# Power Jack grid tie inverters

• Super Moderators, Administrators Posts: 29,644 admin
Re: Power Jack grid tie inverters

When I do the cost calculations, I also add the cost of the entire installation (including charge controllers, AC inverters, etc...) and assume that batteries have an X year (or YY year for "better batteries") replacement and "budget" a 10 year life for the charge controllers/inverters (may last longer, but not always).

Add that is is (for most people) to actually use 100% of an off grid system's available power (batteries are full, where does the "excess" charging power go) throughout the year (i.e., 66-75% of available power is used on average for a full time occupied off grid home0) also increases the \$\$\$/kWH power costs.

Anyway--I just use those numbers as a starting point to see if an off grid system is practical for the application (and to suggest that conservation is also a very good investment for time and money too). As always, do the detailed design/calculations and figure out "your" \$\$\$/kWH costs (or whatever number(s) make sense to you).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 1,925 ✭✭
Re: Power Jack grid tie inverters

Cost per kWh only make sense when there's a linear depency of cost on number of kWh used. In off-grid system, you generally pay nearly the same regardless of what you use. If you conserve energy, you use less kWh and your price per kWh go up. Only if your system is undersized and every new kWh of usage comes from running a generator, then cost per kWh may make some sense.

If you want to compare to the grid, off-grid system has high "connection fee", small "monthly" fee and very little (or none) cost per kWh.

If electric company says you need to pay \$100K upfrunt, then monthly connection fee, and, on top of this, \$0.10 per kWh, then off grid would have much smaller upfront fees, much smaller connection fee, and almost no cost per kWh.

That said, my off-grid "price per kWh" is around \$0.30. If I lump up the electric company monthly charges with energy charges and divide by the number of kWh used, it's more than \$0.30 (and that doesn't include upfront fees!).
• Super Moderators, Administrators Posts: 29,644 admin
Re: Power Jack grid tie inverters

True, \$\$\$/kWH is a bit artificial... And "all chargers" (i.e., distribution charges, taxes, billing charges, minimum billing, etc.) all need to wrapped together to give a "more real" number for utility charges (depends on your utility).

However, \$\$\$/kWH still gives a good way to compare choices. For example, a desktop computer running 200 watts * 10 hours per day vs a laptop that uses 20 watts:

0.200 kW * 10 hours * 365 days a year * \$1.00 per kWH = \$730 per year power costs (desktop)
0.020 kW * 10 hours * 365 days a year * \$1.00 per kWH = \$73 per year power costs (laptop)

So--The extra \$400 for a laptop computer to do the same work makes a lot of sense (off grid).

If you run the same numbers for on-grid usage at \$0.20 per kWH:

0.200 kW * 10 hours * 365 days a year * \$0.20 per kWH = \$146 per year power costs (desktop)
0.020 kW * 10 hours * 365 days a year * \$0.20 per kWH = \$14.6 per year power costs (laptop)

That extra \$400 laptop premium is going to take a lot longer to recover.

Again--just an example of how to do quick back of the envelope calculations and I why like to give a, very rough, estimate of off grid power costs (including battery/charge controller/inverter replacement costs every ~10 years or so--Batteries may last ~3 to 20+ years, depending on what you purchase).

And, there are those "murdered" battery banks when somebody or some hardware "goofs up"--A small battery bank costs less to replace after those events (not uncommon for the first time off-grid person--although it has been known to happen to experienced folks too).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 1,925 ✭✭
Re: Power Jack grid tie inverters
BB. wrote: »
However, \$\$\$/kWH still gives a good way to compare choices. For example, a desktop computer running 200 watts * 10 hours per day vs a laptop that uses 20 watts

Only on grid, where you literally pay for the kWh used.

Off-grid is different. kWh usage by itself is not a dominant factor anymore.

If you already have a system big enough to run a desktop computer, replacing it with laptop will not bring you any savings.

Moreover, such a huge load as 2kW Air conditioner, if set up to run as a diversion load during summer excess, may cost you less than 2W night light which is on during long winter nights.
• Super Moderators, Administrators Posts: 29,644 admin
Re: Power Jack grid tie inverters

True---But a desktop computer (in this example) is no small load (can be more than 2 refrigerator loads).

