Putting renewable energy onto a less efficient house probably helps more in the long run than putting it on a super efficient house. The utility savings is probably more noticeable with the inefficient house.

Preparing the house for solar should be the first step. Checking for phantom loads, changing to CF, adding insulation if needed, should probably be done first. In my area, the best savings is hot water assist.

Installing a solar hot water system pays for it's self within 8-10 years. Installing radiant heat solar hot water systems are even more cost saving. I estimated that I could convert my 1750 sqft house and have a savings within 5-7 years. (I need heat for 3.5 months of the year) This would be a DIY project; using additional labor ($75 per day per man) Radiant hot water does not require a large boiler. The flow requirements are much lower than forced air systems.

Solar electricity is costly to install. Having a house that is wasteful in energy does not make sense. The cost to add solar panels is much more than the cost to reduce energy needs. Find out what the government will pay for improvements first. The level of involvement can be profitable at one point and costly at a different point.