4 steps to solar panels – a quick test to see if PVs could work on your roof

Over the last few weeks, I have talked to quite a few people about whether panels for electricity from solar ( photovoltaic panels (PV) ) are plausible for their roof. A lot of this is due to the government consulting on cutting support for PVs from January 1st (by up to 87%), meaning the financial payback on installing panels would typically increase from ~10 to 27 years. I’ve blogged before about when we when through the steps of getting our install together (to PV or not to PV), but I thought I would throw together a more general simple step-by-step…

If you live in a flat, the roof is one you do not solely own, or the install is on the larger side, some further steps are needed ( e.g. structural survey, certificate of easement…) however the general steps below are effectively the same.

      1. Work out a few details about your roof area and angle.

You will need to know roof area, roof angle, what angle it faces, how much shading it has, and whether the building has an energy performance above the minimal criteria (an EPC of D or above).

You can calculate the approximate area from eye or just use satellite photos. I tend to use Google maps through an app on a website like comparemysolar. Using this app you just place pins on the outline of the roof to get an approximate area. Google maps also gives you an compass orientation. As for angle, I would say it should be possible to get a estimate just from looking at the roof and comparing against a few examples. Then check for shading (e.g. chimney pots, neighbours roofs, trees…) and estimate what % of day you think the roof is shaded (another approach would just to check the roof at several times of day, but bearing mind this will change a lot by season). To check an the energy performance of the house according to its EPC certificate, and you don’t know it off hand, you can quickly check it on this website. If you do decide to get quotes, then all these estimates will be refined then anyway.

(e.g.  20 square meters, 30 degrees, south facing, no shading, EPC=D,  and in York)

      2. Estimate the rating of the PV install

There are lots of different panels of differing shapes, sizes, capacity and performance around. Choosing panels for the install may be easiest once you have quotes. I would recommend two sets of calculations, one for a lower capacity (e.g. ~100 W/sq m & cheaper) set of panels and one for higher capacity set of panels (~200 W/ sq m) . To get the peak output ( rating ) of the install just multiply the panel capacity by the area.

(e.g.  20 square metres * 200 W/square metres =  4000 W)

      3. Use some apps to estimate the output and payback of the PV install

We can now just plug the numbers from steps 1 & 2 to one of many online apps that use past solar data to predict how the panels would perform.  There are lots of apps to check whether PV is worthwhile and they give give a variety of different information from just the basic payback, to yearly/monthly break downs of energy production, and ones with lots of technical gory detail. I would personally recommend getting a broad overview from the Energy Saving Trust (EST solar calculator) and the Centre for Alternative Technology (CAT solar calculator, Caution: the monetary values were out of date when I last checked so just use for solar). If you are interested in more detail then the Joint Research Centre (JRC solar calculator) provides a lot more technical background.

The payback is made up of payments for generated clean renewable every (feed-in-tariffs or FITs), electricity savings (from use of electricity on site), and export tariffs (price paid per unit exported to the gird for someone else to use). The is more detail on this here and this will be broken down by the apps also. I understand that Installs for a typical residential install are generally between £4-6.5k at present.

(e.g. estimated to generate ~3300 kWh/year and have a payback of 9 years)

     4. Get a few quotes

There is a great list of recommended installers (need to be MCS certified) and a list of good questions to ask on the YouGen site. I also used the quote service from EcoExperts who quickly got us 3 quotes for comparison. The industry has taken a big shock from the recent government proposals to cut the fit in tariff and a lot of people may being trying to get installs before the expected changes to the tariff so it could be quite busy at the moment.

Once you have your quotes you can choose obviously between suppliers/installers, but also the capacity/spec of your install…. and whether you want to go ahead with it. The installs typically take a day for a 4kW domestic install and then the install will need to be registered via the installer through the government’s micro generation scheme (MCS), which installers tend to help with or just do for you.

Our installation was done whilst we were away on holiday; it was done quickly and without disruption.

(e.g.  Ecoexpert say from £3950 for a 4kW install. – Ours cost a little over £6k, but was rather technical and high spec for two years ago)


York Green Open Homes – Living in a “Eco” home

We’re part of York Green open homes this weekend! If you are about York, come see what “eco” measures people have done! These include from a “Passivhaus” under-construcion (more about passivhaus), 1960s council house, a 1930s semi, detached, bungalow, and many more. Green Open Homes is a national project and they have a even have a nice video intro of the project.

