How practical would it be to build a modern home that powered itself with solar panels?

Forgive me as I don’t have a very good idea of the numbers or the specific issues which would be involved here. But say someday I wanted to build a house on a reasonably-sized lot (whatever size that is) that would use about as much as energy as your typical Western middle-classed family of four uses.

How feasible or practical would it be to have that house powered entirely, or at least mostly by its own solar panels (which could be on the roof of the house as well as additional panels installed on the lot)? Would it take a lot of maintenance once it was set up? Let’s assume the house is still on the electrical grid but we wanted it to use all the solar power it could first, and only draw power from the grid as reserve power once that is spent. For night time power usage, how/where would the energy be stored? How many panels would it take? (again assuming typical energy usage; any remotely reasonable ballpark estimates would be fine)

Energy usage varies so widely between residences it’s really not easy to say one number. Now that I’m in an apartment I’m using about 2/3rds the energy now than I was when I lived in a larger house, and I live alone.

The problems you have to solve with solar are the cost of the power inverters, the panels themselves, and the battery bank to store the electricity. You’ll also need to know how much sun you get in your climate, and backup power generation. Also, Tucson residents wouldn’t need as many solar cells as Seattle residents. Sites like www.homepower.com and Mother Earth News help with figuring out your actual power requirements.

Since you’re building the house, make it super-insulated to cut down on the heating and cooling you need.

Buy the most energy efficient appliances you can. I’ve read that you get three times the benefit per dollar buying energy efficient appliances Vs. buying more solar panels, but thats ten-year-old info.

I don’t think it would matter much. Let’s say without the solar panels, you excluded as many extra appliances as possible, and purchased as many energy efficient appliances as you could. Typically, your energy bill would be ~$100 per month. Then, you installed a whole bunch of solar panels and equipment for an investment of say $10k which reduces your electricity use to 0. However, the electric company will still charge you taxes and maintenance fees of say $30 even if you don’t use any of their electricity. To get back that $10k investment, it would take 12 years.

If you’re still hooked up to the grid, then the logical way to “store” energy for night is to sell your excess back into the grid during the day, and buy it back at night. Depending on where you are, the power company may even pay you more for the electricity you sell than it charges you for the electricity you buy, since you’re selling during peak hours.

If this is a long-term goal, I recommend the Mother Earth News as well. All their back issues are online but a subscription is pretty cheap. The reason I recommend it is that it is an alternative lifestyle magazine but they cover some real characters that have actually done this type of thing and a story about how it works for them day to day plus some hard numbers. The raw science isn’t that hard to run numbers on but their are practical implications to take into account as well. Total electrical self-sufficiency is fairly difficult to accomplish in most areas so you have to decide how far you want to take it. You aren’t limited to solar power however. Wind power and maybe even small-scale hydroelectric can be used as well depending on the property there are large upfront costs with those as well.

There have been some recent breakthroughs in solar panel efficiency that you may want to take into account. Like most new technology, the price will come down on the cutting edge panels of today so it may be wise to start planning now with real numbers that you are willing to act on when it is feasible.

Selling back electricity at your peak generation times is a real possibility and a good idea. The grid as a whole doesn’t know or care where the power comes from so it isn’t cheating to produce, use, and sell back in the best way you can. If the goal is to save money in the long-term, that requires a complex set of financial assumptions because the upfront costs on solar installations are not cheap and take time to pay for themselves if they ever can.

Consider combining wind and solar solutions: http://www.youtube.com/watch?v=WZ5kX5Yw4eY

Also if you’re in a cold area, passive solar (big windows on the South side) makes an enormous difference in energy usage.

I do not have the figures anymore so I am going off memory, but I looked into solar panels for my home last year. To knock an average of $124 off my PG&E bill the up front cost was in the range of $26,000. With the tax rebaits it would drop to $16,000. The life of the panels was 10 years guaranteed.

My brother who is not tied to a utility also looked into a complete system with batteries for storage. The cost was in the area of $50,000. He descided it was cheaper to buy diesel fuel for his generators.

