Exploring Possibilities for Savings

The boiler system is presently configured to start at 6AM, and heat up the DHW tank and provide heat to the floors. It shuts down at 7PM

On sunny days, the collectors begin heating water at 9AM, and by 10:30, the DHW tank is usually up to temp. On week days, I shower at 4:30 AM, and there is still ample hot water in the 80 gallon tank. My wife showers at 6:30, so I have the boiler start at 6AM to make sure she does not run out of hot water. There is still a lot of residual heat left in the tank, even after my shower, all resulting in less propane usage needed. So, there is probably not much savings available (let alone the risk of having my wife running out of hot water) with changes to the DHW system.

What may help with propane savings, is to not let the boiler bring the in-floor heating system up to temp until 10:30, so that the solar collection system has a chance to heat up the capacity tank.

System Saving Money and Pay-Off Projections

The $2000 Federal tax credit this year is the first obvious benefit, and I look forward to future tax credits (30% up to $2000) when I install additional vacuum tube arrays.

But, in the long term, saving on the cost of propane was the goal. My average usage for propane 2005 to 2007 was 1150 gallons. I installed the collection system last summer. My usage for 2008 dropped to 1180 gallons, and the system only began saving me propane the last half of the year. Winter temps have not been exceptional.

More accurate data will take time to produce, but it is not overly optimistic to expect my propane usage to drop to 700 gallons per year. A savings of 450 at $2 a gallon is $900. After tax credit cost of the system was $10,000 dollars, so I am still over a 10 year pay-off.

Installation of an additional 30 tube array should only cost (after tax credit) about $2400, and should further reduce propane usage by at least 200 gallons, shortening the pay-off to below the 10 year mark.