Thursday, 3 November 2011

Keeping Warm with "FREE" PV Solar Electricity This Winter.

Despite all the gloom generated by a combination of the clocks going back an hour, and the government U turn on Feed in Tariffs, I'm feeling warm and cosy...

Whatever happens to FiT payments we're all guaranteed "FREE" electricity using the  output from our rooftop installation. I have Gas central heating which I will continue to use to warm the house in the mornings and evenings, its the most efficient and cost effective way to heat the whole house.
I've been looking at the options available to make the most efficient use of this power to warm the most used room in my house during daylight hours with a low kWh, high efficiency electric fire

I bought the IGENIX Oscillating Halogen Heater from my local Co-Op for £16.99. It has 3 heat settings, 400, 800 and 1200 kW. I cannot imagine I'll ever use anything but the lowest setting as my 2.66 kWh installation averages 1.1 kWh during the most productive 12:00 - 15:00pm period of the day during the summer months, so winter generation will be closer to the .400W heater option.
Click to view heater details.

The Economics.

I've signed up for the NPower fixed price 'Dual Fuel'  Go Fix 6. It seemed like the best deal at the time, but in reality we're all going to be paying more in the future. I pay 9.37p per kW used, with a daily standing charge of 22p. Based on my previous usage this means I pay approximately 11.2p including the standing charge. 

As I'm going to pay the daily standing charge anyway, I've based the potential cost per hour of using the fire units 400W setting on 9.37p per kWh.

  • If I'm generating NO electricity and I'm using the fire. (.400 X 9.37) = 3.75p per hour to heat the room.

  • If I'm generating 100W of electricity and I'm using the fire. (.300 X 9.37) = 2.81p per hour to heat the room.

  • If I'm generating 200W of  electricity and I'm using the fire. (.200 X 9.37) = 1.87p per hour to heat the room.
Best of all, if I'm generating over 400W's I'm warming the room for nothing...

I'm retired, and at home for a significantly longer than when I was working. Obviously, my circumstances are different to those who come home in the evening and use energy intensively after a hard days work. I have more time than most and can afford the luxury of waiting for appliances to work slowly at lower wattage. 
I'm going to apply the same logic to purchasing other electrical appliances in the future. If an electric kettle or toaster has a smaller heating element and takes longer to finish, I don't care... I'll buy that option in the future.

I'm not representative of the average energy consumer as its reported that they will be paying over £1,300 pa in energy cost in 2011-12. We have a well insulated South facing 3 bed semi detached property in the East Midlands. We've previously used 3618kW of Electricity and 890 units (10,113kW) of Gas each year. 
As our circumstances have altered I think we'll use a little more Gas this year as we're at home more, but less electricity as we're generating our own.

For those of you who are interested, the link takes you to my weekly meter reading spreadsheet.Weekly data.

I'd be very interested if anyone has used low output appliances to utilise their PV output. Let me know how you've got on. 



  1. Another use for autumnal PV: due to donations of surplus apples from fellow allotmenteers with trees, I bought a dehydrator ( and have been drying apples with occasional forays into parsnips, carrots and beetroot and purchased kiwi-fruit, sweet-potato and pineapple: all very fine.

    So I've been getting not just 600W of heat, but 600W of apple- or pineapple-scented heat! (The parsnip and beetroot scent is ... interesting).

    Of course there's usually not enough daylight for a 6-8 hour run, but I'll be starting earlier in the season next year!

  2. When you mention "If an electric kettle or toaster has a smaller heating element and takes longer to finish, I don't care... I'll buy that option in the future" is this a theory of saving electricity? We bought a 3kw kettle some years ago so it boils more quickly than our old one. It uses same ammount of power to boil a minimum amount of water but quickly as a kettle with half the power; the lower energy one would take twice as long. So I guess your point is that whilst in action the kettle will draw some power - albeit briefly - from the grid.

    This is true but the amount is miniscule, I read somewhere that it's not computers, kettles or gizmos that draw significant power, it's the fridge-freezer which can draw 25% of all your electric needs. Fortunately it's low-level albeit constant but I've reduced the temp settings.


  3. @cbatjesmond
    Hi Chris. What a great idea...
    I need to be talking to allotmenteers next late summer to sweet talk them into giving me some of their excess products to dry out.
    It's a shame the internet doesn't provide a "smell" option, my favourite vegetables are parsnip and beetroot.
    Slightly concerned on the economics, but I'm sure the end products more than compensate.

    Best regards.

  4. @Chrisso
    Hi Chrisso.
    I take your point about a high efficiency kettle uses 3kW for a shorter period.

    I'm "Naively" assuming that a 1kW kettle will take 3 times longer, but my installation is more likely to be generating the same amount of power to provide my boiling water for free.

    I'm happy to be proved wrong before I follow this route...

    I thinks Cbatjesmond has the best idea to combat fridge/freezer power usage. Don't freeze the food, dehydrate it during the summer time and store it dried.

    Our ancestors had some interesting ideas...

    Best regards.

  5. @Chrisso
    Soon after getting PV, I also got a 900W (hotel-style) mini-kettle for use when the Sun is out. Apart from not importing power (so losing eco-credibility points ;-) a smaller kettle encourages us to boil what we need, 400ml, 800ml instead of a nearly-full kettle (our big kettle takes nearly 1litre before it registers on the water gauge).

    In other news: the scent of drying strawberries is also v.fine, but I cut them too thin so I'll have to soak them out of the dehydrator :-/

  6. @cbatjesmond
    Great idea. There are only two of us, yet we always seem to have boiled water left in the kettle after filling two cups.
    Amazon are offering a suitable example at £15.49. Check it out.

    Very annoyed yesterday to find a virtual copy of the Igenix electric fire bought recently at £16.99 on sale at "Poundstretcher" for £14.99. Ho-Hum....

  7. @IcarusAmazon are offering a suitable example at £15.49. Check it out.
    That is indeed the very one we have :-) The 0.5l minimum does a 1-person cafetiere, the 0.8l mark does for 2 people. And over 1l (this time of year mainly for waterbottles!) we use the big kettle.