Off the grid

Lithium ion battery

Going off the grid used to be a lovely romantic notion but completely out of the question for the majority of us. It meant, inter alia,

  • Purchasing a huge lead battery pack of at least 10,000 dollars.
  • And, going without power and hot water if there was an extended period of inclement weather.

This page was last updated on 18th August, 2019.


"If an idea does not appear bizarre, there is no hope for it."

- Niels Bohr


By Bernard Preston

The batteries used to be the single most expensive item in your budget if you planned to build a solar farm that was off the grid.

My old pack of 8 lead crystal 200Ah batteries which was moderate in size, but certainly not sufficient to go off the grid, would cost today nearly twice as much as our large 10kW inverter.


That is big enough to heat two ovens, the dishwasher and a pile of small electronic equipment simultaneously, but hopeless once the sun goes down with lead batteries.

They are not only expensive, but they remain relatively fragile. If you discharge them regularly beyond their tolerance one can easily shorten their lives by a half or more.

Redflow and lithium ion are the exceptions but were very expensive until recently; the latter have dropped remarkably in price. 

A large part of the problem is that the new batteries currently being used require relatively modern technology, and nobody really knows how deeply you can discharge them, or how often. Redflow claim you can completely empty them; Lithium ion advocates say 15-30%.

Different sites will proclaim wildly different claims. In the case of my lead crystal batteries, the stats vary by fifty percent, or more.

To my mind, it made no sense to shorten the lives of your expensive lead batteries by a half or more just to save 500 dollars of electricity from the grid per annum.

Solar lens effect

Sometimes circumstances force one to rethink old ideas. I reached that crossroads, confronted with a hopelessly incorrect electricity bill which the authorities would not correct and, in the same week, a power surge from the grid that caused thousands in damage.

Adding to the change of heart is that new lithium batteries that can be cycled far more deeply without damage, and the modern gas geyser that would supply us with hot water on those rare misty days is not out of the question.

Most of our hot water, on sunny days comes from these vacuum tubes; but when it's misty there is very little infrared radiation.

Misty solar day.

We have been cogitating; watch this space.

Off the grid

Off the grid is a much better prospect, of course, if you live in Arizona where there's little cloud cover. Every evening you are assured of a geyser full of hot water, and batteries that are fully charged.

But then you have to pipe in water from some distant source.

For the majority of us, with access to both a municipal water supply and the electrical power grid, it used to make more sense to remain connected, but reduce our consumption of these utilities.


Another consideration is that the inverter itself draws considerable power, whether you are using electricity or not; mine requires about 60 watts just to keep the element activated.

Leaving the inverter switched on all night whilst you are asleep, just to power perhaps three 10 watt flood lights, and the fridge which might come on twice for a short period, would draw in excess of a kilowatt-hour and place a considerable drain on a lead battery pack.

It made more sense to turn it off when we went to bed, and draw a small amount of electricity from the grid.

The purist who wants to be off the grid will see it differently. He is willing to sacrifice his batteries and that's okay; different strokes for all folks. But it was quite an expensive luxury beyond the means of the majority.

For those who live in an area where there is frequent wind, or running water at night, it's another matter; but they are the lucky minority who have other sources of green energy.

But now in 2019 these lithium ion batteries are within the price range of most of you reading this blog; they are no longer impossibly expensive, and have not the slightest problem with staying on all night.

Harvesting rainwater

Rainwater harvesting pipes

Harvesting rainwater from the roof is a simple business involving a network of underground pipes from the gutter downpipes (labelled 1 and 2), leading to a series of tanks or, better still, an underground reservoir. If you're off the grid then you must have battery power to supply the pump. It's not that different to harvesting sunshine and contemplating going off the grid.

Depending on the lie of the land a water tank raised on a tower would provide pressure; it could be filled during the day. We live in a double story home; it would need to be very high.

These underground standard sewage UG110mm pipes collect the water from the down-pipes, delivering the rainwater to a silt trap from which it overflows into a 25,000 litre reservoir.

Rainwater reservoir complete

Harvesting sunlight

Solar power panels 4 x 90W

Harvesting sunlight is becoming more affordable; the price of photovoltaic panels is coming down all the time. Also they are getting larger in size. I have just purchased three new PV panels, 1.5mx1.0m, 305W each.

I'm told that the 260W panels are the most efficient, though I cannot confirm that.

We have now added more panels so that we can go off the grid, to charge these lithium ion batteries.

The old lead batteries remain a backup for a rainy day, but are cycled each day for minor power uses; I may yet get rid of them.

Shadows on PV panels is something else to consider.

Solar generator

Solar generator means connecting the panels to a regulator known as a MPPT, and then to batteries and the inverter; it's a relatively straight forward business. See solar powered generator for more details. Understand this fully before contemplating going off the grid. 

Think hard about the size of the inverter for home before making a start; upgrading costs a lot more in the end. I wish I had gone straight to this 10kW big boy; then it would have hurt only once!

And never go to anything less than a 48V system; the losses in the cabling is much greater at lower voltages.

In short, do it properly the first time. Think, plan, read, talk to people before making a hasty start. Otherwise it hurts many times over.

Whilst in principle I'm very pleased to have upgraded to a 10kW inverter, I'm sorry to say that I'm less than happy with Big Boy, made by MicroCare. Their products have been most satisfactory, and the service fantastic but my experience of this inverter is that it has several shortcomings. I would recommend another brand if you need a very large inverter.

Solar inverter 10kW

Change over switch

A change over switch is vital if you are harvesting sunlight, but also want to remain connected to the utility. You will still need it if you are off the grid, to connect to a generator in times of inclement weather.


There are many different ways of connecting up your electrical supply. I have my own home grown ideas, borne out of several years of experience.

  1. We have circuits that are entirely energised by the inverter, using solar power. When it is switched off at night they cannot be powered up. Our computers for example are supplied entirely from our own electricity; only clean, reliable energy for them.
  2. Then there are circuits that can be energised from either the grid, or the inverter, using a change over switch to toggle back and forth. For example, the electric oven can be powered during the day by the inverter when the sun is strong. At night however, if we use the oven which is rare, it can only be heated by the mains supply.

It is a manual system; if one sees a front approaching, then I can manually change over ahead of time to make sure the batteries are fully charged before the stormy weather arrives.

Fully automated systems also exist; for a price.

Solar power energy

Solar power energy is there to be had, but it does have pit falls. In theory, in the absence of inclement weather, it can enable you to go off the grid.

In short we use less than 5kl of water and less than 600 kWh of electrical power per annum from the grid, but I'm still very pleased we are connected. That's less than most folk use in a month.

Going off the grid would be a pipe dream for us; it would mean investing at least another $5000 in batteries. And we would still have cold showers when a five day mist envelopes our village; it happens several times every year, living on top of an escarpment.

Mains surges

I am have been force to rethink my antipathy towards going off the grid; when you have an unstable voltage from the utility and incompetent technicians doing the maintenance, it can do tremendous damage to your home.

Just imagine this power surge we had recently; it caused huge damage down our street.

Our two new lithium ion batteries cost R90,000 but the inverter had to go back to the factory for new software.

Power surge


  1. Bernard Preston
  2. Solar power energy
  3. Off the grid




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