Solar water heaters are theoretically an investment, using no money.
It's practically impossible. The reason is that every year, there is cloudy rain and snow and less sunny weather in winter. In this climate mainly by electric heating hot water (there are some products are heated by gas), an average of more than 25%~50% of hot water per year need to rely entirely on electric heating (different between regions, cloudy areas of the actual power consumption is also greater. Statistics from the Shanghai region for nearly three years show that the average annual rainy day is as high as 67%, the use of solar water heaters at full capacity of 70% of its thermal energy from electricity or gas). In this way, the actual power consumption of solar water heater heat pump water heater large. In addition, the "Electrothermal antifreeze belt (only in the northern region)" laid on the outdoor pipe path of the solar water heater also consumes a lot of electricity.
In addition, solar water heaters in the structure there are a variety of difficult to solve the technical defects. 1. Hot water pipes up to more than 10 meters long, every use to waste a lot of water. In typical φ12 mm pipes, 0.113 kg of water is stored per 1 meters in length. If the average length of a solar hot water pipe is 15 meters, about 1.7 kilograms of water will be wasted per use. If used on average 6 times a day, 10.2 kilograms of water are wasted per day; 360 kg of water is wasted per month; 4320 kg of water is wasted each year; and 43200 kg of water is wasted in ten years! Saving some electricity at the cost of wasting water, I'm afraid neither the government nor the people will recognize it if they know it.
More than half of China's more than 660 cities are short of water at different levels, of which 111 are severely short of water, and the annual impact of water scarcity on industrial output reaches more than 200 billion yuan. 2. It takes a whole day of sunshine to get the water hot, and when the weather is good, there is only a guarantee of hot water at night, and very little hot water is available during the day and at night.
There is no guarantee that the user will have a 24-hour hot water supply and poor comfort. 3. Solar water Heater Lighting board must be installed on the roof, both large and bulky, but also affect the beauty of the building (the more obvious the more high-end residential area), but also easy to damage the roof waterproof layer.