If you are tied to a utility the storage would be the utility system, if not tied to a utility you would need batteries.

If building a new house the panels could be incorperated into the roof system rather than on top of and would save some construction costs.

As others have said, it’s possible (though very expensive) to simply build a large-enough solar-electric system to simply plug in in place of a grid connection, but this is not the cheapest way to do it. The cheapest way is to reduce energy usage first.

Existing North American houses are so energy-inefficient that there are plenty of things you can do to reduce energy use before you even touch the supply. However, some of the greatest techniques for capturing and storing energy may be difficult to implement in an existing house. This is extremely dependent on the type of existing construction, the orientation of the existing house, etc.

If you’re building new, you have a lot more freedom. And if you have not yet chosen your site, you have even more freedom. When people think of providing energy for their houses themselves, they gennerally blur two separate things: the provision of heat, and the provision of electricity.

I’ll look at heat first.

Basically, in a house, you have to provide heat, store it, and keep it from leaving. You can provide the heat via a furnace or stove, but this costs money for fuel. This cost can be reduced by capturing the light and heat of the sun through windows facing the equator (south for us in the Northern Hemisphere).

You then store the heat in thermal mass: walls or floors of rammed earth, concrete, or stone; you can even use tubes of water. Thermal mass also slows down the rate of change of temperature in a house. If you leave the door open, incoming air will be warmed or cooled to the temperature of the walls.

You seal the house, closing all those little cracks and joints, so that you don’t have to heat as much air. You have to have a certain amoint of ventilation (in Ontario, it’s 0.3 air changes per hour), but you can then manage it through a heat-recovery ventilator. Or by simply opening the window.

Lastly, you insulate the heck out of the house. Place a vapour barrier on the warm side of the insulation to keep water from condensing in the cold parts of the wall.

Such a house, capturing heat and storing it, is a solar collector. You don’t need an active heat-collection system to warm the house, because the heat is already where you want it to be.

Then there’s electricity. You can make it locally using photovoltaic panels, wind generators, hydroelectric generators, or even fuel-fired generators (diesel, for example). But these all cost.

So the same kinds of principles to reduce the planned energy usage apply. Put wall warts, and devices that never truly turn off, on power bars so that you can switch them off when they aren’t being used. Use compact-fluorescent or LED bulbs intead of incandescent. Design the house so that work areas are daylit. (Artists know about this, choosing north light (in the northern hemisphere) for its colour qualities.) Use task lighting instead of lighting a room.

And, critically, if you’re going on locally-generated electricity, avoid extensive use of anything that heats via electricity.

You’re okay with running a small appliance for a few minutes, but electric stoves, water heaters, and dryers are the three most electricity-consuming appliances in the house. Not supplying them through solar will save tens of thousands. So you get a stove that burns gas. Or wood. And you get a gas dryer. Or hang your clothes up to dry.

You can store your locally-geneated electricity in batteries, just as you store your heat in thermal mass. This gives you some leeway with respect to large electrical loads; you fill the batteries with your solar panels or wind generator over time, and then you can draw them down, for a short time, to supply a heavy load like a toaster.

By doing this kind of design, you reduce the loads you have to supply, and then you greatly reduce the costs of that supply.

I have a good friend right down the road who lives off grid.

Her solar setup cost $35,000 five years ago for batteries, inverter, panels, etc.
She has wood heat/water heating/cooking (with propane backup), the solar basically only has to power lights, computer, washer, cell phone and charging other battery powered tools.

Her system works great four months out of the year. Four more are iffy and must have generator backup on occasion. The other four are pretty much all generator, all the time.

And now, five years later, she needs new batteries (to the tune of about $6500). Makes that $4000 the power company wanted to run the lines look pretty good.

But of course, she is a hardcore seventh day adventist kind of sect…the end of the world is coming, etc, etc. So, don’t put your money into starving children or anything like that. Spend it on expensive vegan food and a very expensive fortress against the infidels (that would be me), while trying to convert all of us because we MIGHT be one of the lucky 144,000. :confused:

I forgot to add…solar also keeps the water well pump going.

