I live in Vermont, zone 6, where we have 7,771 heating degree days (base 65 degrees). We burn gas in our household for hydronic baseboards; we don’t have air conditioning.

Out of curiosity, I started ball-parking costs for a rooftop solar photovoltaic system, which I would link to a new ground-source geothermal heat pump. I was curious what it would take to get off petroleum and leave the grid, where we get most of our electric power from Canadian hydro sources.

First, the ground-source geothermal heat pump system would run around $30,000. Then, to put up enough rooftop solar to power the heat pump’s compressors, it was potentially another $20,000. We are in a cloudy area and I’d need batteries. Even with the rooftop solar, I would still have to tap into the grid to kick over the 40-amp geothermal compressors. That’s a total of $50,000.

At 5 percent bank rates over 30 years, that’s $270 a month ($3,240 a year), minus the deductibility and the state and federal tax credits. It’s more than I pay for my gas bill now. But my gas payments are in cash, and I don’t have to sop up so much credit nor assume debt to pay the gas company.

Worth it? Not really. In fact, that sort of a solar-geo setup is a trophy system. It’s an impractical fantasy — and bad energy policy — to think it could be viably installed on a house-by-house basis.

I costed-out these energy solutions because of some information I learned from Robert Bryce’s book “Power Hungry: The Myths of ‘Green’ Energy and the Real Fuels of the Future.” As glamorous as it is to express love for solar and look with pride at windmills spinning on ridgelines — believe me, I’m a museum-quality environmentalist — you have to ask if those systems can deliver a meaningful contribution to our grid or energy reserves. In addition, that has to be seen in the light of how much energy it takes to manufacture the alternative generators and how much land is required to make them work.

Robert Bryce points out that California’s peak electricity demand is about 52,000 megawatts, of which around 17,000 megawatts will soon have to come from renewable sources by law. The new California-based $2 billion Ivanpah solar plant will provide a whopping 370 of those megawatts. The size of that solar farm is 5.5 sq. miles. That’s $2 billion to produce .02 percent of the total required renewables.

How about wind?