Philip Foster: Practical tips for dealing with black-outs this winter

Posted: November 15, 2015 by tallbloke in Energy, greenblob, Incompetence
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My Thanks to Philip Foster for this timely article on making a simple and effective backup system for coping with black-outs this winter. Be prepared and don’t freeze!

With the likely prospect of power cuts lasting several hours or even days this winter due to becalmed wind turbines, there are things to watch out for and ways to be ready for them.

This article shows how to put in place a standby system in an average home at a cost of around £300.

If you are heated by gas or oil  remember a power cut prevents your boiler from working.  Gas and oil boilers need electricity to run ignition, electronics, pumps and valves. The same is true of most gas cookers. So you will need off-grid electric power.

If you are totally electric then, sadly, there are limited options. It would be sensible to have a camping gas stove (£20-£30), a bottled gas room heater (£130, eg Rhino H02233 Catalytic Heater) and plenty of LED lamps and torches with spare batteries.

  1. If you have a garden and/or a garage,

a petrol generator is the best choice. It can supply a constant 1000w for as long as you have the petrol.

1000w generators (‘inverter’ type which give smooth ‘sine wave’ AC enabling delicate equipment like computers to run safely) are around £250 – £300, such as:

Clarke-ig1000 (made in China)

You can, of course, buy as big a generator as you have room for, but the cost increases proportionally! So I’m using a basic 1000w setup as my example.

You could organise a shared setup with neighbours.

A generator will need basic shelter from the elements, such as an open garage or a simple ‘doghouse’ which allows a free flow of air to ensure the unit doesn’t overheat and the exhaust is fully open to the air.

Important note. DO NOT run the generator in a closed garage or other enclosed space as the accumulation of exhaust fumes is lethal!

[added] You can plug appliances directly into the output of a generator or inverter. Never ever feed the generator or inverter into fixed house wiring, risks electrocution of third parties and other problems.

  1. If not,

then batteries and inverter are the better choice. A 1000w 12v inverter (£110) + large 12v 120Ah Lead Acid battery (£110) + auto mains charger (£30). These can be kept inside.

This setup has limitations as to how long it can run for. It depends on the capacity of the charged battery. For example a 120Ah 12v battery will deliver 1000w for about one hour, 500w for about two hours etc. If you have extra batteries (which are around £110 each) then the setup can last proportionally longer before recharging.

Both systems will run the boiler, fridge, some lighting, FS TV and computer (NOT a laser printer though). [added] if these can be plugged into the generator.

If you have all electric cooking, then purchasing a gas camping stove and a kettle would be strongly advised. They cost around £20-£30 for a double ring.


Here are some power ratings which may be helpful:

Average gas/oil boiler – 250w – pump, valves and ignition etc.

Low energy light bulbs: variable ~ 20w. Even if you don’t like them it is as well to use them during power cuts. LEDs are better than CFs.

Fridge 200-300w, Freezers ditto.

TV ~100w + boxes, about 20w each.

Computer plus extras 200w variable, inkjets are OK but NOT Laser printers.

Home powered telephone units ie wireless type 3-4w.

Mobile phone chargers 10-20w max


check your devices for power use.

If rating is not given in watt then multiply voltage times ampage.

V × I = W

Under no circumstances can you use:

Electric shower, electric cooker, electric kettle, dishwasher, washing machine, hoover, tumble drier, electric heater, iron, hair drier, microwave. Overloading will automatically cause the generator or inverter to cut out.

The National Grid should be able to tell you how long a power cut is likely to last – unless it is caused by storm damage. You can arrange to be rung back by National Grid to tell/text you when power has been restored – look up in Telephone Directory or web – or you can check with neighbours! 


If you feel uncertain about how to do this, talk it over unofficially with a friendly electrician or friend with electrical knowledge. Though the suggested arrangements are quite safe when used correctly, they might not get official H&S approval – but then not dying of hypothermia could perhaps be more important.

You can contact the author if you wish to make suggestions or for advice.

He has successfully put this into practice.

However, please note that the author can accept no liability for the advice given

  1. Scute says:

    Thanx. Just filed it under “Home” and “Global Warming”. Why not laser printers? Do they use a lot of juice?

  2. oldbrew says:

    Volunteer industrial users will be the first to power off (in the UK). Most likely cut-off period due to demand is late afternoon/early evening on weekdays. OTOH breakdowns are obviously random.