Again--I was just showing how somebody can make "monetized" decisions. If the system can support a new desktop computer--then is possibly started out over sized.

I suggest 3.3 kWH per day (100 kWH per month) is a fair sized off grid system for a small energy efficient home... Throwing a desktop computer used 10+ hours per day can almost double the power usage.

In the end, power usage is a highly personal choice... I am not trying to suggest a "moral" or "green" way of living one's life--Just some different tools to help make those decisions.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 1,925 ✭✭
Re: Power Jack grid tie inverters
BB. wrote: »
I suggest 3.3 kWH per day (100 kWH per month) is a fair sized off grid system for a small energy efficient home... Throwing a desktop computer used 10+ hours per day can almost double the power usage.

There's another aspect to it. The smaller the system, the higher the cost of kWh it is capable of producing. Therefore, people who have larger system will have lower "per Kwh" cost and it is easier for them to beat the grid pricing.
• Solar Expert Posts: 1,973 ✭✭✭
Re: Power Jack grid tie inverters
NorthGuy wrote: »
There's another aspect to it. The smaller the system, the higher the cost of kWh it is capable of producing. Therefore, people who have larger system will have lower "per Kwh" cost and it is easier for them to beat the grid pricing.
By the same token, someone who buys too large a system for their needs will likewise be paying more per kWh than someone whose system size is well matched to their usage.
• Solar Expert Posts: 1,925 ✭✭
Re: Power Jack grid tie inverters
ggunn wrote: »
By the same token, someone who buys too large a system for their needs will likewise be paying more per kWh than someone whose system size is well matched to their usage.

Sizing is everything. Whether you build it too small or too big, you will end up paying more. Easier said than done

The huge advantage of the grid is that you need to size anything except main breaker, which is easy to re-size.
• Solar Expert Posts: 413 ✭✭
Re: Power Jack grid tie inverters

That's why I replaced my old non Energy Star rated fridge with one that was and sold the old one. My current fridge draws about 130 watts on a 45 to 50% duty cycle. The old one was MUCH higher. The Energy Star "rating" was around 475kWh per year, but I set it colder than "economy" because I used to have two teenagers living here. The old one was something like 1,200kWh per year.
• Solar Expert Posts: 1,925 ✭✭
Re: Power Jack grid tie inverters
tallgirl wrote: »
That's why I replaced my old non Energy Star rated fridge with one that was and sold the old one. My current fridge draws about 130 watts on a 45 to 50% duty cycle. The old one was MUCH higher. The Energy Star "rating" was around 475kWh per year, but I set it colder than "economy" because I used to have two teenagers living here. The old one was something like 1,200kWh per year.

Yep. I bought a new efficient fridge. It is twice as big as the old one (30 years old), but consumes only about 1/2 of what the old did.
• Solar Expert Posts: 413 ✭✭
Re: Power Jack grid tie inverters
NorthGuy wrote: »
Yep. I bought a new efficient fridge. It is twice as big as the old one (30 years old), but consumes only about 1/2 of what the old did.

I wanted the one I bought because it has "French Doors" and will hold just about anything. My old fridge was a side-by-side and it was a tight squeeze for many larger items. That it sips electricity is an added bonus.
• Solar Expert Posts: 50 ✭✭✭✭
Re: Power Jack grid tie inverters

A German engineer has invented a plug in the wall system and the European code officials are now in talks to create EU standards for the product. The plug into the wall receptacle, spin your meter backwards, mini power plant is currently being sold worldwide in about 20 different countries.
• Banned Posts: 17,615 ✭✭
Re: Power Jack grid tie inverters
A German engineer has invented a plug in the wall system and the European code officials are now in talks to create EU standards for the product. The plug into the wall receptacle, spin your meter backwards, mini power plant is currently being sold worldwide in about 20 different countries.

Plug-n-play is legally sold in the US and Canada too; it just isn't legal to install.