A couple years ago, I was looking at solutions to go totally off grid since “the grid” wasn’t available where we were looking to build. IIRC, it came to about $50,000 combining solar and wind (mostly wind) to maintain the same level of electricity usage as we current do. And that was without the battary bank since I still insist flywheels would be the more environmental-friendly choice if the actually made then for home off-grid usage.

Depending on what you mean by practical, perfectly so since it actually exists.

  1. There are lots of so-called “passive houses” in Germany that have been built, so it’s possible.

  2. What kind of evidence would convince you? Because I’m fed up with the cycle of “solar works - no it doesn’t in the US - it pays off - no, not in 5 years - etc.” that always comes up when discussing solar.

  3. Are you offside the grid or not? If you only want to come out with net use of zero energy, but have grid access, then it’s very easy to feed power into the grid when you don’t use it, and supplement from the grid during the night.
    If your aim is indepence in the boondocks, then you have to look into storage solutions, unless you can time all your power use to daylight, and have no snow winters at all.

  4. No realistic solution is only PV solar panels, because you still need to heat the house; for that you would combine with thermal panels and a big water storage tank (90 to 120 liters) for warm water and heating.
    For indepence, a wind wheel or falling water generator would be a good supplement. Batteries are problematic. Energy storage via hydrogen and fuel cells is possible, but you need to be sure to safely story the hydrogen.

Steve Ciarcia of Circuit Cellar magazine built a batteryless grid-tied system at his Connecticut home:

http://www.circuitcellar.com/archives/viewable/209-Ciarcia/
http://www.circuitcellar.com/archives/viewable/211-Ciarcia/index.html

It has a peak power of 10 kW and produces about 1 kWh each month. In other words, each month he generates enough energy to run a hairdryer for 1 hour.

After CCEF rebate, his out-of-pocket cost was $60,000.

What a dumb move. That $60K could have bought a lot of electricity from the power company.

Oops, meant to say it produces 1000 kWh each month. Still not worth $60K, though. If we assume electricity from the grid is $0.15/kWh, then using 1000 kWh each month from the grid would cost $150. If we ignore the time value of money, maintenance, and other stuff, it would take 33 years to break even.

Funny no one mentioned berms. A friend of mine lived in a berm house in Minnesota. It was essentially underground with one large south-facing window. It didn’t need much insulation and needed only modest amount of heating in the winter and never got hot in the summer. Another good source of energy efficiency is heat pumps. You can either drill down 500 feet for a reservoir or, if you have enough land, bury the equivalent amount of pipe 10 feet underground. This will provide heat all winter and air conditioning all summer for a modest expenditure of electricity. If you want to generate that using solar panels, go ahead, but your electricity needs will be so modest that it might not pay. Assuming you can connect to the grid. If not, I would get a diesel generator.

You mean this? They fall under one of the sub-categories of passive/ 3-liter/ low-energy houses. It’s true that in the US apparently a lot of electricity is wasted on heating/cooling, but you still need electric power for TV, internet, lights etc.

As others have mentioned, solar costs depend heavily on location, and willingness to conserve. The cheapest watt/hrs are the ones you don’t need to generate.

This is an important point, and too frequently ignored in discussions of co-generation. Fixed fees are typically structured so that smaller users get soaked and big users get a bargain. Even when you sell excess power to the utility, you pay for the connection that makes that possible. You really do get punished for reducing your consumption to very low levels. Like the credit card companies who label those that pay off their balance every month “deadbeats”, Utilities see those who use the grid only for backup as freeloaders. They, after all, maintain all that infrastructure so that they can sell power.

Solar power is far more viable in remote locations where the price of running utility lines is the competing proposition, and in some cases this will allow break even the minute it goes online.

While it is certainly true that it takes the same money to maintain a power line that supplies 1 KWh/month as 1000, it tends to discourage conservation. If we are serious about conservation, and alternative energy, then the big users need to be made to carry a larger burden with regard to the fixed costs.

Berms: Mind the radon levels.