Solar Panels - Are they worth it?

Cardew

raider wrote: »

Funnily enough, I've just been going through my bill for the last quarter and using a spreadsheet comparing it to using two previous bills of Q2.

2009 Q2 = Ave 12.81 kWh per day
2010 Q2 = Ave 11.53 kWh per day
Combined Q2 Ave = 12.17 kWh per day

With solar installed 2011 Q2 = 6.47 kWh per day.

12.17 kWh - 6.47 kWh = 5.7 kWh saved per day X 91 days = 518.7 kWh saved.

518.7 kWh X 13.15p (unit rate) = £68.21

Not to difficult

Unfortunately, as pointed out above, that is exactly the way most 'claims' of savings are made.

People fit 'fuel economisers' to their car - which consists of a simple magnet, and claim it reduces their fuel consumption by 30% and produce figures that to their mind proves the point!

The EST have come up with an estimate that on average people use 25% of their generated electricity in the house and save £70.

The only way to know how much you have used is to have an export meter fitted(which is why I said it wasn't easy to know how much you have saved)

The EST reached their figure of 25% by monitoring systems. Several people who post on MSE have export meters and their findings support the £70pa figure.

raider

zeupater wrote: »

Hi Raider

I think that the point being made was that you wouldn't know what proportion of the energy saving would be directly related to the pv generation as opposed to savings due to other energy reduction activities which awareness of generation and usage bring about.

If you were using an average of over 12kWh per day in Q2 for the last couple of years then there was definately scope for improvement anyway, mine was reduced gradually from ~14kWh/day in Q1/Q2 2006 to ~7kWh/day before installing pv. This is where many see savings after installing pv which could have been made even without having pv.

I can quite confidently claim that the majority of the reduction in our purchased energy is as a direct result of having pv, however, having purchased further energy saving equipment such as a LED TV, even I can't claim to know what the saving directly related to out pv installation is, but I can say that we now average around 3kWh/day, with somewhere around 3kWh of the ~4kWh/day energy reduction being due to pv.

Another point relates to the 13.15p/kWh cost of electricity, is this your tier 2 tariff or an average cost ? .... At an average of 6.47kWh/day you will only ever be saving energy at the tier 2 rate ... my tier 2 rate for the next 12 months will be just over 10p/kWh(inc VAT) before incentives .....

HTH
Z

Hi zeupater

I agree with you on the point about extra efficiency savings due to awareness of having pv installed. But at the same time I would guess most people venturing down the route of pv to have made most efficiency savings previously (that was my case anyway)

My 12kWh a day is primarily due to being at home every day, with a tv, pc running all day and cooking on an electric hob. Still scope for improvement I guess.

Just realized I got my own figures wrong on the unit rate , was looking at the standing charge. Should have been 12.372p, thus saving only £64.17. This was EDF's standard rate (non tiered), now on a fixed non tiered at 8.5p.