Building a solar water heater isn’t exactly for beginners. It requires installing pipes, glass and, preferably, insulation. But for a do-it-yourself type, it’s ideal money- and planet-saving project. You can build a batch water heater for less than $100.
A batch heater is also called an integral passive solar water heater — “integral” because the solar collector and storage tank are combined. It’s the simplest system to build at home, and it really only requires a few basic parts. (This is just a brief overview; for complete instructions, see DIY sidebar.)
- Electric water heater tank (used is fine, as long as it’s in good shape)
- Black paint
- Plywood box (large enough to hold the tank)
- Sheets of glass
- Hinged lid for the box (to reduce nighttime cooling)
- Insulation material
- Mountings (for roof, side of house, or ground level)
Construction is pretty straightforward:
- Paint the water tank black.
- Secure glass to the top of the box.
- Insulate the box and the additional lid and cut holes in the box for inflow and outflow pipes.
- Secure the water tank inside the box.
- Route incoming cold water into the bottom of the tank, and outgoing hot water from the top of the tank to the home’s water-heater tank
- Mount unit in desired location (roof is usually best for sun-exposure).
While building the water heater may be pretty easy, there are other factors to consider. You have to determine the prime location for heater so it’s exposed to the most sunlight per day, which can take some calculating. You also need to make sure the ideal location can support the weight of the setup. And as with any other water heater, you need to figure out what size tank you need so you don’t end up running out of hot water in the middle of your shower — and determine how much glazing surface area you need to heat that water volume.
If you’re not comfortable making these determinations, you might want to shell out the cash for a professionally built setup.
Either way, there are some general pros and cons associated with solar water heaters. We’ll start with the upside.