Monkeybird, have a scan back through this thread - I made a huge post about wood pellets on Sat 23 Feb. But, to cut a long story short, whether you need a mahoosive pellet boiler with equally mahoosive hopper depends entirely on the heat requirement of your house. Can you tell me how many rooms there are in your house, especially bedrooms, whether it's detached, semi or terraced, and whether it is insulated to current standards? And does it have double glazing? The really big boilers are designed to go in a garage or an outbuilding. Ours on the other hand is not huge, sits on a hearth where there was once a Rayburn, has an integral hopper and in the depths of winter could go just about two days between fills - although our house is appallingly badly insulated due to it having thin wooden walls. If it didn't have to burn constantly for at least 12 hours of each day to maintain temperature, it would go 3 or 4 days between fills.
Duchesse, geothermal heatpumps do cost an arm and a leg to install. The point is, once they are in, provided your house is well-insulated, they cost next to nothing to run. The stats normally claim you get your money back in 10 years; in practice I hear tales of people getting it back in 5 or less. After that, you heat your house for next to nothing. However there are some catches:
The cost of the installation is related to the heat requirement of your house. Ours was not favourable due to our paper thin walls. We were looking at a unit capable of an 18kW output, which would cost (if I remember, very roughly) £8k to supply and install. The real killer however was the heat collectors. If you don't have sufficient land to run pipes horizontally under the surface, then you have to go straight down, which is expensive. You need to go about 100 metres per 6kW desired output (very roughly), at a cost of about £4,000 per 100 metres. We were looking at three 100 metre boreholes ... a potential total cost of £20,000, with a maximum grant from the Scottish householder renewables initiative of I think £3,000. We are planning to stay here a long time, but even so, that's a huge capital investment.
The rule of thumb for a successful heat pump is, have an extremely well insulated house, and if at all possible, use it to run underfloor heating rather than radiators, on the ground floor at least. A heatpump supplying 45 degrees c. to underfloor heating will consume 1kW of electricity for every 4kW it produces as heat. A heatpump supplying 60 degrees c. to radiators will produce 3kW of heat for each 1kW of electricity.