Addition of multiple sources of heat to a home is so worthwhile. With such combisystems, all rooms in a building can be heated up to the required temperature needed throughout. In most cases, antifreeze solar heating systems can be added to a home heating system by including more than one solar collector for a given space heating load. An ideal hydronic combisystem has solar collectors, a gas boiler backup, water heater, and hydronic floor. Basically, it includes four components; two heat loads and two heat sources.

Understanding Economics of Each Solar Space Heating System

Solar Space Heating System Retrofit

This can be achieved through examining the winter solar resource and the duration of the winter heating season. The capacity of a storage tank of a typical solar water heating system is usually 80 gallons with two collectors. This system has an estimated installation cost of around $8,000. If the tank is replaced with higher capacity tank of 120 gallon and an extra collector is added, the estimated cost rises to $11,000. Out of this calculation, a single collector costs around $4,000, but the third collector costs $3,000. Assuming that the heating season is 6 months, this indicates that the additional collector will be used for only 6 months.

Solar Space Heating System

Bearing in mind that the system evaluation above has been installed in an area experiencing a lower winter solar resource, the value of the third collector will not catch up with the other existing two collectors. According to the calculation above, the third collector obtains a quarter of the entire production of the other two collectors. Therefore, to retain the benefit of the initial system at the same cost, the extra cost of the new solar space heating retrofit should be $1000 instead of $3000. However, you should note that economics of the system will vary from one region to another.

The duration of heating season is calculated using the heating degree days (HDD) every month in the solar radiation information. For different regions, the heating season changes from certain months if a given month has fewer heating degree days. For instance, a month with less than 100 HDDs shows 3HDD for every day, meaning a small amount of passive solar gain is still significant. The average solar resource is usually indicated as KWh per square meter/day for 5 distinct tilt angles, and the data is provided with a monthly and cumulative average. Therefore, calculating the solar resource for a heating season, the resources of heating season months are added, and then the total sum divided by the number of months.

The value of solar space heating system will also be influenced by the cost of installing extra collectors, value of displaced fuel, and any available incentives. However, if the additional collectors are used for summer heating application such as pool heating, the collectors will be as advantageous as the home solar water heating system itself as long as the cost is same per collector.