    My laptop is using 30W, so 200W seems high even with other devices e.g. router?

  3. tallbloke says:

    Laser printers use a lot of juice intermittently, when charging the drum electrostatically.

    OB: Your laptop? I thought that was steam powered when it came off the ark.

  4. I would be very careful with the suggested system. The lead is a potential death trap – particularly in a power cut, because if someone trips over a lead going from the power source and pulls out the lead, there will be a live bits of metal lying around in the total dark.

    Also, you are creating havoc with the earth. It’s possible the generator case could become live in a fault condition. So basically I’d never have this near young children, any odd leads should be very carefully marked and locked away so no one uses them by mistake, and when in use, the whole thing should be locked away so no one can go near it by mistake (in the dark).

    What would be more sensible would be to have key lights plugged into a 5am socket designed for light use (or even a number of lights). This allows these lights to be removed entirely but I would use an RCD breaker (which requires earthing the generator).

  5. Old brew – just retyping, a 70W inverter works with most laptops – but I have one laptop that overheats one small inverter (plug in type). Router is a light load. Most small screen modern laptops and router will probably work on 70W (but try it and see). 150W will be better.

    However, you’ll need a big car battery sized battery (i’ve run 4 flourescents for around 4hours from a fully charged new caravan battery 70AH? ), so 70W on car battery (30ish AH) should be OK

  6. oldbrew says:

    If you have a car, you have a car battery.

    ‘OB: Your laptop? I thought that was steam powered when it came off the ark.’

    Something wrong with your engineering history there TB 😉

  7. Dave Ward says:

    I strongly recommend against powering central heating from a “modified sine wave” inverter. I found this out the hard way when my central heating programmer got very hot, within minutes. By the time I smelt the “distinctive” aroma, the PCB was well and truly cooked. It transpires that the power supplies used in such devices is of a very basic design, and they don’t like the harmonics present in the output of most of the cheap and readily available types of inverters. The circulating pump won’t particularly mind, but having the programmer (and quite possibly the boiler control circuitry) destroyed isn’t worth the extra cost of a dedicated “pure sine wave” inverter. My system runs quite happily on a 300W continous/600W surge sine wave inverter, but you would need to study the relevant spec sheets to confirm what your particular boiler requires. Circulating pumps normally have the ratings marked on the label, and generally vary from about 40 to 120 watts, depending on the model or selected speed.

    This post mentions the new breed of “Inverter Generators” – so long as you are certain that these do indeed produce a pure sine wave output, they should be fine for running your central heating, but you would probably want to get the house (and any hot water cylinder) well warmed up, and then shut it down for a while. If you have a “Combi” boiler then you’ll have to power it to get hot water, as there is virtually no storage built in. Also note that the induction motors powering fridge & freezer compressors require a much higher start up current than they do when running. This may be a problem with small generators, and you don’t want to have one of these connected at the same time as any other appliances.

  8. catweazle666 says:

    I’ve just bought 10 of these.

    A car battery charger can be readily constructed from an alternator, an old lawnmower engine, some pulleys and a bit of bed iron, Dexion or similar.

    1KW inverters can be had for £50 upwards.

  9. Diesel inverter generators are becoming quite affordable. Anything above 5kVA “prime load” would be a basic requirement for those with electrical appliances drawing lots of juice, even intermittently. You need a small back yard – preferably big enough to put a ventilated acoustic enclosure around the generator’s own as they can be quite noisy (~68dBA @ 7 metres) under load.

    A diesel-powered generator consumes significantly less fuel per kWh generated allowing for longer run-times on a tank of fuel; they can also be refuelled safely while running. The bigger ones with multi-cylinder engines also turn more slowly (engine rpm) so they’ll last longer and tend to be smoother in operation.

    Automatic transfer switches (ATS) are available; ableit costly. As would be the services of an electrician to rewire the incoming grid connection. The ATS automatically starts the generator when the mains supply fails and switches over to generator supply once it’s stable (it can take a minute). When mains supply returns more than intermittently (and regulations permitting), the ATS switchs back to the grid and shuts down the generator after a few minutes of idle.

    The “dead time” in supply isn’t only unavoidable as the generator is likely to be off when there’s a mains failure; the dead time also allows for rotating machinery to stop before supply is returned — which will probbaly be out of phase with the other. The phase synchonisation can be solved technically with inverter generators and “soft” (solid-state) switches between the two supply sides, but regulatory authorities take a long time to catch up because they need to be certain that a supply shut-off is a supply shut-off for maintenance and emergency services.

