So was August a  good month for Solar PV ?

Short answer is yes !
The total haul was 445 kWh or 3.6 kWh per day per kWp installed on Glasgow SW 30 degree roof.

Commenting on the August results.

  • Highest Daily record now 25 kWh
  • also a new record low of 4 kWh as well !
  • Financial contribution £222 (FITS, used, exported ~ 50p kWh)

Here is some additional snaps of relative electrical household usage and Net metering.

…..and finally how does it compare to the official prediction /statistics ?

Answer: rather well for August, actually spot on for a July, but it’s all down to the weather !


The way google conducts itself is so different to the razzamatazz of Apple with its product staged releases.  Take the Google Power Meter after an initial video then foggy release I have found it to keep getting better without any hint, notification or even documentation.

On first use I had a number of bug bears, product suggestion ideas and annoyances.  But they just secretly get slipped in, like some new game you have to spot them.

One feature lacked on release way the ability to wave the mouse over the google flash chart and see point values, quite annoying.  Anyway, it’s slipped in unannounced and without any update/install/selection.  Can’t even see a mention of it when searching the web.

Keep it coming.

Running mobile phones for a family of 5 can be a costly affair.

Or maybe not, here’s the challenge.

  • Target Cost £5 per person per month.
  • Unlimited free calls between all family members.
  • Unlimited SMS/texts for 2 teenagers
  • Some inclusive talk/texts for everyone
  • A basic phone

It was a rhetorical question, because it can be done !

Check out here’s the deal.

  • Free calls between all giffgaff’ers no need to register or pay for family/friends
    (need to top up £10 every 3 months = 10 x 4 x 5 = £200 )
  • Unlimited Text goodie bag for two teenagers = 5 x 2 x 12 = £120
  • Giffgaff referral payback for family (should be more)
    £5 referrer and £5 for reciever, that gets 4 x 2 x £5 = -£40
  • Miser grade 5 phones at 90p each = £4.50
  • Calls are 8p/min, texts are 4p so you get some minutes included

Total annual cost = 200 + 120 – 40 +4.50 = £284.50 /5

= £ 4.74 each per month !

Another key benefit is that is contract free, no lock in. Hurrah

What’s the downside ?

Not much, but you don’t get an iPhone though !

Anyone who knows me, call and I’ll sent a free sim.
You get a £5 added to your account for nought !

Even with the days shortening we had a super sunshine Sunday and this was backed up by generating the highest total to date since our July installation.  Whilst the daily energy was 25 kWh, I looked at the maximum Wp reading and was surprised to see that the maximum peak was only 3.25 kW.

Head scratching begins to figure out why the peak was down over 18% on less spectacular days.  The inverter was up at 60 oC but this is not an issue.  The panels were rather hot.  I’d hazard from the touch test maybe up nearer 60 oC as well.

Apparently, according to a source on the web …..
Crystalline panels suffer a high voltage DROP when heated by the sun (Crystalline panels lose power, for each degree above 25C). At the 60 C they lose approximately 30% power. Output only 60% to 70% of Wp.
.This was from an article pushing different materials.
Other sources 20% loss at 60 oC or 0.5% per degree above the lab 25 oC rating.

So, doing the sums backwards based on losing 0.5% per degree above 25 oC to get the loses the panel temperature should in theory have been 62.5 oC.

I also checked back on an okayish day like today which yields 17 kWh but the wind and lower roof temperatures managed to high full expected peaks of 3.995 kWp

C’est la vie, bummer !

I tip my hat to this man he deserves a medal, MBE, Knighthood.

The bar for ‘pro-DIY’ has been well and truly raised.

It is a well told story, actually more like incredible journey (those Disney pets had it easy) about the quest for a little more warmth and comfort in a home lounge/living room.

I remain inspired and in awe.

I am now getting gas usage data through to Google Power Meter.

I did mention a while back that a connection was established to the gas meter and being logged, but the data never up until now never made it through to Google Power Meter.  Here is the old article link

So those clever people at Brultech have now added a little more functionality to get the gas/counter displayed on the very useful Google Power Meter, here is a snap.

It is great to manage both energy utilities, though both work best once some history is collected.  Not sure if anyone else has done the Google Power meter for gas yet ?

Okay, it works and is useable though not perfect.  My display says kWh but it is actually m3 and Google only provides one costing rate so the financial figures are for generation.  I do wonder how much effort the Google people put in on this topic as it sounds spookily quiet on the help/forum.

Recap, how is it done ?
In summary, the Brultech ECM 1240 device channel 7 can be configured as a counter which is interfaced to the 0.01m3 pulses output from the domestic gas meter.  The Brultech EngineG software will then work out a rate measurement and post it off to Google every 15 minutes. Easy !

So what is NET metering ?

It is the ability to measure power/energy

  • Generated (for solar/wind)
  • Used ie how much the home consumes (That used to be easy!)
  • Exported back to the grid (basically = Generated – Used)

NET metering is really of value where there is some generation on site such as a wind or solar PV.  When these new investments are connected to the grid NET metering helps you keep on top of your usage and figure out how your big investment is doing along with tracking your new energy buying and selling profile.  Even better to be web based rather than hiding on those dials in the meter closet.

How can this be done ?

Measure Home meter power and the Generated power.  The measurements should be capable of totalising directional (polarised) energy flows and take account of power factors to give useable information.

Why ?

Well usually the inverters used by solar/wind give generated numbers and the utility supply meter usually only gives bought energy. The inverter interfacing can get complicated and is different for all the various types.

What Information is useful to know?

Basic stuff usually financial accounting reports or graphs like

  • How much £/$ has renewable generation made today/week/month etc
  • How much energy is consumed. Are we still reducing our carbon footprint ?
  • How much solar energy are we consuming/exporting.
    Again a green self-sufficiency angle and a costing exercise

It also helps if you can casually flick to your browser and look at this information in a simple way just like this Google Power Meter screenshot.

NET Metering Dashboard

NET Metering

How did I do it ?

Well it sounds like a product recommendation and it is.  The Brultech ECM1240 companion software has a NET metering configuration option.  Flick it on and bingo all the fancy directional energy flows are measured and posted off to google or a local dashboard.  Pretty neat.