh. Minimum: 0.
Operating days per year
Enter this project assumption in days. The current imperial default is 365 days. Minimum: 1. Maximum: 366.
Net installed system cost
Enter this project assumption in a unitless value. The current imperial default is 7000. Minimum: 0.
How to read the outputs
Daily hot-water thermal demand
water heating only. Default preview: 9.53 kWh.
Annual hot-water thermal demand
365 operating days. Default preview: 3,479 kWh.
Solar thermal contribution
60% solar fraction. Default preview: 2,088 kWh.
Monthly average savings
annual savings divided by twelve. Default preview: $34.79.
Simple payback
net system cost ÷ annual savings. Default preview: 16.8 years.
Ten-year gross savings
before maintenance and degradation. Default preview: $4,175.20.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Water-heating energy depends on daily water mass × temperature rise. Solar thermal contribution = annual demand × solar fraction. Avoided backup input = solar contribution ÷ backup efficiency.
FAQ
Solar Water Heating Savings Calculator questions
What is solar fraction?+
It is the share of annual hot-water thermal demand supplied by the solar system rather than the backup heater.
Why can backup efficiency be greater than one?+
A heat-pump water heater may be represented by a coefficient of performance greater than one instead of a resistance or fuel efficiency below one.
Is simple payback a full financial analysis?+
No. It excludes financing, maintenance, incentives, energy-price changes and equipment replacement.