Frankly, flattered doesn’t quite cut it to explain how we feel about being asked to do Open Eco Homes. Our project is a lot smaller budget than a lot of projects you hear about. For the event, we’ll be showing how we reached our goal to take a thoroughly normal terrace home in York from a “D” to “A” grade (EPC) eco home for less that 10% of the value. We’ll show how we achieved that and also made our house a net exporter of electricity with low bills. There’s another aim we always had but didn’t mention often; we wanted to make sure it was still a “normal” home. One that we can live in comfortably, and be eco without having to drastically change anything about our lifestyle.


As the hosts (@StNicksFields) say: “Find out how to turn your house into a comfortable and efficient home from people who have done it!”

Us: We’re Not Hippies, Honest

Both of us have long been interested in the environment and technology that reduces our impact. That’s based on our concern about climate change. But being a scientist and an engineer, we’ve often noticed that we’re much more interested in the cold evidence than the sentimental stuff. You’re more likely to find us obsessing over doing our recycling correctly than getting upset about pandas.


This means we sometimes choose different paths to an eco lifestyle. A good example is being vegetarian – we’re not. A lot of our friends in the eco world are; some for ethical reasons, some for environmental impact. We like eating meat now and then so we’d find giving it up unenjoyable; instead we eat meat infrequently, and eat less of the most environmentally detrimental meats. Using the information we have, we can reduce our impact without having to change our underlying habits and lifestyle.


So this means we need an eco home where:
  1. we’re happy every change made had a rational, evidence-based argument to support it.
  2. little day-to-day input or behaviour change is needed from us.

Most of our blog topics have been info-heavy and focused on the numbers. This one catches us in a thoughtful mood as our Eco Open Homes weekend approaches and we start talking about what we’ll tell our visitors about what it feels like to live in a home like this.

Our “Eco” Home


The goal of this project was to convert the cheapest house we could get in York to a “A” grade (EPC) eco home for less that 10% of the value. We essentially achieved this. Due to cosmetic choices and additional non eco measures (like our FSC oak floor + relaying backyard with our reclaimed victorian tiles) it may end up being closer to 15%.


The project has involved some big changes such as installing solar power panels, insulating the floor and dealing with damp problems, and some smaller changes of insulating and draft proofing the house and installing a chimney pillow.


What’s it like to use electricity in an eco home?

Well, in 2014 we produced 3.4 MWh and in 2013 we used 2.6 MWh. So overall, we’re producing 130% of what we need. On the face of it, we’re golden. If we assume out consumption is constant and you look into it a bit further, it’s more likely that a portion of that 2.6 MWh came from the grid when it wasn’t sunny. So we sold spare units at sunny times, and bought National Grid units at others.

So we’re happy with the total amount of power we use. We do the sensible little things; we switch off stuff at the socket when we’re not using it. We hang clothes on a line instead of having a tumble dryer. But we keep an appliance others might identify as wasteful; a dishwasher. We just like it too much. Our routine is to wash up by hand, but when we have guests or have a big elaborate meal and then feel lazy, we love having that dishwasher. Over the year it looks like it’s OK really, so although we discussed ditching it we decided it wasn’t necessary.

Full array - extension and main roof
Full array – extension and main roof
The main change we made when the PVs were installed was not what we did but when we did it. It’s better for the environment if energy used in our house comes straight from the PVs, directly displacing a CO2-heavy unit of grid electricity. If we use power at night, we’re taking an eco hit twice; once because we’re getting grid electricity at a higher emissions content, and twice because we’ve sent our sunshine power to others via the grid at a noteworthy transmission loss; ~8 % doesn’t make it to the other end. That’s rubbish.
So, the washing machine and the dishwasher go on in the daytime. High energy stuff like the kettle and the shower are going to consume more than the panels punch out whenever you do them, but daytime is better, and when a wash isn’t on is better still.


There’s more we could do; we have an average kettle and an average shower and they use a lot of power. The shower is 8.5 kW. And we are both too addicted to long hot showers to ever get a shower timer. But we’re honest with ourselves that we enjoy these luxuries and we want to keep them.

What’s important to us is we never, ever have to say “you can’t turn that on”. We just get on with life as normal. You quickly forget why laundry-time is about 11am when the sun will be high and it’s just habit. We use our laptops a lot and have a constant tea-making operation going on. When we break 20 kWh in a day it makes us smile, but if it’s a rubbish

We like that any set of people could move into this house, and without changing a single bit of behaviour, they’d have a massively decreased electricity footprint.
With the recent developments in home storage batteries, Tesla PowerWall being the most widely-promoted, it could soon be even easier. 10 kWh storage provides 10 x long hot showers, maybe 60 x boiling the kettle. 2.6 MWh a year averages to 7.1 kWh a day. So this battery would instantly take our house off-grid for a long stretch of the year, since it could provide a day to two day’s power even if PV output is very low. Based on our 2014 generation data, we think we’d have around 200 consecutive days entirely grid-free; we’ll be able to calculate this better once the new Open Energy Monitor is installed. We’d only need to take from the grid in the depths of winter.