Whereas it will be interesting to see what sort of "standards" "European code officials" come up with, methinks this is more deceptive pie-in-the sky marketing lies by the companies trying to trick people into buying their garbage.
• Solar Expert Posts: 1,973 ✭✭✭
Re: Power Jack grid tie inverters
A German engineer has invented a plug in the wall system and the European code officials are now in talks to create EU standards for the product. The plug into the wall receptacle, spin your meter backwards, mini power plant is currently being sold worldwide in about 20 different countries.
Let's see... to spin your meter backwards it would have to inject more power into the wall receptacle on a single circuit than your whole house is pulling from the utility. You might as well go ahead and call the fire department before you turn it on so they will get there sooner.
• Banned Posts: 17,615 ✭✭
Re: Power Jack grid tie inverters
ggunn wrote: »
Let's see... to spin your meter backwards it would have to inject more power into the wall receptacle on a single circuit than your whole house is pulling from the utility. You might as well go ahead and call the fire department before you turn it on so they will get there sooner.

Nah; you just shut off everything in the house and the 1800 Watt single-line feed will spin the meter backwards.

It's not very reputable of a company to promote any product before it is certified for use. Akin to "our cold fusion generator is just around the corner! Invest now!" :roll:
• Solar Expert Posts: 50 ✭✭✭✭
Re: Power Jack grid tie inverters

the German engineer that invented their version just published this: "Overloading the circuit through the use of plug & save is not possible for adherence to simple rules of conduct (E.g. Exchange of a 16 ampere fuse with a 10-amp fuse). Several hundred tests of the Sun invention Development Center have shown that. In addition, several thousand plants in Germany without problems - even the 1st generation plants. " they have distributorships in dozens of countries worldwide now. It will be interesting to see how this plays out,especially since the European regulators are now involved in making standards for this product. Let's see how this affects US markets.
• Banned Posts: 17,615 ✭✭
Re: Power Jack grid tie inverters

Here we go again.

One 200 Watt plug-n-play micro inverter is not going to overload the circuit.
The problem comes when people like how the first one works and decide to expand. So they plug a couple of power strips into the (dedicated) duplex 120 VAC outlet and connect a combination of twelve 200 Watt micro inverters and/or other loads because its all the same kind of plug.

That's the whole problem.

Connect 1800 Watts of inverter to one end of a 15 Amp service line and put all the loads on in between that and the service panel, it works. Get it out of order and you can have 30 Amps of current traveling down 14 AWG wire wire that can only handle 20 Amps max.

For the last time: these things are not safe and can never be made so due to the very nature of their method of connection. It is just too easy for people to change the install from safe to not safe by re-arranging plugs.

It's bad enough any idiot with a screwdriver can take apart "hard wiring" and re-arrange it to be unsafe. You don't need to make it easy for them.
• Solar Expert Posts: 3,123 ✭✭✭✭
Re: Power Jack grid tie inverters
Nah; you just shut off everything in the house and the 1800 Watt single-line feed will spin the meter backwards.

It's not very reputable of a company to promote any product before it is certified for use. Akin to "our cold fusion generator is just around the corner! Invest now!" :roll:

And, as we have seen already, it is legal in most countries to sell products which are not (and may never be) certified.
Selling electrical devices in the US which are not UL approved may be policed by CPSC on import, but not by NEC or local codes until you try to actually use them.
SMA SB 3000, old BP panels.
• Solar Expert Posts: 3,123 ✭✭✭✭
Re: Power Jack grid tie inverters
the German engineer that invented their version just published this: "Overloading the circuit through the use of plug & save is not possible for adherence to simple rules of conduct (E.g. Exchange of a 16 ampere fuse with a 10-amp fuse).
However, in NEC-land, you cannot have a breaker smaller that 15 amps on a residential receptacle circuit (other than dedicated) and you will not find smaller breakers for residential panels anyway, so the suggestion is not applicable.
And, as stated earlier, the rules of conduct would also have to cover not plugging in more than one of the devices on a circuit.
SMA SB 3000, old BP panels.