    A bonus for generator owners is that they can plug their welding machines and heavy compressors into the generators without interfering with the domestic situation.

  10. I suppose that UK may have some different regulations but in Australia gas hot water and gas stoves work without electricity. I have instant gas hot water using bottled gas (cheaper than electric hot water). We have a BBQ running on bottled gas which we have used during power outage. The house has 3 phase power input. During some power outages we have had one circuit with power available while most of the area has had their lights out. We have 3kW (max) of solar (waste of money even though the excess feed in tariff is double the normal cost of power). This is wired to stop feed in when there is a power outage for safety of workers on lines. However, this could be altered to have battery back up but I think it would be a big waste of money – a generator would be better value. A diesel generator would be more reliable. Petrol motors have start problems if not run regularly. The best answer has to be a political solution. Vote out any one that advocates solar or wind or any other so called renewable energy. Take electricity suppliers to court for endangering life if an outage lasts more than a few hours.

  11. oldmanK says:

    Whatever you decide to do, always calculate on appliance in-rush current not the rated wattage. Otherwise you may stall your generator.

    Also minimise electronic control of equipment. A momentary generator voltage dip is equivalent to a program reset (starting a heavy duty grinder next door reset the program of the washing machine).

  12. Ian D says:

    One thing not mentioned and is fairly cheap, is to buy and fit an emergency flourescent light or two, the type that are designed to operate in industry. They can be plugged into a power socket (use a 5 amp fuse) and fixed, in my case near to the electric cooker and also on the stairs. They generally last for a couple of hours when new and recharge automatically from the mains. Then when a power cut happens (in my case last Friday evening at 8 o’clock ish – it lasted for fifteen minutes) lights are available to find the torches.

  13. Suggested strategy.

    Coping with short term power cut (1hr)
    1. Have a wind up torch, where you can find it in total dark or better one that flashes when the mains goes off. Teach the family where it is.
    2. Have batteries and torches for general use
    3. Have an alternative source of heat which does not require electric
    4. Make sure your phones work without power, you have a battery radio, blankets

    Living in luxury in a power cut
    I would aim to get the lights working, then central heating, then fridge/freezer
    My plan is to wait till we start getting the shorter duration power cuts, then to put the lighting circuits on 5amp plug sockets, the central heating & fridge/freezer into a permanently wired extension from their own 13amp sockets at the electric box. So, they key circuits and be unplugged from the mains and plugged into an off grid generator.

  14. Dave Ward says:

    “A car battery charger can be readily constructed from an alternator, an old lawnmower engine, some pulleys and a bit of bed iron, Dexion or similar”

    Indeed it can – However, you will likely have problems getting the engine up to speed, unless you make some alterations to the alternator. The problem (and I found this out by constructing just such a setup), is that as soon as the engine starts, and the alternator cuts in, it draws too much mechanical power for a small engine (I used a 3hp Briggs & Stratton) to accelerate to full speed. The simple answer was to arrange a resistance in the alternator field circuit, which can be switched out once the engine has reached governed speed, and been given time to warm up. In my case a 15 watt car interior light bulb worked fine, with a switch across it to bypass for full output. The Lucas 16/17/18 ACR series (as fitted to older British cars) are ideal, being easily dismantled and modified. The rectifier, regulator and brushes are all separate components, and connected with wire links, so inserting a resistance in one of the brush leads is dead easy. I subsequently developed a fully variable regulator, but that’s beyond the scope of this comment!

    You can’t start the engine without connecting the alternator to the battery first, or you risk destroying the rectifier pack. If you build one of these chargers you will also discover just how inefficient a “claw pole” car alternator is – I found that my 35amp Lucas unit took most of the B&S output, yet I have another identical engine which engine drives an old 230volt AC / 1kw genny quite happily. The charger only produces about 500 watts of electrical power, by comparison.

    Gas cookers with a timer controlled oven need AC power to operate a solenoid valve, even if you never use the timer. The grill and hob burners work directly from the gas supply, but you will need matches or a lighter, if the cooker has mains powered ignition. The worst scenario would be to lose mains power half way through cooking the Sunday roast – the oven shuts down, and unless you can get some power back on to re-open the solenoid your joint won’t be fit for the table!