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Tuesday, May 22, 2012

Plug-in Solar Panels

Cross-posted from Renewable Energy Report

An article over on CNET titled Got a deck? Solar panels now a plug-in appliance, suggests that you can buy from a 1,000 watt solar panel system that plugs into your wall outlet for only $1,099. I thought they were really on to something until I read the comments:

This article was written very poorly. At first read, it would appear that the 1,000 watt system costs $1,099.95, but going over to Amazon, that is just the price of one panel whose rating is 240 watts.
At about $4.58/watt, these panels will not produce electricity to pay for the finance charges alone. You will not be able to recover your investment on this, as the panels deteriorate through time.
If the 1,000 watt system costs $1,099.95, it would truly be disruptive as it will be feasible. But no, this solar PV will not cut it, still too expensive. If they can just sell these to about $2/watt, then it would be very worthwhile, given that you will mount these yourself.

On the other hand, I think this concept has potential (no pun intended). I bought a cheap solar inverter last year similar to the one in the above article just to experiment with. You connect one end to a solar panel and plug the other end into a wall outlet. The device converts your solar panel’s low voltage direct current into high voltage alternating current. Because the voltage (electric potential) from the inverter creates an electric version of back pressure against the voltage from the power company, it will reduce the amount of power coming into your house from the power line, which will slow down your electric meter, reducing your electric bill.

Modern homes tend to have significant phantom loads (appliances that draw a small amount of current even when you turn them off or when not in use): computers on standby, DVRs, televisions, motion sensors, the clock in your microwave and stove, tuners, routers, furnace, thermostat, chargers, and on and on.
Not many people have a thousand watts of phantom load so purchasing a thousand watt system would be a waste unless you plan to run things like the dishwasher, and clothes dryer etc. in sequence the whole time the sun is shining.

These inverters are intended to supplement your house power grid, not to spin your electric meter backwards. They will not send power (Volts times Amps) to your house wiring if there is no voltage coming to your house from the power company. This is to protect electricians who may be working on wiring inside or outside your house when the power is off. They of course, also won’t reduce phantom loads when the sun isn’t shining.

The inverter I purchased off Amazon cost about $100. It isn’t UL listed so I wouldn’t want to place it anywhere that might start a fire if it blew up. The one mentioned in the above article is, in theory, UL listed. I was testing one out just last week in my drive way. I had it plugged into a Kill-A-Watt to see how much power it was supplying for a given solar panel angle. A neighbor walking by asked how much it was producing. When I said “About 35 watts,” he suggested it would never pay for itself, and he was right. But then again, when did granite counter tops ever pay for themselves, or produce any power for that matter? A system like this could be viewed as a high-end appliance to reduce phantom loads.

I’m not recommending that people run out and purchase these because they are of questionable quality at this stage of their development, and I’m also not sure of their legality. I can envision a day when systems like this that cost less than a $ 1,000 might be (as insulation and double pane windows already are) required by building codes in sunny climates to reduce the impact of the significant and growing phantom loads. And who knows, if the price gets low enough, builders and home owners may start installing them to show off to neighbors.


  1. " You will not be able to recover your investment on this, as the panels deteriorate through time."

    Deterioration over time is almost nothing, 0.5% per year, You will be dead before they are halfway their life.

    " At about $4.58/watt, these panels will not produce electricity to pay for the finance charges alone. "

    jesus, didn't know stand alone unconnected solar PV panels were THAT expensive in the USA.

    My 239 Watt pannels (17 pieces) and 2 inverters did cost me 3.7 euro (4.7 USD) per installed Watt, including mounting all the panels on a above tile roof structure 13 meters high, and putting wiring to my ground level garage, where the two inverters are plugged into the main switch panel connected to the grid.

    The 4.06 kW installation produced recently on a cold windy very sunny day some 27.5 kWh.

    Which comes to a 27.5kWh/17= 1.62 kWh production per panel on that day.

    Or 1.62 kWh / 12 hours 'real' daylight = 134 Wh hourly production per panel.

    Your 35 Watt per hour PV pannel production does therefore not reflect a good solar rays location or there must be another technical issue with your setup, given that Seattle is located at the same latitude as my PV pannels in Belgium, and yo therefore should have more juice.

    My PV pannels produce around 3800 kWh per year, which comes down to a fixed 20 euro cents per produced kWh investment rate, when accounting for a 20 years net PV pannels electricity production, divided by my investment of 15 161.67 euro. (15161.67 euro / (3800kWh per year*20years)

    I installed them in 2010, when grid electricity did cost me 18 cents per kWh. I knew then it would temporarily be a loosing proposition.

    In 2011 grid electricity was suddenly raised to 20 cents per kWh, and in 2012 to 22 cents per kWh, because of many investments in new grid distribution infrastructure.

    I therefore already achieved grid parity in 2011, and started making a profit from 2012 on, just from grid electricity rates.

    Of course, I already did a profit from day one, since approximately 30% of this investment is personal tax deductible, and I receive a grid feed in rate of 35 cents per produced kWh, making me recoup my investment in 7 years, while receiving the feed in rates for 20 years.

    I do not have any qualms about profiting from this situation, since Belgium imports 20% of it's electricity from neighbouring countries, and I pay a lot of taxes that I deem wasted, when seeing governmint efficiency in full display in my neighborhood.

    " And who knows, if the price gets low enough, builders and home owners may start installing them to show off to neighbors. "

    That's for sure. And you will be the first to do it, as I know you a bit . . .

  2. These advantages are global. Hence the additional costs of the incentives for early deployment should be considered learning investments; they must be wisely spent and need to be widely shared.

  3. I agree that the article was confusing, you have to be so careful these days with solar information. Even working in the industry it can get confusing so I pity the poor client who has to get their heads around all this.

  4. I agree that the initial article caused some confusion. I can only wonder what the poor consumer has to go through when deciding on whether to have solar installed.
    Let's get some standardization when discussing solar products and make life easier for our clients.


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