First, the bad news: SolarCity evaluated our house and determined that our big cottonwood tree casts too much shade onto the roof, so we are not good candidates for solar panels right now. I hope that over the next few years, solar technology will advance, becoming more efficient and less expensive. Smaller, better panels might fit on our roof and get enough sun to make them worth adding.
Now, the good news: our solar water heater has been working hard. The roof has reached at least 149, heating the water to the upper 120s during a sunny day. The solar controller disables the electric heater from 5am until 7pm. We try to shower and wash dishes in the morning or early afternoon so the solar heater can reheat the water. When the solar heater isn’t running, the water in the tank slowly cools, maybe a degree or two per hour. The hotter the water gets during the day, the longer it takes for the electric heater to kick in after 7pm, saving us more money.
The solar water heater helps in two ways. Most importantly, it heats the water after we use it. I think that’s where most of the savings occur. Second, it keeps the electric heater from running for 14 hours a day, whether to recharge after use or simply to maintain the desired temperature. I recently learned that you can buy a special timer for your traditional water heater to receive some of this second benefit. By letting the water cool when you don’t need hot water, such as during the day while you’re at work or at night while you’re sleeping, supposedly you can save anywhere from $2-20/month by adding a $40 timer.