How to hookup micro inverters?

shift · March 2014

I'm thinking of adding a few larger panels to supplement my electrical bill.
In the Older systems this requires a large grid tie box.. I'm seeing micro inverters popping up the last year or so.. So these just string together then hook up to any electrical panel in your hose or how do you attach them to your home "grid". If one tapped into the electrical. Box would it draw from panels first then the grid?

They seem like they are a mini grid tie but I'm not quote clear on it yet

Cariboocoot · March 2014

Re: How to hookup micro inverters?

To certain extent the micro-inverters are put together on a common line. But the same rules about back-feeding apply whether it is done with central inverters, micro-inverters, or a combination of the two: 120% of the main service bus bar rating from all power sources.

So if you've already got grid-tie solar chances are the service panel's rating has been maxed out already and you can not add any more.

As for how the power goes that too is the same: grid tie inverters supply current to the wiring. They don't care nor have any way of knowing where it goes after that. Any power they produce that isn't used by household loads will be sold back to the utility. If the loads exceed the inverter's capacity the extra need is made up the utility. There is no "power goes first to" about it.

shift · March 2014

Re: How to hookup micro inverters?

So in theory i could hook it up to a electrical plug and it would work? (to do it properly it would be wired into a sub panel with a shut off).

I found panels for about $1/watt within canada that i'm very tempted to buy. I still need to calcualate how much the actual pay off would be and over how long to see if its justified.
My roof is more West and only slightly south. From what read you get about a 15-25% loss over having a south facing roof.

I was thinking of putting a few panels on the roof with some M215/M250 micro inverters.. aside form the panel/ mounting hardware/micro inverter and bus wire... is there anything else required?

Price/watt is about $1-1.12 /w plus the cost of micro inverters
Price of local power: $0.08 for block 1 then #0.1295 for block 2

My last energy bill was $389.60 for 3097 KWH over 61 days.
Yearly aveage is 41kWh/day (last bill its was 51)

So if the my area averages 3.66 KWH/m2/day and i have a 1KW array at say 75% efficiency (facing more west then south) I would actually be getting 2.745/KWH/m2/Day.

On 1KWH at 12.95 centers/kwh it would only save me 35 cents a day? or about 10.66/month per killawat of array? am i calculating this right?

Edit - looking at google earth the roof looks to be more WNW.. which may further reduce efficiency

so the question is.. is it worth it?

mike95490 · March 2014

Re: How to hookup micro inverters?

shift wrote: »

I'm thinking of adding a few larger panels to supplement my electrical bill. .....

Solar Power Tools and Calculators http://www.projectfreepower.com/solar-calculatorss-tools

Link in your .sig seems broken

shift · March 2014

Re: How to hookup micro inverters?

Sadly the site got hacked a while back and my very old backup was missing a ton of the updated goods.

Cariboocoot · March 2014

Re: How to hookup micro inverters?

shift wrote: »

So in theory i could hook it up to a electrical plug and it would work? (to do it properly it would be wired into a sub panel with a shut off).

No, that would be an illegal installation. You still can not exceed the 120% rule and you can not legally install inverters by plugging them into an outlet; they must be hardwired. (This has been discussed repeatedly on the forum and we're not going to listen to the "yes you can" lobby of the mislead.)

I found panels for about $1/watt within canada that i'm very tempted to buy. I still need to calcualate how much the actual pay off would be and over how long to see if its justified.
My roof is more West and only slightly south. From what read you get about a 15-25% loss over having a south facing roof.

You can use PV Watts to get a fair estimate of how much power you'll get from a given install.

I was thinking of putting a few panels on the roof with some M215/M250 micro inverters.. aside form the panel/ mounting hardware/micro inverter and bus wire... is there anything else required?

Yes; co-operation from the authorities. Even though you have grid-tie this would constitute a change in the agreement which they'd have to agree to.

You'd probably be better off all around to spend the money on further conservation efforts.

solar_dave · March 2014

Re: How to hookup micro inverters?

I will just echo the Coot's warning. One consequence to a gorilla grid tie is you bold advertise the panels but have no interconnect agreement or permit pulled you are inviting a meter pull by the utility and a code violation with your AHJ. The AHJ may even go so far as to condemn the property until the violation is corrected.

If you want to go ahead do it right, pull a permit which requires a electrical drawing at least and possibly a structural drawing. Contact your utility for the interconnect agreement. There may be requirements for labeled disconnect, locations allowed on the roof ...

Oh I almost forgot, some meters don't run backward, only forwards and your power produced may actually get charge as power drawn increasing your bill.

shift · March 2014

Re: How to hookup micro inverters?

If i'm going to do it... i will do it right. (i'm assuming it would be hooked in through a sub panel).. and yes with permist considering i would have a giant flashy array on the roof!

My real question is it feasible or worth value in my situation. Despite my large bills my price per kWh is relatively low at 12.9 cents compared to other ares.. now in 10 years from now i'm sure this wont be the case as it slowly creeps up. Panel's are much cheaper then when i looked a few years ago.. and finding them at $1/watt has perked my interest again.
Are my calculations correct that for every 1kW array at an average of 3.44 sun hours = about 44cents in savings?

The odds are its a better investment to upgrade windows and other things to make the house efficient but solar is one area that i have always liked to play with

Cariboocoot · March 2014

Re: How to hookup micro inverters?

With a utility price of $0.129 per kW hour your savings will be in negative numbers as the capital outlay for the GTI system amortized over its lifespan will work out to a multiple of that grid power cost (without any incentives such as tax rebates). This includes panels at $1 per Watt which is about normal now.

A 1kW array will have an average output of about 750 to 800 Watts. Over 3.5 hours that's 2.6kW hours per day, providing all your days are sunny. That's 949 kW hours per year with a lifespan of 20 years (estimated - anything can happen) or 19 megawatt hours. How much will the system cost? Divide that by 19,000 to get the price per kW hour over that time. Or work backwards from the utility cost: 19,000 * 0.129 = $2,448 Can you put it in for less than that?

shift · March 2014

Re: How to hookup micro inverters?

I'm sure i'm could.. but i dont think its quite worth the plunge yet! Thanks for the insight

How to hookup micro inverters?

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