Microgeneration and Solar Power

So… here’s our first ‘info-blog’ where we try to share some of our research and experiences with you guys in case you are considering something similar – or just because you want to regale your friends down the pub with newfound greeny knowledge.

There’s SOOOO much information out there about renewable energy in general and solar panels in particular that I obviously can’t give you more than an ‘amuse bouche’ without going on for hours. The aim, which I’ll try to keep in mind, is to consolidate the days of trawling through websites, talking to engineers and nosing through text books and give you the key points that led us to make the decisions that we have over our solar installation. I’m also going to assume that you have a desire to reduce your impact on the environment and reliance on fossil fuels… I don’t have the energy right now to be persuading the cynics.

I’ll pitch it at the novice and keep it quite general, so if you do want extra info, don’t hesitate to get in touch. And beware – I’m NO EXPERT so don’t take my word for it if you’re making any decisions… ask one!

Making the choice

That nagging itch over energy sustainability, reliance on fossil fuels, pollution and the hole the energy companies are burning in your wallet is beginning to become a little much… what are your options? Well, I’m going to break down a home’s energy requirements into 2 areas; electrical and heat. These, I believe, form the largest and most logical groups of energy consumption in the household

(In later posts we might consider light, kinetic/gravitational and chemical energy all of which play their own critical parts…).

This first instalment focuses on electricity and next time I’ll waffle on about heat.


Electricity is a wonderful source of energy – clean to use, easy and fast to move around… just a little tricky to store and our methods of creating it are woefully inefficient (usually ending up with a load of heat funnily enough). We all use, to a lesser or greater degree, a significant amount of electricity at home with our electrical appliances ranging from the ‘heavies’ like tumble dryers, vacuum cleaners and irons, often vocally showing off their 1000W+ power consumption, to the low-drain bits and bobs like the standby on your TV (maybe 0.5W) that plod away for long periods in the background. All this lot adds up to about 5,000 KW hours per year for the average UK household… or running a 1000W appliance for 5000 hours!…

The place to begin with all energy consumption is a simple question – can I reduce how much I use? With electricity, there are some very simple steps to reduce your consumption. Here are a few:

Saving Electricity

  • Know which things in your house use what in terms of electricity, especially things that are on for long periods of time like fridges, TVs, computers. Can they be used less or turned off more rather than left on standby? Do I really need to iron my frilly smalls? Do I need to leave all the lights on all the time? If you are using electricity for heating can you insulate more or turn the thermostat down?
  • Can I replace certain requirements with either more efficient or renewable sources? For example – can your property make better use of natural light (more windows, sun tubes, skylights etc), can you replace the tropical fish tank with a cold water one? Can I put the fridge against a north-facing wall rather than next to the oven? Anything that is fighting against the equilibrium is costing energy… whether it’s brighter, hotter, colder or moving faster than its surroundings (2nd law of thermodynamics for you physics-bods).

Generating Electricity

So now you have changed your gadgets, environment and behaviour to reduce your electricity demands as far as is reasonable you have to consider where your electricity is going to come from. Almost all of us are in the starting position of being ‘grid-tied’. In the UK this means we have alternating mains current at 240V coming straight into our house from the ‘national grid’. The grid is the network of electricity generators (power plants) and capacitors (big battery-type things) around the country linking every home to a power source. Here in the UK we generate something like 400 TWh (or 400, 000, 000, 000, 000 Wh!) from mainly Coal, Gas and Nuclear sources. But what are your options at home?

Realistically these can be narrowed down to a small group. I’ve listed them below with some pros, cons and pre-requisites.

Method Pre-Requisites For Against
Solar Between South-East and South-West facing unshaded space > 10sqm. Sufficient sunlight hours. 



Simple, readily available installation. Feed-in tariff. 



Lowish efficiency and very sporadic. Often high generation during periods of low usage. High potential energy in construction. Relatively expensive.
Wind Location with good laminar wind flow pattern and a high average speed.  


[Look up wind speed here]

Space for a potentially large installation.







Reliable in certain locations and with installations over a certain size.  


Readily available. Feed-in tariff.






Small installations can be unreliable and inefficient.  


Apparently can be noisy and create background vibration.







Hydro-Electric Rights to a good head of water with a high flow rate Very reliable and? quite efficient. Often tricky installation, needing land movement etc. Potential ecological impact. Rare that a property has the potential to use this method.









Source of biomass, subject to regulation Old, developed technologies. Can use waster material. Expensive, dangerous process. Needs continual attention. Often difficult to get hold of domestic sized equipment. Efficiency drops with drop in size.
Tidal / Wave Tidal source with access rights Very reliable May be difficult installation. Very rare that property has rights? or opportunity to install.
Anaerobic Digestion Eh? ? ?

