I response to my other threads here's an outline of our off-grid power
A couple of years ago now I asked some questions here about the costs of
running diesel generators for domestic power. Some of the numbers I
got back almost put me off buying the house, but I, with my partner, did
buy the place.
The power set-up as we bought it comprised three diesel generators, all
Listers of different power outputs, 1.75kVA, 3.5kVA and 11kVA. This
system had evolved over the years.
Historical side note: We have recently made contact with the, now, 94
year old woman who lived in the house from the 30s through to the 70s.
She and her husband put in the two lower powered Listers. She, in fact,
poured the concrete floors we still have today. Perhaps I should get her
back to do the tower foundations!
The house could run directly from any of the generators, the choice of
generator was based on what you wanted to do. The lowest was fine for TV
etc., the next for a washing machine, the largest was put in by later
owners to run a blacksmith's forge.
The generators were used only when needed, evenings, weekends. Thus we
don't use a video, say, and we have a gas (lpg) fridge---came with the
In addition to the diesel system the previous owners added a couple on
small wind turbines (one 50W, one 400W) on the gables of an
outbuilding., and a couple of small battery banks with a 600W inverter.
This system allowed for lights being used in the middle of the night but
not much more.
The whole system is very ad hoc with lots of switches being used
depending on what you need to use. So, we decided last year to look at a
more modern system or going on the grid.
Going on the grid would cost around 20K. We quickly realised we could
spend a lot less than that and have a system based on solar and wind
power. We then had to decide whether to go the DIY route or get a
supplier fitted system. Luckily we have a company that does renewable
systems just a few miles away, which makes for good service. Their quote
for a full system was about 15K but as it is an 'approved' system we can
get 3-4K of grants to cover some of that.
The DIY route would get any grants and the kit would attract 17.5% VAT
instead of the 5% we paid. However, there's probably not much in it in
terms of the hardware costs after the sums.
The system we went for, based on our location and needs, comprises 6
110W Solar PV panels, one Whisper H40 (900W) windcharger, a very clever
3.3kW inverter and a bank of 16 6V deep-cycle batteries. In addition
there's a solar controller and a wind controller in there. The inverter
is also wired to the 11kVA Lister as its back-up charger. It can also
patch us straight through to the genset if we use very heavy loads.
All the wiring has been done by the company we got in but the
groundworks and preparations are DIY.
The first stage was just the inverter, batteries and genset wiring. This
immediately made a tremendous difference as the genny was turned on
just for charging for 2.5 hours every 3 to 5 days.
The solar was added next, on the shortest day of all days! We have been
surprised at its effect. Even at this time of year it is delaying the
need for diesel charging by a few days. The last few days have had
record daily inputs of over 60Ah. This is more than enough to cover our
normal nightly demand.
The final part is the wind turbine. The charger we have chosen is
designed to work in high wind areas and has been used in similar
locations to ours (exposed!) in the north of England. We are predicting
that the diesel generator will be used very little once the turbine is
up and running. In fact we may have to make a decision as to whether to
divert its dump load to some use other than heating the inverter
shed---possibly to a secondary immersion heater.
We then have to decided what to do with the old system. The Air 303 did
suffer some damage in recent storms and an electrical storm fried out
600W inverter. The new inverter is protected from this and the new
turbine is better suited to our conditions and will be better installed,
though obviously there are no guarantees.
We still feel we need to hang on to the 3.5kVA genset as we like the
idea of backup systems. We will probably try to sell the smallest
generator, it was built in 1960 so it may be of interest to a collector.
We may used the older wind/battery system to run a DC lighting circuit
for the outbuildings with a small inverter there for emergencies.
In fact this raises a final question about the recently discussed
regulations on electrical work. Does it apply to a situations such as
mine on the other side of the 'meter'? We don't actually have a meter
but how does it apply to the old inverter system itself?