I have just about decided a grid tied PV system for power is my best option. Now I need to educate myself, and your help is appreciated. How do you calculate the size of the system? I'll do a ground mount so how far away from the house is too far to set the panels. What is/are the difference(s) between mono and polycrystalline panels, Although LED lights are pricy, are they ultimately worth the investment? Am I correct in thinking all panels need to be the same watts? I have done away with a clothes dryer, and oven, I know both are energy hogs, but I will buy an induction range for the kitchen. Other appliances will include a hydro-radiant floor heat system and that boiler draws a lot of amps, a refrigerator, and a chest freezer, lighting, computers, TV, and other domestic stuff. I would like to size the system to break even with the electric company with the possibility of going off-grid sometime in the future. Your advice is appreciated. I almost forgot, please KISS, my old brain is running slow. Dan

How do you calculate the size of the system?

It depends on what your goals are.

how far away from the house is too far to set the panels.

Depends on the nature of the panels and inverters.

Although LED lights are pricy, are they ultimately worth the investment?

Yes, they use quite a bit less electricity over their lifetime.

Am I correct in thinking all panels need to be the same watts?

Not necessarily, depends on what kind of inverters and how many, but why would you have different panels on purpose?

a hydro-radiant floor heat system and that boiler draws a lot of amps

Wouldn't a heat pump be easier on the electricity?

I would like to size the system to break even with the electric company with the possibility of going off-grid sometime in the future.

That's a big commitment unless you can buy and mount a very large PV system. It's usually better to downsize your current usage, monitoring as you go so you have a good idea of how much juice things take.

In order to meet your electrical usage, you need to determine what your usage is, or will be if you are building a new house. Once the usage is known, then you can use PVWatts (http://pvwatts.nrel.gov/) to compute the output of the solar PV system for the solar insolation in your area and the orientation of your panels. Grid-tied systems can be cost competitive with utility provided electricity, depending on utility rates and solar insolation in your area. Off-grid systems require many more panels, batteries, different inverters, and are almost never competitive with utility provided electricity if it is easily available, and they have significant maintenance associated with them. Off-grid systems must be sized to meet your needs at the worst times of the year, and suffer the additional inefficiencies of battery storage. Average annual usage per U.S. household is 10,837 kWh (http://www.eia.gov/tools/faqs/faq.cfm?id=97&t=3). However, many households use something other than electricity for heating, and that would be a major usage factor.

I live in an area with high solar insolation, and can more than meet all my electrical needs with a modest sized, 3.15 kW, grid-tied system. However, the house uses natural gas for heat, and the house was designed to minimize energy usage. Electrical energy use for this house averages about 3300 kWh annually.

You can find more detailed discussions about solar systems at the Northern Arizona Wind & Sun forum, http://www.wind-sun.com/ForumVB/forum.php.

...and you asked about the difference between mono and polycrystalline silicon solar panels. The general recommendation is to just use the rated power for the panels, independent of the crystal structure. I have not seen much differences in comparing mono and polycrystalline systems in this area (http://www.residentialenergylaboratory.com/comparison_of_pv_systems.html).

Thanks IFC, I'll look into heat pumps.
Lee, thanks for the links.
Dan

The real energy hog at the kwh trough in all but the tightest and highest-R houses would be the electric boiler. Better class ductless mini-split heat pumps would use about 1/3 the amount of electricity (or less) that of an electric boiler over the course of a heating season in most US climate zones, cutting the size of the PV array needed to support that load considerably. Yes, that's a 2/3 power savings! In most homes heated electrically, the heating is far and away the largest single power use, bigger than all of the rest combined. It's the long duty cycle, not the peak power draw that makes the difference. (The dryer may draw a lot of instantaneous power, but only for an hour a day or so.)

In the cold edge of US climate zone 6 and higher it might as much as half the power use, and in the mild warm edge of zone 3 & lower it'll be about 1/4 the power use. Mini-splits are not as cushy-comfortable as warm floors under foot, but they're not bad, and provide very stable room temperatures compared to most air-delivered heating systems.

Going off grid with electric heating (even leveraged by heat pumps) is a non-starter. Wood or fossil fired backup to a well designed passive solar approach is the most common. Sometimes active hydronic and solar-thermal with large buffer tanks can work, but that's an expensive proposition up front.

Thanks Dana1,

Always good to get your input.

As a baseline systems between 4kw and 6kw can often offset a whole houses energy requirements. As indicated in others posts this may require you to bring down your energy consumption to achieve that if your needs are higher. Systems based on micro-inverters like the ones made by Enphase can actually be expanded easily over time as well. So you could get started with a system on the lower end of that and if you can't get your consumption down to match it, then you can always expand it later. I like the mini-split heat pump suggestion above. Keep in mind that in climates like where I am in Vermont a mini-split may have to be supplemented during prolonged cold spells. I heat with a gasification wood boiler and have a thermal storage tank that lets me get my domestic hw from wood even in the summer. I have no oil or propane bills at all. Once I get enough solar pv in place I hope to not have any outside energy costs.

Compared to CFL lights, LED lights aren't worth the investment in most applications. But it's getting closer.

Micro-inverters like Enphase work well, although the cost is higher (~$.65/watt).

Make sure you are going to live in the place long enough to see the return on investment.

As others have pointed out, first thing to know is what is the electrical usage. The is a free program called BeOpt that allows a good estimate to be made. There is a learning curve; the use of the program will educate you quickly about your housing design choices and costs. If used correctly, it will tell you what the annual usage is going to be.

You do not have to plan on living in the house long enough to recoup costs. In may regions, buyers will pay at least some part of your added costs back when you sell. Solar PV often generates a return of cost in the range of 35-75%. Note the cost is the current cost of the solar; if you paid $40,000 for a 6KW system 5 years ago, but can buy a 6KW system today for $20,000, a buyer might pay you 40% of the 20,000 cost; not 40% of your original $40,000. Some PV sales agents can refer you to appraisal studies to learn what you might expect on resale.