Can you save money by installing solar panels (PV) on your house?

Probably not economic yet...certainly in Birmingham UK... maybe in Birmingham Alabama !

Most cost effective way to use solar power is for domestic hot water supply.

Is there a high p.v. adoption rate in very sunny areas like Phoenix Arizona? When they are saving money I will consider it for Central Illinois.

Look for opportunities. The economics of each depends upon local circumstances.

The best investment here was low-energy replacement lighting, most of which one can certainly take along when one moves house, extending the investment life. Replacing a 40W incandescent with a 9W low-energy lamp is definitely a DIY operation and can be justified for anything that is on for more than 10min per day regularly, given local tariffs. Another good investment was the pressure-cooker, which saves its own value every six months in terms of shorter cooking- (and therefore stove-on-) time by cooking at around 2 bara instead of 1.

A prominent DIY chain is offering to install wind turbines on the home at <£1500 GBP all-in. A review of the economics locally, given available wind-speed data, indicates a payback of 15-20 years. Given one can't take it along when one moves, it's on indefinite 'hold'. A home-brew solution would give more attractive economics, and there is why there is no end of these for review on the 'net. A different home at a more elevated and exposed location 1.5km away has a commercial turbine installed on its roof and was spinning away merrily at the last observation, pouring its micro-generated power back into the grid while its occupants were on holiday.

Solar collection is hampered here by the presence of a number of trees on the sunny side of the house that shade it. The trees are in a designated Conservation Area and are therefore protected. Making logs out of fallen branches, and using them for space heating, is a good bet, and a dead sycamore 100m away is likely to, er, dum-de-dum-de-do.....

Everything else in the home is lagged as thickly as can be justified and nagging the occupants to turn stuff off when not required works wonders!

There is potential to add micro-generation to the redundant 3kW immersion heater element in the hot water storage tank. A home-brew solution is required.

Replacing the car with a smaller one was easily justified.

What are the opportunities elsewhere? http://uk.ask.com/web?qsrc=178&o=312&l=dir&dm=all&q=energy%20saving%20tips%20home

I built a couple of solar hot water penels, mostly from scrap as a winter build project...they aren't perfect, but they've given plenty of hot water since April.

If you want to build it yourself there is plenty of info' on the web.

It surely would save some money, energy etc if expectations are turned down.

The power to the geyser should be disabled or set only to operate when the water reaches a predetermined minimum temp.

I have seen some installations where the temperature control of the geyser is set too high. The power consumption were even more than without panels. I don't see the need for first running a bath with almost boiling water and later have to cool it down with cold water.

Quite.

The Energy Saving Trust advises 60degC is enough, and any more is wasteful.

I live along the eastern seaboard near Wash D.C. Given the current electricity prices, the amount of energy you can reasonably expect, and the cost of installation of a grid-tie PV system and you find out that the payback is in the 20-25 year range. That is also about the expected lifetime of said PV arrays. Just doesn't make cents to me. (Especially when you consider how much $20-30k will grow in the stock market over 20 years) On the question about the batteries, I would suggest that spinning the meter backwards presents far few issues than maintaining banks of Pb batteries. Of course, your local utility will have to grant you permission to tie into the grid and approve your equipment and installation. Spinning the meter backwards is a more "efficient" energy "storage" device as well. Where PV arrays make the best sense is where the "grid" is a long distance away from a new remote homesite and then you can factor in the connection costs in your payback calculations if you plan to live "off-the-grid". I do however, plan on installing domestic hot water solar collectors in the near future and perhaps also install radiant floor heating as a supplement to my existing forced hot air natural gas fired furnace.

Will your radiant heating be fed by the solar water collectors?

Yes. My plan is to use a closed loop system so I can run food-grade propylene glycol to prevent freezing, eliminating drain back valves and all the carefully sloped plumbing to avoid trapped water outside of the heated envelope. The heated fluid would first pass through a stainless flat-plate heat exchanger, typical of (http://www.flatplate.com) to transfer the heat to the domestic hot water storage tank. My concept is to install an 80 gallon pre-heat tank and retain my 40 gallon gas-fired unit to "top off" the temperature as-needed depending on weather conditions and hot water demand. As long as the fluid has sufficient temperature delta over the inside ambient temperature, and the thermostat is calling for heat, I would then circulate the fluid through the floors before returning it to the collectors. Since this is existing construction, I would use a system similar to this company's offering (http://www.radiantec.com). First level is relatively straigtforward since I have full access to the underside of the floor from the basement. The second story radiant floor heating is more problematic as it will require pulling down the drywall ceilings of the first floor. I'll see if the missus will go for it. Of course I will need the requisite isolation valves and various circulator pumps, temp sensors, a controller, and perhaps a mixing valve to temper the fluid temperature going to the floors to avoid overheating the flooring materials. All this appeals to my psyche anyways. Using my own sweat, blood, and tears where possible, I figure I can keep the overall cost low enough to make it worthwhile.

One writer said that there better bets probably on the stockmarket ! Could be for the future certainly.

However, the cost of electrical and gas energy seems likely to keep rising. Has that been factored in to the various 20-25 year estimates ?

The rate of rise of electric rates seems to be fairly moderate in most areas of the US. But those payback estimates also don't consider the life-cycle maintenance costs of the panels either. One good hailstorm or hurricane can really ruin your day. Keeping the glass clean, if the seals on the panels begin to leak etc. We have not seen these systems in use long enough to fully understand the total cost of PV panel ownership. NASA has good luck with them in space, but most of us still live on this green earth.

We have all heard about microgeneration, I suggest nanogeneration. Instead of mucking around with inverters and investing serious money, take a low power-output solar panel, a free car battery (we can all get one) and pipe 12V dc into the house. Then use linear regulators (or switched-mode if you are clever) one for each item (because each has some unique stupid voltage) to replace all of those stupid power supply bricks that plug in to the mains. You know the ones, there's one for the modem, the answer phone, the cordless base station, active speakers, mobile phone chargers, hand whisks, electric shavers, bluetooth headphone adaptors, bike lights. A bigger panel could probably drive the laptop and printer too. Why not make a pretty panel with labelled switches to make it easier to switch off an item you are not using.

It will tidy up the area and reduce the number of four-way extension leads (one each for groups of things you switch on together).

Have some cigarette-lighter-style outputs so you can plug your mobile phone car charger directly. You can target appliances that run directly from 12V. Of course this might extend the concept away from the "computer corner" but that's up to you. You are engineers after all.

The point of this is to use solar energy on a small scale without too much capital outlay so you can do your bit, have fun, feel green and not worry about payback and amortization and all that stuff I don't understand.

Of course it would be better if they (the manufacturers used switched mode psu's instead of the room heaters you normally get with an appliance).

Oh dear, what started out as a suggestion turned into a rant. My apologies.

That sounds just like the hybrid AC-DC electrical power distribution system within my travel trailer. We have 110VAC/60Hz and 12 VDC but you folks on the other side of the pond would probably have 220VAC/50Hz and 24 VDC. My dad used to own a Ushant motorketch that was Scottish-built with 24 VDC electrics.

Thanks to all for really great answers. You all confirmed what I suspected. At this point in time I can't understand why anyone would install a PV system except if they live too far out and don't have electric service or their service is not reliable. Sola water heaters, as many have stated has excellent payback and reliability. I saw an installation 30 years ago where a guy put a 100 ft coil of 1" black PVC on top of his house and routed the cold water to his water heater through it. It wasn't pretty but he said it saved him $20 to $30 a month ever since.