[nicandem]

Now that the tariff has been reduced to not a lot (especially if in an old house and you don't like double glazed, central heated, dry air properties is it worth getting PV?


...without taking into account the tariff, how much do people save on their bills?


trying to work out viability on PV (3kw system) and solar water.




any info appreciated


Nic

[Dan]

We've got a 4kW PV array. On a good sunny day (east coast of Scotland) it will generate 25+ kWh. Over the course of a year it will generate between 2500-3500 kWh, or units of electricity, the UK average per kW is apparently around 700-900 kWh per year.

Electricity at the moment is about 14p per kWh to buy.

So your 3kW PV system, assuming a conservative annual output of 800kWh per year per kW, will generate 2,400 kWh per year, or £336 worth of electricity. Offset the feed in tariff (16p now, I think?) and account for the capital cost, and you can judge whether it's worth it.

You can be almost certain the cost of electricity is going to rise over the years, and the FIT is index linked, so the margins should get better as time passes.

Can't comment on solar water. We've got a ground source heat pump and it couples really nicely with the PV.

HTH.

[nicandem]

thanks for that... got to hink about it, fit is only 7.1p so will take about 10 years to recoup

[mab]

Another thing to think about is that PV is so cheap now, that it may be better to get another Kw of PV (i.e. get the max 4kw) and use a timer to dump the excess power into the immersion heater.

It may seem a bit wrong to use PV to heat water but it doesn't cost anything to use the excess power generated during the day - and the extra Kw of PV will cost much less to install than a solar thermal installation and doesn't require major plumbing modifications. Although to get the best out of such a system you'd probably want a large, well insulated hot water tank/thermal store to 'stock up' on hot water.

The only problem is that I'm not sure that there's an automatic switch on the market that will determine if you're generating enough power to use the I/H, so you may have to do this manually. Someone I know has a tank with two I/Hs; a 3Kw and a 1Kw and he uses the 1Kw if it's not a bright day.

Do the sums and you will likely find that it's cheaper this way.

marcus

[deepinthewoods]

theres alot you can do to improve your windows to increase the insulation, without being double glazed, ive had some really good results insulating 200yr old sash windows with thermo glass.

[nicandem]

im having the windows revamped...getting rid of rotten bits and draught proofing
I work outside most of the time, am into wildfowling, riding motorbikes and camp throughout year....
therefore most houses are too warm... lived in last one with windows open probably 360 days per year


also just picked up everhot stove so house is getting warmer this winter :-)

[northfifeduckling]

Scottish Power halved from what they charged us before. It's guesswork so far as they said that at night we use theirs and at daytime they pay us for ours....will have to wait for the next meter reading to be more exact - but it's winter...

[kingnigel]

ours has been in for just over 1 year, its 3.75kw system, facing south out bill was £90/month it is now £33/month and we are still over paying by a few quid in winter, i think it will drop further in summer. i calculated our use last summer and our bill should have been £15/month but they keep it high thinking winter will be loads higher.  might be hard to work out next year as im looking at installing a 2kw wind turbine next, ive bought one but havnt even checked planning permission or anything else yet (it was going cheap so i went for it. lol)

[Small Farmer]

We have just under 4kw facing east and south.
Installed in March 2011 we got 3700 kwh in ten months of 2011 and 3350 in 12 months of 2012.  I think the predicted production was 3500.