Super-low-carbon-homes case study: is it worth it?

When you modernise your home to cut its carbon footprint, you start with a sense of purpose. It reflects your belief system. However, after having done this we wanted to know: is it worth it in monetary terms? This article is a case study of just one home; “Superhome 59″ in High Wycombe, Buckinghamshire, UK that was retrofitted in a project that ran from 2008 to 2010. The home was built in the 1980s, has five (small) bedrooms and has about 120msquared living space.

The Green Deal will kick off at the end of January 2013 on the principle that you can select some energy saving measures for a home, install them, pay for them up front on credit and then pay it pack through savings on your energy bills. Of course not every home will have taken the “menu” of options chosen at Superhome 59. Some have an excellent payback. This case study does not attempt to breakdown the menus items. We poured everything into the same pot. We used insulation, draught-proofing, replacement doors, solar thermal panels, photovoltaics, a wood pellet boiler, energy saving appliances and lights. We attempted to completely squash our carbon footprint using brute force and something slightly-less-than-ignorance. How did we do?

Since the project kicked off on the day we moved into the house we had no baseline. So we asked our friends at the Superhomes charity to supply us with starting figures used in their own assessment. (Our thanks to Gordon Glass, John Doggart and Richard Macphail for this.) They supplied figures for our home using the NHERS rating system that was tested by BRE. (It should have a 95% accuracy. NHER covers more energy use than does the current SAP assessment.) According to this measurement Superhome 59 should use 38,322kWh (“units”) of energy per year broken down into 34,231 for Gas and 4,101kWh for Electric. I ran these numbers through our current Gas and Electric bills from NPower and calculated that this should be costing us £1,827 per year. The average UK household bill is £1,334. We’ll keep you in suspense for a few paragraphs before telling you how much we pay. There are a few facts of life to be explained first.

Today our gas usage is zero because we heat are home by wood (we’ll come back to that in a second). Electrical usage is 2,940kWh per year which is a 28% decrease. However we generate about 2,800kWh per year so are, effectively 95% self sufficient - unfortunately the sun goes away at night leading us to import energy. The billed import is 1,860kWh per year. Thus the bottomline electricity cost is £280 a year. But what about all that wood fuel?

We use about 4,515kg of wood pellets per year which equates 20,600kWh of space and water heating. That is a 40% saving on heating, but wood isn’t free. It costs about £0.25p/kg (pellets) which is about £1,100 a year. Add in the cost of electricity imports, logs for the wood burning stove in the lounge, maintenance & cleaning then the total cost to heat and power Superhome 59 is NOW £1,780 a year. Of course this is pants. A saving of £80 a year? But still this is not the whole picture is it?

That number is distorted because we used a renewable heat solution. It isn’t cheap. There is no current Government support mechanism for domestic renewable heat but this is slated to arrive in 2013. When that rolls in we will update this article. Until then there is one other significant support mechanism we haven’t mentioned yet: the Feed In Tariff. We get paid for the solar electricity we produce and we get paid well; about £1,600 per year in total (including payments for exporting electricity to the grid). This is tax free and increases every year with inflation.

So the total NET payment every year to heat and light our home is only £180. So we are saving £1,650 every year. Aha (I hear you ask) but what did it all cost? The total project cost was a startling £49,000 of which £4000 was not related to energy (for example: saving water, growing our own food, providing loft storage, and so on). Even at £45k that is a significant outlay by anyone’s standards. Most people will never earn that amount of money in any year, most will never buy a car for that amount, most could only dream of what that sort of money could yield in terms of luxury holidays. But, of course, you can borrow that money against your mortgage, if so lucky, to invest in your home. So the real question is: what’s the payback? Or, to put it another way: why not just invest that money somewhere else?

Now the maths could get complicated depending upon the discount rate you apply and assumptions about fossil fuel prices. But if we strip away the complexity and just use today’s prices then we get a payback of around 27 years - or about the length of a mortgage. To put it another way the return on investment is about 3.7% pa. (We didn’t compound the interest because you will need that to pay your bloated gas & electric bills.) So what is the opportunity cost? You could have put the money in the bank. If you reckon the economy will grow at an average of 3% pa for the next 30 years then it MIGHT still be worth it. Of course there are other investment packages out there depending upon the level of risk you wish to take. In our case investing in our home was a zero risk strategy hence we should only use the lowest estimate.

Of course this slightly misses the point. Even if you had stuck the money in the bank mostly every penny of interest you earn would have gone on your gas and electric bill. So you are just standing still. Your capital may be more liquid than ours but our home is still our home. We get somewhere to live that is warm and comfortable. You still have to live in your cold and draughty house. Which brings us to the next point: carbon.

It is fun to figure out whether such an investment is worth it in terms of Carbon Dioxide saved. Europe has a Carbon Trading Market known as the EU ETS. Currently one tonne of CO2 trades at just £6.58. So my £45k would have bought 6,838 tonnes of CO2. If I take the payback period of 27 years then in that period Superhome 59 saved just 211 tonnes of CO2. Putting it another way: it was 32 times more expensive to save carbon via a home retrofit than simply retiring carbon credits on the free market. My 211 tonnes earn me just £1,388 at today’s ETS price. Derisory.

Of course that tells you far more about the failings of carbon markets than it does about the foolishness of householders investing in their own homes. Carbon should be many more times expensive. The failings of the market have to do with how artificial it is. It was created by bureaucrats. What more can we say? It is not a measure of economic rationality. An Englishman’s home is his Castle. The Government’s Green Deal is testimony to that.

The bottomline is this: we generate 95% of our own electricity, cut our electric bill by 28% and our heating bill by 40%. However the sledgehammer we used proved to be so expensive that it only becomes worth it because of the Feed In Tariff. Even then the total project payback is quite low and only slightly better than leaving your money in the bank. Then you have to factor in the cost of replacing the renewable energy devices. The photovoltaics may well last 40 or 50 years but the electronic box of tricks that connects it to the grid will need replacing within 10 to 20 years. Then there is that biomass boiler. It might last no more that 15 to 20 years. If you replace a gas boiler it might set you back £1,800 whilst the wood pellet boiler might cost £9,000. There is nothing clear cut about this decision. What you get is satisfaction. It isn’t about being smug. It is about security. Whilst everyone else’s bills went up 7% in 2012 ours went up by 1.3%. We have disconnected ourselves for the death spiral of fossil fuels.

So maybe “is it worth it?” is the wrong question. Maybe we should be asking “if we knew this would it have changed anything?” To that the answer is truly “no”. Definitely not. What if we frittered that money away on holidays and fast cars? After 27 years we would have no cars, no holidays and we would STILL be paying through the nose to heat and light our home. So it was a wise investment because in year 28 it is still costing us less. Maybe not that much less – the Feed In Tariff ends after 25 years – but this home will probably stand for a hundred years or more with its carbon footprint 90% lower than similar homes.

What we need is perspective. Our children’s children may well look back upon this home at that time and wonder what sort of people were we? I look at old pictures of my great grand parents and ask the same question. One built railways across India, another manned an observation balloon in World War One, they were astonishing people. We all hope to leave such a legacy. We might never lead the exciting lives that they did but our legacy stands all the same. It is always worth it – because a Superhome is always extraordinary.

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