Hi Warren -
You're more than welcome to stop by and check out our system sometime to get some ideas - even this weekend - we'll be around. We had a different company do it:
http://www.ebmservices.com/
Jon Harkness is the person who handled our system.
The prices quoted were quite a bit less although it could vary from on install to another - $8600 for a 3-panel system w/120 gallon storage; I believe it was around $7300 for a 2-panel system w/80 gallon storage, but we thought the extra 15% cost for 50% more total output was worth it. Based on the panel costs, it should only be about $1K per panel additional unless that third panel really complicates things. I estimated that had I purchased the items myself, I would have been looking at $5-$6K buying over the internet for 2 or 3 panel system, so for labor, we paid about $2500 - but then you get tax credits that cut that cost almost in half. I can assure you it was well worth $1250 actual out of pocket cost to have them install it
I am suprised the other company is telling you to get rid of the tankless coil if you still leave your oil heat on for backup in the winter. They are correct that a tankless is wasteful when you run the boiler all summer, and avoiding that is really where you save a lot - people who already have natural gas heaters have a much tougher payback argument. But when your boiler is going to be on anyway, it is still the most cost effective way to get hot water.
Ours was installed with valving to run three different ways:
1. Solar only, bypassing the tankless coil, with an internal electric backup element for shoulder seasons when boiler isn't on for heating purposes. This is the most cost effective and simple way to extend your boiler shutdown period. The cost of electric to finish off the heating is still much less than standby losses on the boiler.
2. Solar tank feeding the tankless coil - in the winter, you get some partial preheating of the water which lowers the load on the furnace.
3. Bypass solar tank and run exclusively on tankless coil - really only useful if you need to get into the solar tank.
Addressing a few other questions - the thermal stratification in the solar tanks works very well and better than I would have expected. Two tanks is overkill IMHO. We regularly see 50 degree differences in the bottom vs. top of the tank. As you use hot water off the top, you draw in cold to the bottom, and when the solar system runs, it sends the heat to the low part of the tank. If it's not hot enough by the time it's at the top, then you have an optional electric backup element that can finish it off. Our tank has yet to get below 115 since April so I'm not sure when it'll actually be required - this past weekend, the tank hit 180 and maxed out so it'll be a while before that comes into play. Also, keep in mind that 120 gallons of water at 150-180 degrees goes much much longer than a 60 gallon conventional water heater at 120 degrees. You bleed off much less of the hot water to mix with cold to get up to the temperature you'd like to have at the tap.
The solar tanks also cost close to $1000 so that can be a big cost factor if you use two, while going from an 80 to 120 gallon tank is only about $100 more if I recall correctly.
-Colin
