Grid tie conversion to off-Grid

It does depend on how far you want to go... However, in general, it is not usually cost effective to convert from Grid Tied to Off Grid/Hybrid power... More or less, when you include batteries (and battery replacement) and extra hardware (battery chargers, AC off grid/hybrid inverters, and replacing those every ~10+ years)--Your average kWH cost can easily run in the $1.00 to $2.00+ per kWH (there are a couple people here that have gotten their kWH costs down towards $0.50 to $0.40 per kWH for full time off grid--But that is usually in a more sunny region--Assuming you are in New Jersey/North East?).

When Grid Tie system subsides "go away" (has gone away in Hawaii and Nevada, and some other locations)--Solar becomes difficult justify. In general, off grid solar power (battery based) is (roughly) ~4x more expensive than grid power in the US.

Off grid power makes sense for 1-10kWH per day type systems (30-300 kWH per month)--For larger systems (i.e., if you are using 50-100 kWH per day?), you are talking about some really large and expensive systems.

-Bill

Ruben,

With grid tied systems--They act for all the world like a giant AC Battery bank (your system is "recharging" the grid) and you have an "agreement" with the utility company on how they charge you for feeding energy backwards into the grid (from paying you retail pricing, to wholesale pricing, to taxing you for having solar panels like Spain, to making it completely illegal).

The reality is that you have roughly 6 hours +/- to gather solar energy and 24 hours in a day to use it. Your choices are:

• Large array and store excess energy in a battery bank for use during off-sun hours
• Large array and "do work" during the day (pumping water into a storage tank, run washing machine, pre-cooling water into ice and use melting ice to cool home/work off sun, etc.).
• Smaller array to just power your loads when the sun is up.
• Forget full solar and instead invest in energy conservation (LED lighting, newer/high efficiency heat pump systems, laptop vs desktop computers, etc.).

Perhaps in the next few years, you will start to see high(er) performance LiFePO4 batteries (or similar) vs Lead Acid. The newer battery technologies can offer many advantages over lead acid batteries (faster charging/discharging, longer cycle life, no "aging" effects when stored at partial charging, etc.)--But right now, higher costs, more complexity (per cell balancing/protection against over/under charging) make Lithium batteries more cutting edge. There are some other battery chemistries that also may be cost competitive in the future too--But good quality lead acid deep cycle batteries are still (for the most part) the best price/performance at this time.

If your power needs are relatively modest (1,000 to 3,300 WH per day or 1-3.3 kWH per day)--You can build an off grid system for less money that can, somewhat, provide cost effective alternative to utility power+backup genset (if you have afternoon blackouts).

I always suggest doing paper designs of your system options first--They do not have to be 100% accurate, but can give you an idea of what the costs and design issues/options are--And see if it is even worth your money to build out such a system.

There are ways to connect Grid Tied AC inverters to a PSW/TSW (Pure/True Sine Wave) AC inverter + battery bank--And actually feed energy "backwards" through the off grid AC inverter and charge the battery bank (obviously there are details to discuss)--But it does not really do much more than a standard off grid/hybrid AC inverter system does (forgetting the GT inverters).

-Bill