Energy IndependenceSolar Heating
Building a Drain-Back Solar Hot Water Loop for Freezing Climates
Drain-Back Solar Hot Water for Cold Climates: Full Build
14 minAdvanced
Renewable Energy
The Free Hot Water Retrofit
Two evacuated tube collectors, an 80-gallon exchange tank and the drain-back controls for freezing climates.
What you get out of it
Your water heater stops being the second-biggest line on the bill — most homes cut 60–70% of that load.
This is for you if…
- You have a south-facing roof or wall
- You want a fast payback, not a 20-year one
- Your current tank is electric or propane
What you get
- Evacuated tube collector array$1,480 value
- Differential controller and sensors$340 value
- Pump station and expansion tank$520 value
- Insulated line set and fittings$290 value
- Tie-in diagram for your existing tank$240 value
- Freeze protection setup guide$160 value
Total value$3,030
Your price$3,260
Itemized, so you can check our math
- 2 × 30-tube evacuated collectors
- 80 gal dual-coil exchange tank
- Drain-back reservoir and pump station
- Differential controller and sensors
- Mounting rails and roof flashing
Specifications
- Collector area: 54 sq ft
- Tank: 80 gal, dual coil
- Freeze strategy: drain-back, no glycol
- Pump: 20W DC
Why it's specified this way
A closed-loop drain-back setup that survives a −12°F morning without glycol. It carries roughly 70% of our household hot water load across the year and takes a full winter afternoon to install.
"The sizing worksheet told me I needed half the array the installer quoted. I built it myself over two weekends and my last twelve bills total $214."
Dana Whitfield
Boone, North Carolina
4,180 kWh produced · $2,340 saved in year one
$3,260
4.71 ★ from 18 reviews · In stock
Bill-Drop Guarantee — if it doesn't work the way this page says, tell us within 365 days and you get your money back. You keep the guides.
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