Domistic Energy Consumption

There are two ways to reduce emissions and increase energy  security.  The first is to use less energy and the second is to generate it from renewable sources.  The two approaches are not mutually exclusive and both are desirable but they compete for resources.  Around 2006, I became interested in renewable energy, up to that point, I had not thought too much about consumption.  Typical grid-tied PV solar instalations produce between 1,500 and 2,500 kwh/year.  A good starting point was to try reduce our consumption to the level at which a form of self-sufficiency could be attained.

Alongside my interest in renewable energy, is a belief that investments which are good for the environment, should also make some economic sense.  In other words, I'm prepared to buy an item which reduces my emissions, but I want to be rewarded in the form of lower energy bills.  For energy consumption, and therefore emissions to fall, there should be a "virtuous circle" by which I use less energy and am better off as a result.  This should be possible to achieve, energy is expensive.

This is were the fridge comes in.  Back in 2006, the first fridge we ever bought as a married couple was sitting in the corner of the kitchen consuming between 1 and 2 kwh/day, for an outlay of around £130, this was replaced by modern one with a consumption of less than 0.5kwh/day.  Assuming we use 1kwh/day less at an average cost of £0.10/kwh day, we got payback in something like 4 years.  E.g. the planet is happier and I'm better off.

Location, Location and Location

The comments on this page are based on my own experience, no two households are the same, but I suspect an audit of energy consumption in most homes and offices would suggest cost-effective improvements.

Our Audit

To the amusement and embarrasment of the dog and my family, I purchased a plug-in energy meter, took notes, and produced the  the graph below:

This effort produced some quick-wins.  The easy one was lighting.  In 2006, energy efficient lighting was just becoming available at an affordable price, in 2011 its more or less the accepted standard.  Replacing old incandescent bulbs with CFL's took 5kwh/day from the total for a spend of less than £100.  Over a two year period, a computer network that was a hangover from from life as a software developer was replaced with a couple of laptops.  Lurking in a cupboard was gas boiler with reproduction Victorian plumbing, on a good day this would struggle for a couple of hours to produce a luke warm bath, thus anyone needing to leave the house clean, would turn on the immersion heater.  The gravity feed hot water heating was replaced with a pumped system which produced hot water in a matter or minutes thus allowing the immersion heater to be retired.

Have the Meter Readings changed?

Electricity consumption has dropped from around 20 kwh/day to around 6 kwh/day.  This is shown in the plot of random meter readings:

Part of the downward trend is children leaving home for institutions with decent plumbing, but also taking care with the selection and use of appliances.

Doctrine of Unforeseen Consequences

At one point, the house served as an office extension, sometimes with two or three people working in it.  The computer network provided much of the heating.  These days, its just me, a dog and a laptop and in winter the room where I work is ****** cold.  The loss of heat from the computers is occasionally replaced by an open fire (often with wood picked up whilst walking the dog).  Simply turning on central heating would offset the gains.

Law of Diminishing Returns, but.....

I see no obvious way of making further reductions without creeping around the house with a candle.  However, LED/Solid State Lighting is making progress and whilst not an option now, may become one in the not too distant future.  This could get our lighting consumption down to less than 0.5 kwh/day.  Approximately 50% of the electricity that we consume is in devices which operate at low DC voltages,  the conversion from 240V AC is mostly done in inefficient power supplies (often called wall warts).  If we adopt LED lighting the proportion of the electricity we consume at low voltage DC will approach 80%.  This suggests that within the house, a low voltage DC distribution system with efficient DC/DC conversion where needed might offer significant savings from one efficient unit rather than twenty or more inefficient ones.  There are safety issues with such a scheme and devices with high instaneous demand, e.g. the washing machine, do not fit well in this scenario.  But 2 - 3 kwh/day might be possible.