Hot Water Storage Tanks
Many buildings have hot water storage tanks. While wrapping a standard tank with an insulation blanket does provide some additional protection against heat loss it is far below the efficiency of a highly insulated tank. In addition, care is needed to insure the blanket does not cause tank damage such as condensation build up.
Highly insulated tanks normally are made of steel, poly/plastic or stainless steel. In all cases they offer a superior level of insulation, often in the form of foam. Not all are created equal and there are significant differences in heat loss. Large capacity tanks are often used for solar hot water storage. Smaller units supply basic domestic hot water needs.
We always use high efficiency tanks for solar hot water storage and there are a number of excellent choices. Factors to consider include:
- Weight of tank – heavy tanks are hard to move
- Size – will it fit though all required doorways
- Degree loss per day – Some tanks are as low as 5° loss in 24 hours
- Glass lined – can crack, care is needed in transport, heavy
- Stainless steel – very durable, expensive, excellent for corrosive well water
- Poly (Plastic like) – lightweight, excellent for corrosive well water, inexpensive
- Warranty period – is warranty transferable?
Some tanks have built in electric elements. We often use these as solar backups, since they do not come on often. Some tanks have dual coils. This allows two different “circuits” to route through the hot water. For example in a solar thermal hot water system, one coil may have the solar heated hot glycol that is used to heat the water in the tank. The second coil may be for a radiant floor system or a boiler backup. Some tanks have many coils and multiple inputs/outputs.
If you have a standard water heater, replacing it with a highly insulated unit could dramatically cut your fuel bills and have a payback time of just a few years. Most are energy star rated and are eligible for government tax credits. As part of a complete solar hot water system you tank would qualify for the solar incentives
We often recommend Marathon tanks. They run about double the cost of a standard tank, but have a lifetime warranty to the original homeowner and a heat loss of just 5° per day. They quickly pay for themselves. They are also eligible for the Efficiency Maine weatherization program and federal energy star tax credit.