Grid-tie inverter hook up

[Terry Boutilier]

I have a small solar set up and I bought a 400 watt grid-tie inverter, I was wondering what I have to do to connect. I live in nova scotia Canada. I tried talking to nova scotia power and they had no idea what a grid-tie inverter was. will it hurt anything if I plug it into any outlet in my house

[Chris Olson]

Typically, grid-tie installations in both Canada and the US require a net metering agreement with the utility (hydro), a lockable disconnect switch accessible by utility personnel 24 hours a day, and an inverter that complies with UL1741 (not sure of this in Canada).

I don't recall seeing many 400 watt grid-tie inverters that are even legal to hook to the grid. If it hooks up by plugging it into a wall outlet, then I would bet that it's not legal.
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Chris

[Tom Karasek]

One of the major impediments to widespread use of micro power home installations is the lack of utility-approved inverter tie-ins at a very low cost. The components of an inverter are very inexpensive, but even low cost inverters need a safe interconnect to the grid.

The interconnect is basically a relay which trips open when grid power dies for any reason so as not to injure utility workers. Another circuit trips the relay if homeowner generated power is not voltage, frequency and phase compatible with the grid. Once these conditions are met, the utility must purchase any power above homeowner needs.
Several homeowner generated power sources run 24/7, so even a small amount of homeowner power can exceed home usage a few or several hours a day. That excess power can be a significant offset to home system cost and eventually pay it off. Also the many possible home sources can add to a huge amount of power the utility need not generate.

My question of the group: Is there an inverter tie-in package, with or without inverter, available at only a modest profit margin above component costs? If not, why not?

[Chris Olson]

The cost of equipment is only one aspect. In Wisconsin a grid-connected system has to be state inspected. The cost of the state inspection alone is slightly over $1,000.

With the cost of electricity from the grid at .15 cents/kWh you have to generate almost 6,700 kWh just to pay for the state inspection cost. 6,700 kWh is better than half the amount of electricity used by the average home in a year. With micro-generation it is doubtful you will ever even cover your costs of the required inspection, much less equipment.

The undeniable fact is that it is more expensive to generate your own power than it is to buy it off the grid. You have to have other reasons for doing it than money, because it is economically not feasible without utility or government subsidies.
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Chris

[Rob Beckers]

Chris, for solar PV we are actually rapidly moving towards grid-parity for much of North America, though not yet for very small installations (ie. the 400 Watt mentioned by Terry).

To give you the numbers: Installed cost, including all permits, inspections, engineering (required here, stamped analysis, $2,500), for 10kW of rooftop solar PV is just about $50,000. That really is soup-to-nuts, including all costs. With our solar resource (southern Ontario) we can very reasonably expect that to produce 285,000 kWh over the 25-year warranty of the panels. That works out to 17.5 ct/kWh.

Put up solar with net-metering and you're in essence locking your electricity rates in for 25 years to come at that rate.

Ontario currently charges around 15 ct/kWh, after including all taxes, fees etc, and that is slated to go up 7% this year alone.

Wind is a very different beast though, and very much harder to reach grid parity. Very few places in North America will ever get close. As you say, you have to do it for other reasons (or if a grid connection runs $75,000 because your house is too far from the grid it may pay for itself from day-1).

-RoB-

[Chris Olson]

The other thing is that I expect the price of grid electricity to double in the next 5-6 years. I think it took 5-6 years in the last cycle to get a doubling in price. So that has to be factored in, but it's a "fudge" factor because nobody really knows what the exact price will be in 10 years.

So no matter how you look at it, grid-tie is a hard sell looking at it from an economics standpoint, unless there are subsidies involved that either help with buying the equipment, or pay you an inflated price for the power you generate.

For off-grid folks any money you spend on an RE system is an investment and raises the value of your property. There are people from the big cities that will pay premium price for off-grid retirement or vacation property that is out in the boonies off the grid. We could've gotten utility power run to our place at one point (about 10 years ago) for $160,000. I don't know what it would cost today. We got roughly $40,000 in our power system and we live pretty darned comfortable with no grid power. I think that's the real value in an RE system because economics aren't involved. Anything we install is paid for the day we buy it. It has to do with independence of the grid system and the lifestyle more than money.
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Chris

[Dave Turpin]

Wouldn't increasing the cost of grid power make grid-tie systems MORE feasible?

[Tom Karasek]

Raising the cost of grid power to homeowners would shorten the payback time but would not be a saving to the homeowner. Similar logic is tried to promote alternative fuels by raising the cost of gasoline. Strikes me as trying to push a string.

Far better for the homeowner to be able to buy an inexpensive tie-in so he/she gets payback for extra power generated. Better for the environment too if thousands of homeowners can afford to provide part of utility needs rather than the utility building more power generation plants and/or burning coal or oil to generate that amount of power.

The inspection cost is mostly just a tax and should drop if thousands of identical home installation kits are available.

[Chris Olson]

Better for the environment too if thousands of homeowners can afford to provide part of utility needs

But it's not good for the utility. The utility is in business to make money. Most of them don't like to mess with grid-tie systems smaller than about 10 kw generating capacity.

It's an unfortunate fact that nothing much in RE is "inexpensive". And if it appears to be, you usually get what you pay for.
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Chris

[Tom Karasek]

Our PUD is a public utility to serve the public not make a profit.

Agree that current (no pun intended) tie-in prices are high. My point is looking at the components there is no justification for those prices.