Normally these few factors will allow you to narrow down your options to one or maybe 2 (hopefully not 0). For us we knew immediately that Solar was the only viable option – but the property was well suited to it.


Solar Photovoltaics – The system

First decision: Grid-tied or not? In my view there are many advantages to a ‘grid-tied’ system and not many of an ‘off-grid’ system. Here are some…

A grid tied system doesn’t need huge banks of batteries to buffer your energy use for times when you actually need it. You can contribute energy back to the grid when you are making more than you need and draw energy from it when you are not making enough. Your appliances will not notice any difference.

My advice – unless you’re worried that the apocalypse is coming or you aren’t currently on the grid, then stick to an ‘on-grid’ system. You can always convert later.

What kit?

The components of a PV installation are pretty simple:

There’s the panels themselves and an inverter (and a few bits and bobs like isolator switches and meters).

Inverters take the Direct current from solar panels and match them to the Alternating current of the grid. They don’t vary hugely so go for one that is robust, gives you the display that you need, isn’t too noisy and has good efficiency.

The main considerations, in my view, when choosing your PV panels are (roughly in order of importance) reliability, cost per KWh, efficiency, aesthetics. If you are limited in terms of space, then the efficiency may trump cost as it may be more important to get greater output for a limited area. The big emphasis in the press is about efficiency, but if you think about it you can quickly invalidate any small efficiency saving by adding one extra panel, especially if that panel will last 10 years longer.

So, look for a good guarantee on power output (our PhonoSolar panels, and I believe several other manufacturers, offer 80% output after 25 years) and look for a reasonable cost per KWh produced. As mentioned efficiency is not as important as it is made out to be and is pretty dire anyway but, as a benchmark, you may see anything from 12 – 20% efficiency, with a good modern PV coming in at around 18%. You will also quickly notice that some panels are ‘monocrystalline’ and some are ‘polycrystalline’, with the latter being cheaper. This relates to the number of silicon crystals within each photovoltaic ‘cell’, with a smooth, monocrystalline structure capturing more sunlight and hence being more efficient. However, on a price per W calculation the panels tend to even out, so actually this feature is not usually critical unless, again, space is a limiting factor.


If you want to get the feed-in tariff you will need? an MCS accredited installer. The job is not particularly difficult but is obviously a specialism so go through the normal sort of due diligence that you would for any tradesman. It shouldn’t take more than a couple of days to complete with minimum impact.

Financial Payback

There are currently 3 financial incentives to installing solar panels in the UK. The first, and biggest, is the Feed-In Tariff (FIT). This means that the government will pay you 43.3p per KWh of electricity generated (for installations under 4KW on an existing building), meaning for a medium-sized installation you may receive £1,000 per year (NB: This FIT is index-linked with [RP] inflation and guaranteed for 25 years). It’s important to note that this is for ALL of the electricity generated and not just that over and above what you use at home.

Next is your saving on electricity. Depending on how frugal you are and how much you can focus your electricity usage around peak production times, you will be able to save a varying proportion of your electricity bill by using your own electricity, rather than that from the grid. This should save at least £100 from your annual bill.

Finally your electricity company will pay you a measly contribution for any electricity that you have actually ‘fed back’ to the grid. Let’s say £50 per year.

So, annually, you might expect £1,150 for a medium-sized installation, which would cost you around £10,000-12,000. As you can see this gives you a, not amazing, but nonetheless not awful payback period of around 10 years. With life expectancy of the panels being at least 20 years this should mean that there is more than 10 years of ‘profit’.

Energy Payback

Hopefully money is not the only (or even main) reason for installing solar – the other being a reduction in your environmental impact. Some arguments used against solar panels is their intensive production process means that there is a high burden of energy ‘tied up’ in them that needs to be overcome before they break even. It is difficult to form a consensus from decent empirical studies, but the best meta-analysis that I’ve found is here: http://www.energybulletin.net/node/17219

and it comes out with a figure of 3.8 years. This, again based on our 20 year life-expectancy, doesn’t seem like a huge hurdle before we are ‘in the black’.

Future technologies:

There are many options available now for PV installations, some are newer than others and have not yet been used over a number of years. You can get, for example, hybrid systems that combine heating and electricity, thin-film panels, integrated ‘tiles’ that form part of your roof etc. etc. These should all be considered and taken on their merit for your circumstances but make sure you have confidence in their reliability – this is not a short-term venture.









Some Useful sites

For general site for discussions of renewable energy, click HERE

For Ofgem official site for Feed In Tariff, click HERE.

For a good sumary of Solar Electricity, click HERE.

Discussion of ‘netting off’ your electricity use: HERE

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