Is an eco home cold?
No, ours is pretty cosy. Because it’s insulated so well, the sunshine and the people tend to warm it up ok. We keep our gas boiler off completely between mid-March and mid-October. It doesn’t cause a problem. We have two little low-power electric heaters, 400 W each, which we specially bought to suit the PVs. If it’s a cold but sunny day, first port of call is to switch these heaters on to top things up. We’ll pick a room or two we’ll mostly be in for the day and just heat that area. When it’s a small house anyway this isn’t particularly difficult to accommodate.
If it’s both cold and overcast, we make use of the boiler. Because we both work full-time, it’s on a fairly restricted timer, and then controlled with a thermostat. We have a wireless one you can take with you. We carry it about so the temperature is set right for where we are.


Since our old boiler packed up and we got a new one, we’ve had new thermostatic flow taps on the radiators. They haven’t been very useful though, since if you change it and then move rooms you have to alter the taps set up again. We don’t really see the point, and we don’t really use them, they’re just all set the same.
New Boiler!
New Boiler!
It’s worth saying, our preference is for a moderate temperature in the house. We dislike having a home heated really hot, and we have both cultivated exquisite jumper collections we love to wear.


Sometimes our guests want the place hotter than we’d set it up. We will happily turn the boiler on outside of normal months for their comfort, and since the new boiler’s been in, it’s easiest to just hand them the wireless thermostat and say “set whatever you like”. It doesn’t make a big difference to the overall picture, it’s our day-to-day habits that influence it more.
What are the bills like?
Basically energy bills don’t exist for us anymore. We use about £25/month of grid electricity, and about £10/month gas which is heavily in the winter and obvisouly pro rata’d.


FITs and export tariff payments are made quarterly. Obviously they vary depending on generation. But it’s always significantly more than the energy bills.
So overall our house doesn’t cost us money to run, it looks after us.


Dealing with the rubbish


In the house, we recycle as much as possible. Our council pick up recycling for paper, card, plastic containers & caps, glass, and tins. There’s no food waste collection, but we compost our raw food waste/teabags for the community garden down the road. We collect up more unusual recyclables over time and take them to the main centre now and then; tetra pack containers, small electrical items, batteries, bits of metal, bits of wood. Old furniture goes to the community furniture warehouse or up on Freecycle. Old clothes go to the charity shop or the cloth bank if they’re really knackered. We’re in the habit of making use of packaging again in the house where we can.


By recycling everything possible, you become aware of it when you’re buying things and try to avoid them or only buy the minimum you need. So examples of stuff that’s a pain to dispose of responsibly  are paint/highly volatile chemical items, things that are not possible to disassemble like metal items moulded into plastic, food with tons of packaging particularly if it’s got foams, and cheap electronic items that won’t last long. Sometimes you have to buy them but it’s good to avoid just accumulating unnecessary stuff.


What goes in the general waste bin is mainly cooked food waste, plastic films, plastic-coated foils (like crisp packets) and expanded foam packaging. Actually food packaging and food miles/seasonality would be the next big thing to act on to continue getting our carbon footprint down.


Was it worth it?


We started this as we were fed up with what is described as affordable housing being completely not so (about us page). The money costs were largely as expected, the time costs were pretty high. It meant months of living in a not-finished home, of organising every detail of the bought-in work, and painting or sanding or sawing every night as soon as we got in from work. Occasionally we got really frustrated by it. But we’ve met our energy and cost goals, whilst making the house a cosier, cheaper and more sustainable place to live. We also got the chance to make a comfortable home that’s just right for us, and we’ve found it’s far easier here than in any rental places we’ve lived to follow an eco lifestyle even when you’re really busy. We think this place is set up so that anyone who lived here would be more eco even if they didn’t really think about those issues. We’ve always believed that living in an eco house should improve your quality of life too, and we feel like this house does that for us.


Yes, it was worth it!




“Roof-less” Micro-investing in Renewables – For when you can’t have panels, a wind turbine or hydro etc yourself…

This article is a little intro into buying into renewable projects from ~£5 upwards. Its something that I’ve been involved in for a while now and feel it has enormous potential, with billions per year being raised through crowdfunding. I often meet people who are interested in crowdfunding, but rarely people who know about the application to renewables.

Why micro/smaller renewables?

