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More then just FAQ

Heres a page I finanlly got around to writing. I should have done it ages ago, after all this is what we are attempting to do with this site i.e. answer questions about life with alternative power.


Q: What is P.V.?

A: Photo Voltaics are those devices that produce electricity when exposed to light. Commonly known as solar panels and often confused with solar hot water panels but they are very different.

Q: How much to power an average 3 bedroom house?

A: I don’t know! What is an average house?

What are you going to put in the house? Are you happy with an Ipod or do you need a full surround sound system with massive plasma screen or most likely something in between? Do you stay up all night or go to bed at dusk? How much refrigeration do you require? Are you vegetarian or king of the BBQ? (Freezer requirements).  Is hydro a possibility or is solar the only option?

People and their habits are as different as their houses, cars, boats, clothes, attitudes and power systems. For me to be happy with the amount of power from a system I think I would need to spend in the region of $30k in components or so. (2009) the good news is some components are getting cheaper as time goes on. See below to get an idea of what we run and our habits. You may be very happy with way less (I have many customers who are) or you may want a great deal more. Either way lets talk as that’s the only way we will both find out :-)

Q: What can I run on an alternative power system?

A: This depends on the system size.

On a system designed for say 3 or more kilo Watt hours (kWhrs)output per day you will be able to run most appliances found in a grid powered house.

Our house for example has; 

  • Large chest freezer 
  • Standard size fridge
  • TV 
  • Sky 
  • Stereo (normal) :-)
  • Desktop computer (a laptop would draw less) 
  • Lights of course 
  • Espresso machine - well thrashed 
  • Vacuum cleaner
  • Power tools
  • washing machine
  • compressor (run off generator)
  • Kitchen appliances toaster, blender, mixer
    (We have given up and use an electric toaster because those ones you put over the gas flame usually sets off the smoke alarm around here)
  • Me and mine also want a dishwasher in the future.

At the moment we are drawing about 2.5kWhr per day this will be updated as I have not been collecting this data long. Consider the average on grid kiwi house is in the region of 20kWhr+ a day and it shows what can be done. Remember we purchase more energy in the form of LPG and diesel but this will be reduced in the future with solar hot water and more solar PV

Cooking is on gas, woodstove & small electric oven run off genset for the odd pizza or cake in summer. Hot water is via gas calafont and hopefully solar in future. Our system does not have enough solar (still in the boxes waiting to be put up) and we run a generator far too much for my liking (600hrs/pa). Bigger batteries once these ones need replacing (535Ahr) will also be an improvement.

Q: Can I run my Jimmy Hendrix model sound system at full power on my alt power system?

A: if your system is large enough, within reason, generally the neighbours are going to be a bigger problem. Seriously though stereo systems generally don’t really draw a great deal, even in party mode, and are fine. If Metallica are doing a gig at your place you might need to hire a genset for the event. While on the subject of noise levels remember your neighbours when considering generator options as well.

Q: Can I run a heat-pump/Air-conditioner on alternative power?

A: While it is true that heat pumps are very efficient compared to other forms of electrical heating they draw too much to be powered by renewable energy systems that most could practically afford. A generator would be required in most instances and this would be really inefficient use of the diesel if the heat pump was being used to heat. Better to use the diesel in a furnace. If air conditioning is required for cooling then a generator may be your only option. It would be far better to design the building with passive cooling and another form of space heating such as passive solar and a wood fire. 

Q: What maintenance is required on an off grid system?

A: Depends on the system.

Solar, occasional cleaning of the panels may be necessary

If the system incorporates a generator then all the usual stuff associated with engines

Generators tend to be the most problematical part of off grid systems.

Wind turbines, I would recommend checking the rigging before (if possible) and after a big blow. Turbine should be lowered say every two years (yearly in coastal locations) for inspection of rigging and machine, some benefit from a shot of grease in the furling mechanism if applicable. 

Hydro turbines need their intakes cleaned, nozzles may need unblocking, penstocks should be inspected from time to time, and some I have worked on require the runner shaft bearings to be greased. Silt/rocks may need removing from the intake pond. 

All systems utilising batteries need to have the battery electrolyte levels checked, specific gravities checked, terminations greased from time to time. Exceptions are AGM and GEL cells where only terminations can be checked as the cells are sealed, but these are expensive for reasonable sized systems and most opt for flooded cells. Other than that dust the electronics occasionally, look at the metering daily (becomes a habit anyway) and marvel at how in tune you have become with the weather, seasons and Mother Nature in general 

Q: What is S.G.??????

A: Specific Gravity a complicated sounding term for a simple concept.

1 litre of pure water weighs 1 kilogram (kg) Electrolyte from a fully charged battery will weigh the region of 1.225-1.300kg/litre depending on the type of battery, type of use etc etc. (A reputable dealer will advise what the SG for your type of battery should be) This is due to the electrolyte in a healthy battery being a mix of pure water and sulphuric acid. This solution is heavier or denser for a given volume than just water alone.

It is not necessary to draw out a litre of electrolyte and measure with the kitchen scales

Specific Gravity is measured with a Hydrometer.

A hydrometer is simply a float with graduations on it. Due to the density of the battery electrolyte being greater/heavier than that of water the hydrometer will float higher in battery electrolyte from a battery in good condition than it will in water. The amount of extra buoyancy the float has can then be read off the scale to determine the batteries condition.  

Your battery supplier should advise you on safe working practices (battery acid is harmful to eyes and skin) and demonstrate the use of the hydrometer.

