Marc, this is definitely a new question for me. And in advance, you’ll have to bear with me since I’m a mechanical design engineer… electrical engineering is, for me, swimming in unfamiliar waters a little bit. In my line of work typically when people look into alternative energy options (especially for homes) they’re considering wind turbines of, like you mention, photovoltaics or geothermal [heat pumps].

Though fuel cells are primarily thought of by most consumers in the same associative thinking as cars, you’re right in stating that they could be used to power a home. I won’t go into too much background on the geothermal and PV technologies backgrounds here; save for several brief statements, as there’s plenty of other information on this site alone in which you could (and I recommend you do) research.

But first, before you begin any project with potential renewable-energy or energy-saving strategies, especially when considering your options, you should check out one of my most recently plugged websites these days, http://dsireusa.org. DSIRE is the Database of State Incentives for Renewables & Efficiency, was founded in 1995, and is an ongoing project of the North Carolina Solar Center and the Interstate Renewable Energy Council (IREC). It is funded by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE), primarily through the Office of Planning, Budget and Analysis (PBA). The site is administered by the National Renewable Energy Laboratory (NREL), which is operated for DOE by the Alliance for Sustainable Energy, LLC.

And besides that whole mouthful of information, it’s a great resource for someone in your position. At DSIRE, you can search for tax credits, rebates, grants, etc by state and it automatically separates out the residential programs from those dedicated to commercial buildings.

So, you’re looking at three options. For each option I’ll include a little summary information, opinion of probable cost of implementation for a common system and percentage of power savings (this will assume that all power usage in the home is electric, which may or may not be the case). Cost savings (which you could use to calculate simple paybacks) will depend on your local utility rates. So for our purposes, even though there is no ‘typical’ home, we’ll assume you’d use 1,500 kWh/month.

Option #1 – Fuel Cell

By far the most well-known company when it comes to modern fuel cell technology used to power commercial buildings is Bloom Energy. Bloom Energy founder K.R. Sridhar estimates that a Bloom Box for the residential market could be out in 5 to 10 years and cost under $3,000. So fuel cells for use in residential applications just aren’t very well-developed yet. While there are federal tax credits for fuel cell systems, it’s worth noting that this doesn’t expire until 2016, so we have some time until the market really opens up on this.

It seems that two of the residential Bloom Boxes would be able to power the average American home, though there are associated operating costs to be taken into account (hydrogen or hydrogen generators, Methane (or other hydrocarbons) and oxygen in the case of the Bloom Box). What I could find on the market right now was a 1kW system for $4,500. So let’s say implementation cost of $9,000 + operating costs for 100% power generation.

Option #2 – Photovoltaics

Achievement of 100% of a home’s power from PV panels would be ambitious, I think, and besides requiring a large array area, should include a detailed and energy efficient design of the home from the beginning to minimize energy needs and decrease the amount of PV cells needed. But assuming that isn’t the case, it seems that a 2kW PV system could cost on the order of $18,000. A more common implementation of a home PV system is typically something like a 200W kit for $2,000.

Option #3 – Geothermal Heat Pumps

Okay, heat pumps… I’ll start by throwing out there the fact that you’ll never get the electricity you need to power your home from ground source heat pumps. They can save about 40-50% on your HVAC energy consumed (which in turn can be about 50% of the total energy used in a home) but it just doesn’t add up to 100% any way you slice it. A residential geothermal system could also cost on the order of $18-20,000.

Now, not paying attention to availability of these systems, fuel cells definitely seem the way to go. But since this really isn’t as viable of an option (or as widely implemented) currently, you might want to consider implementation of both a geothermal heat pump system and a renewable energy component such as PV until those fuel cells are out on the market. They’re all likely eligible for rebates and/or tax credits in your area.