Renewables now provide 17% of UK electricity consumption (2013 data), with the majority of this from coming from the big six. This control within the market doesn’t exactly work for the consumer (nicely overviewed by this FT article) and it has led to a large amount of press coverage. This is continually brought up in government time and calls have been made to make the “big six” the big 60.000 instead ( e.g. from the Energy Minster Greg baker) . What if we as individuals in the population had a degree of ownership of this new energy generation? (e.g. fig. 1. >50% of share installed capacity in Germany in 2012) Could we direct more money into our communities? Would we feel more involved in tackling climate change? Could we increase the construction of renewables?

Performance of renewables and our policy driven goals mean that as well as the environmental motivations, from a business or investment standpoint renewables are great idea (A Government Minster even recently said “Solar panels [are] better than a pension“). This is further demonstrated by the press coverage and strength of the reverse argument: divestment. Here i’m going to run through the general money case and how to get involved and won’t cover the social and environmental side.

German energy transition is a democratic movement (Read more at 2.I – Energy by the people)
fig. 1 – German energy transition is a democratic movement (Read more at 2.I – Energy by the people) – Figure and Caption reproduced from energytransition.de

What if you don’t have space for PVs etc?

Due to renting, living in flats, urban locations or unsuitable roofs not all of us can have renewables on our own roofs or in our back gardens. However being part of the process of decarbonising our energy is something more people feel motivated to do. There are lots of worthwhile changes we can make to energy use in our houses, and this blog is charting our exploration into those, but importantly the choices and influence over energy delivered to our houses is also becoming within  grasp.

We can choose suppliers for our homes that aspire to reduced carbon content/100% renewables ( e.g. Cooperative Energy/Good Energy) or actively work to build renewable infrastructure (e.g. Ecotricity). Regardless of your position on energy generation the contribution of energy we use in our homes is ~30% of national electricity consumption (fig. 2) and energy generation is clearly going to be close to home for a lot of us in the future. Our little renovation in Yorkshire for instance is close to proposed/operating wind turbines (e.g. Private: Knabs Ridge; community: Blackshaw HeadGrimethorpe and Cudworth, Norton) and fracking exploration (Kirby Misperton); so getting actively involved becomes a much more present and proximate issue.

Ofgem: Electricity Generation: facts and figures - http://tinyurl.com/qzqp44v
Fig. 2 Ofgem: Electricity Generation: facts and figures – http://tinyurl.com/qzqp44v

Investment… don’t you need lots of money for that? 

Micro investment in renewables is where developers of energy projects raise the capital by lots of smaller “shares” to interested members of the public, rather than seeking larger amounts from fewer investors or banks. Billions of pounds have now been raised through crowdfunding by sites like Kickstarter, and it is a now an established investment model globally for renewables (fig. 3). Shares typically start from £5 upwards, and both community and private projects have gotten off the ground.  These projects generally have projected returns/ROIs of 5-7% or above, which is much higher than usual high-street cash rates (e.g. ISAs/Bonds etc). Typical recent examples are 6.65% IRR ( PV – SunShare) or 8.4% – 9.3% IRR (Wind – REG High down). The way they operate tends to be through raising initial capital through share or loans to setup the renewables and then the income is generated through selling the electricity and government payments for generating the electricity (FITs) pay the ongoing costs, community contributions and returns to investors. The play-off for the higher rates is due the decreased access to the money for the duration of the investment, longer terms (normally ~3-20 years), the return often is un-guaranteed, the capital is at risk and there is a lack of transferability (shares tend to be exchanged via mediated offers, dependant on buyers). Each project is different, and the terms will alter so weighing up of pros and cons has to be done on a project by project basis.

Global renewable crowdfunding
fig. 3 . Global renewable crowdfunding credit: @SolarPlaza via @TrillionFund 

Interesting, how established is it and is it for me?

Being part of renewables is now a choice open to all, which is starting to revolutionise the energy market and proving a game changer for schools, communities and companies. Although direct ownership arguably leads to the greatest returns if plausible (as I discussed a little when we installed our PVs), utility scale renewables are cheaper per kWh, and offer greater capacity and value to the consumer. Below are some related links including the main UK platforms and serval examples of projects being funded or just getting up running, and long term established projects.

Here are further some refs/links:

Disclaimer: I am not a financial advisor and do not work in finance. This article links to research/information I’ve found and expresses my own opinions and experiences.I hope it is useful to you but in no way am I offering financial advice or recommending a particular course of action. If you’re considering any investment you should seek information from a wide range of sources and speak to an independent financial advisor before making any decision. I’ve tried to be as accurate as I can, and when prices have been quoted those were available openly on the date of publication. If you see any errors/broken links/have any comments please just drop me an email or comment.