One year on from the inverter upgrade

We installed our PV panels in 2011 and last year we upgraded the inverter system, installing SolarEdge equipment. We were promised better yields, but are we getting them? After one full year with the new inverter I have a reasonable answer. In this post I show how I have estimated the improvement, correlating yield with the old system with weather data from the MET office and using this to predict what we would have got recently if we had not upgraded. The prediction function I derived was 98% accurate, which I was very pleased with. Using this I have estimated the improvement to be 5.9%.

How much water is it OK to waste?

All water companies waste water through not fixing leaking pipes. This is OK up to a point. There is something called a 'sustainable economic level of leakage' which is the level where the cost of fixing leaks and the cost of not fixing them balances out, taking into account environmental costs. Obviously environmental costs are hard to put a finger on. So what is acceptable?

Climate change in Cambridge

We know global temperatures have been increasing - it is happening here in England too. Here are some charts based on MET office monthly average data since 1910 [1]. The clearest changes are in minimum temperature. I see no trends in rainfall, which surprised me.

These are for East Anglia (which includes Cambridge where I live). The blue lines are the 10 year running average. The first chart is for August. There is considerable variation even in the running average and the increase is not linear but is more marked since about 1995.

(max - min) for the running 10 year mean is 2.1C. In my lifetime the change is 1.3C.

More energy label confusion coming

Under the EU energy label scheme appliances were originally labelled A-G with A as the best. Then as standards improved new grades were introduced: A+, A++ and for some products we now have A+++; apparently this is confusing. So the EU is updating the scheme with a rescaling so everything goes back to A-G: they say this is simpler. However, during the changeover period we will see two kinds of labels which is going to be even more confusing. Fortunately for most products there is other information on the label that you can use to compare products by actual energy consumption. Unfortunately this is not so for heaters, which only show the energy class and even this means different things for different types of heater.

Reasons why your freezer may be using too much electricity

Back in 2014 I reported some shockingly high energy use in a minority of freezers and fridges [1]. This was from a study of electrical appliances in general and there were only about 130 cold appliances in the sample. Now there has been a much bigger study with 998 fridges and freezers, conducted by BRE [2]. It has confirmed the earlier findings and provided more information as to the causes of the problem. In some cases the appliance was faulty but half the time the main cause was simply running on fast freeze or maximum setting all the time.

This problem mainly affects freezers. 25% of chest freezers were over-consuming and 12% of upright freezers.

Reducing my carbon footprint without saving money

Usually I focus on home energy but recently I have been thinking about reducing my whole carbon footprint. It turns out I can use the same principles I have been using for home energy across other sectors too. Some of these strategies save money, but there are ways to spend it again and still save emissions.

I reckon the footprint for me and my beloved looks something like this. Yours will probably be somewhat different – for example ours is very low on travel because neither of us commutes to work, we don’t even have a car, and we usually take our holidays in the UK by train. However we are not unusual in that goods and services is a large chunk. So what can we do to reduce emissions over all sectors?

Carbon footprint for my household, estimated based on home energy use, travel distances and spending on other goods and services.

Do modern homes overheat more than older ones?

Modern homes have a reputation for overheating more than old ones partly because they tend to be more airtight and partly because they are often more lightweight constructions that heat up quickly. However, overheating is not an inevitable consequence. For example features such as green roofs and external window shades can make a huge difference – but apparently ‘people are resistant to changes to the aesthetic of the homes and other buildings they occupy’ and these features ‘may be resisted by house buyers’ – so builders won’t build them [1]. Is it all our own fault then?