In a ranking of best to worst, the following are a list of water heaters that are environmentally friendly and produce the least greenhouse gas emissions with estimated annual C02 emissions based on a standard home and a family of four:
- Solar Water Heaters currently rank highest on the most environmentally friendly water heaters; however, they do still emit some carbon. This is mostly due to the fact that they systems require a pump – often electrically powered – and a back-up conventional tank to ensure adequate hot water supply.
- Tankless Water Heaters rank second because they offer both less energy consumption and convenience. In order to notice energy and greenhouse gas emission savings, it is important to keep energy use constant (suddenly using your Jacuzzi after installing a new tankless system). But, if the hot water usage is kept the same, carbon emissions will be 50% less.
- Conventional Gas and Electric Water Heaters are the least favorable for environmental friendliness, with electric water heaters being the very least favorable.
Electric water heaters are powered by fossil fuel burning plants with only 30-40% efficiency. The coal or gas used to produce electricity has produced significant amount of greenhouse gas.
For those eco-friendly and cost conscious homeowners, the best choice is the conventional natural gas water heater.