I posted a week ago to inquire what capacity generator I might need to
power things like central heating, freezer, large american fridge
freezer. The consensus seems to be, go for a 2 kw one, Honda if
I also note that things like inverters can do some of the jobs that a
generator can. Would one be relevant in my case?
Thanks for your help in advance.
I'm not sure why people recommended Honda, they are hideously expensive
for the specification. I'd recommend that you have a look at Kipor
generators which are well built, electronically stabilised and very
quiet for the capacity. Given the price differential you coudl probably
run to a 4 or 6KVA Kipor for the price of a 2KVA Honda.
In brief, no. I use an 800W inverter in a remote barn to provide
lighting only. I've tried to use it for some other applications and it
has burned out a Switched Mode PSU and has difficulty driving difficult
loads. This is because the AC output is modified square wave. Good
enough for lighting and not for much else. A proper sine wave inverter
will cost as much as a generator and you still have to buy sufficient
batteries to supply current and to maintain them between blackouts. I
you really want to have a 2KVA standby from an inverter I suspect you
will be looking at 10x110AH batteries, a 250W solar panel to charge them
with appropriate charging circuit and a 2KVA inverter or a 2VA
inverter/charger. Personally I wouldn't expect to see much change from
In article ,
You would need an unrealistic sized battery to carry the same
energy as a tank of petrol, and you can't easily top it up when
it runs low and you still don't have your mains supply back on.
(The more expensive generators actually use an inverter as the
final stage to generate a good quality output, but that's fed
from the generator, not batteries.)
I've got a 17Ah battery and an inverter. In theory that would
keep my heating alone running for something like 90 minutes if
the inverter is 100% efficient (it's probably not far off, as
it doesn't get hot).
Indeed it could,
A bank of lead acid batteries and an inverter is perfectly capable of
running a whole house for many hours..days even, if you spend the money
Essentially is a very big UPS....;-)
Not sure how big those go, or how many batteries you can hook up to
them. I'd be definitely interested tho.
Could charge on off peak and run the house off it during the day.. ;-)
Almost certainly not. The cost of inverters powerful enough, with a
suitable overhead, to run even modest devices will be great. I have
found that switch on surges mean that at least 50% additional power
handling is needed, depending on the sort of load. And of course you
will need to spend a lot on batteries to store the necessary energy if
the idea is to have more than a few minutes running time, and then find
somewhere to put them. 1kWh = 3.6 MJ. 1amp hour at 12V is 1 x 3600 x 12,
which is 43 kJ (remember ItV from physics?). Thus if my calcs are
correct you need 83 Ah, which might need to be doubled to allow for
inverter inefficiency. That's two meaty batteries for just one
? Not really.
Depends on what you call unrealistic.
You can get a kilowatt hour of battery for about 150 quid..
30 of them would give you enough to power a house for a day, including
things like the odd heater, shower and electric kettle, and be about the
same size as a fridge. About the same (output) energy as a car tankful
Jump leads and your car?
85%-95% is fairly normal on a HF inverter.
Well,. it all depends..
Here is a data point..3500Watts, 5KVA, around £1500...
I am not sure about this particular model, but many others will take
I would think around £6000 might easily get you a 24hr+ electricity
supply, at normal sorts of loads.
With off peak being about 8 times cheaper than on peak, its an
If your quarterly bill is more than around £150, its probably worthwhile..
THEN use a genny set to charge the batteries.. ;-)
If you read down the spec, at full load of 5kW this only provides just
under 10 mins of power. For 24 hours, at say 1 kW load, you would need
about 30 of these beasts. As the tech data says these are for giving
enough time for safe shut-down. Even if you use external batteries the
question of storing enough energy still remains. On a slightly different
issue, I am a great advocate of photovoltaics, but storing enough
electrical energy for overnight remains the major problem.
In article ,
I've never needed it in anger, but my tests showed a standard large car
battery (IIRC 75A/hr) ran mine for 12 hours and still had enough charge to
start the car. Of course it depends on how often the pump runs and things
like motorised valves operate - mine was a pretty basic system with no
In article ,
It makes no sense at all to use batteries for some of these applications.
Far better (and cheaper) to use a portable calor gas etc ring for kettle
boiling - and the same for local heating.
An inverter only really makes sense to run central heating. Even a freezer
is better off run from a small genny.
Oh. it depends on what you want.
I would simply LOVE a system that when its cold and wet and the trees
take out a power line, did not require me to have to fiddle around
starting up motors and rewiring the house..to get the TV and the lights
back on. Cooking we can do on te aga...and having te oil boiler work
would be fine..
AND if it almost paid for itself by using off peak electricity overnight
to charge batteries I ran off during the day, it would be magic.
I was just curious to do the sums on a completely 'battery powered' house.
It is NOT as expensive as I thought..if you can cope with only about 24
hours continuous battery usage.
Obviously if its a mini hurricane and loads of lines are down (as
happened the other year), one expects delays, and goes very economical
on the batteries.
A remote start generator and a changeover switch can make it painless.
Some generators can be configured with an automatic changeover switch
and automatic starting.
The last time I looked at sucha s system is was about £800 for a 6KVA
generator with remote/auto start and £80 for the changeover switch.
That's a lot cheaper than an inverter/battery system.
In an earlier contribution to this discussion,
Anyone know what the efficiency is likely to be of going mains-->battery
In other words, how many kWhs need to go into the charger to get 1kWh out of
As long as the overall efficiency is better than about 50%, you *could* be
better off by buying all your electricity at the off-peak rate and storing
it in batteries - but you'd have a hell of a capital investment (and
probably maintenance/replacement costs) to contend with.