Q: What advantages are there in paying a professional to design and install my alternative power system?

A: My Advice & Opinion. Installation by a registered electrician so that it is safe! And so that it works!! Some installation work can be done by customers; there is still plenty of room for some DIY to save on costs even with a professional install. Electrical work can perhaps be done by a local or relative sparky if it looks like this may be more cost effective. There are aspects of an off grid systems that most electrical workers will not be familiar with and a designer should liaise at the very least I think.  

Design and supply should be done by a reputable dealer in the industry that knows what works with what and knows the appropriate standards to work to. While it is true there are many systems out there that have been successfully cobbled together by their owners, they are in my experience, in the minority to the unsafe and unreliable systems out there.

There are some that I would not of slept in the house with in until some modifications were made. I am happy to demonstrate how even a small battery is quite capable of burning down a house. Just because its low voltage doesn’t make it safe, and the output voltage of the smallest inverter is still 200 volts or more and still potentially lethal.

The design and installation costs rarely exceed say 15% of the overall system cost anyway and warrantee issues, should they arise, are much more likely to be dealt with in a satisfactory manner by a reputable dealer than the person on the cyberspace marketplace who has conveniently disappeared.

Q: What is an Amp Hour (Amp/Hr?)

A:The Amp hour is a unit used in the battery industry to define the capacity of a battery

It’s a bit like the capacity of a water tank in litres, or maybe gallons if you’re over 40 or so :-)

This unit is also used to describe the state of charge (SOC) of a battery. For example

If we have a 100 A/Hr battery and we use 5 amps for 3 hours we will have used 15A/Hrs

And the battery will be this many (15) A/Hrs from full charge. To bring the battery back up to full charge a solar panel array supplying 10 Amps will need 1.5 hours of full sun to recharge the battery. In practice it takes even longer because of

  • Losses within the battery itself
  • The fact that as the battery reaches full charge the current has to be tapered off so maximum voltage for the battery is not exceeded. This is the tricky bit  that our solar regulator or charge controller does for us automatically


Q: What’s it like living on free renewable alternative power?

A: GREAT. You do not need to be some sort of martyr sitting in the dark living on mung beans to be on alternative power. However it’s anything but free. Lets be real about this, the quality gear isn’t cheap. Batteries do wear out and this is where good design, installation, and setting of parameters comes in to get the maximum life Mine are 8 years old and still going well (2009) but we are mindful that they will need replacing eventually.

Generators cost time, money, and travel to fuel and maintain, and here at home, are generally a pain. They are however, a necessary evil to rescue batteries in periods of bad weather or extended system use. Even "deep cycle" lead acid batteries respond badly to been left discharged for long periods. (See below) A well set up power system may only require a small petrol machine for a few hours a year (about 4kW up is a good size) and some people just hire them. If you have large requirements for power at certain times

E.g. Commercial workshop (hand held power tools are not generally an issue) or large influxes of guests, a bigger diesel machine may be worth considering. If auto start from the system is required I definitely would advise a diesel

Wind and hydro turbines are mechanical devices and need maintenance like all things that move and will eventually, like a car or generator etc wear out. (Mainland Hydros are legendary for their longevity and will outlast the even the best wind-turbines I think)

How long equipment lasts is usually directly proportional to how much you paid for it.

Solar panels are an energy source that you pay for up front and that should provide power for 25-40-who knows how many years if they are quality product, and in my opinion the most reliable, silent, hassle free, green way to generate power. Trick is to have enough of them and install correctly.

Unlike the grid which is limited only by your ability to pay the bill, the amount of power you have at hand in an alternative power system is limited by the size of the system. If well designed to your accurate brief this will be sufficient. A friend recently commented it’s a bit like living with tank water. If you have enough roof area to fill an appropriately sized tank, you turn the tap off when finished and practice a bit of conservation you’ll be fine.

It becomes second nature very quickly.

The only difference in a solar powered house is you usually won’t find the TV and other bits on standby as these are like leaky taps. Sensible folks don’t tolerate it with water so why tolerate it with electricity? I guess because you can’t hear it dripping?

Q: Should I run my deep cycle batteries dead flat like the one in my cell phone?

A: NO.... NEVER   EVER !!!!!

"Deep cycle" I think, is entirely the wrong name for the kinds of batteries we usually find in off grid systems but this is how the industry has named them to distinguish them from cranking batteries like the one in your vehicle (which are designed for rapid discharge & recharge). "Long slow discharge battery" might be a better term technically but I guess it doesn't have the same marketing zing.

"Deep Cycle" batteries will last longer with many short shallow cycles than they will with a lesser amount of really deep cycles -go figure! This is another important aspect of system design. A battery deeply discharged should be charged as soon as possible to avoid a condition known as sulphation. Some times this condition is more commonly known as stuffed ...or worse, like broken, and can lead to tears (Two things genuine deep cycle batteries have in common is that they are all expensive and heavy!) Sulphated batteries can sometimes be resurrected but it's a hard energy intensive expensive road and is definitely best avoided.

More will be added here as I think of it or as people ask me more great questions. Feel free to email us with yours:




  Here is a friends approach to space heating Wet back on the wood range provides the hot water to this automotive radiator, 3 speed warehouse fan cable tied to back moves the air. Cheap and easy approach. There is no reason why it can't be done in a less "rustic" manner :-)  


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The Watt Shop - Alternative Power  |   PO Box 342, Kaeo, Northland, New Zealand  |   Phone 021 784 678

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