[johnsjmc]

I designed and installed my own system for about $8500 in 2005 before the big govt grants (the average price is now 20k with a grant covering about 1/2. Funny how that works.
My HP was 4 1/2 ton . The problem I wasn,t completely aware of was the output is rated at an incoming ground water temp of 4 deg C. and falls about 20% at 0 deg C.
My system ran about 5 min on 20 off in the beginning of the heating season but was running almost constantly by the end of the season as ground temps fell.
A larger HP would have run less . The collecting bed was oversized for a 4 ton and could have supported up to 6T.