We live in a world where new is good, progress is essential and “only dead fish swim with the stream”. Our decisions are strongly influenced by all these, sometimes conflicting, societal norms.
It’s very reasonable to argue that the money I have is there to be spent on things that make me happy. This is particularly true if I’ve worked hard for this. So why should I not treat myself to a new appliance, fridge or dishwasher, especially if that has a higher efficiency rating?
That’s what we did when we moved into our new home, we got A rated white goods and those all important halogen spot lights. It was a celebration of having made it and a reward for our efforts.
Several years later, some of the appliances looked a bit old and tatty, time to get a more efficient upgrade. We’d learnt a thing or two about energy and associated emissions, thanks in particular to a couple of books:
- Energy and Carbon Emissions- Nicola Terry
- How bad are Bananas- Mike Berners-Lee
Instead of relying on our gut feeling, which is so readily influenced by what others say and what we’d ideally like to do, we decided to calculate. The well-known concept of payback was recommended by the first of these books. We could use it to make an informed decision on both financial and carbon payback time.
Payback time is essentially working out if this is longer or shorter than the expected life of an item we want to replace. This needs us to know how much it costs to run the old item compared to the new item, the cost of the new item and its expected lifespan.
We did this every time we felt we needed to replace something, the fridge, car, light bulb, etc. Basically, anything that uses energy, that’s practically everything. So here is the equation we used to see if it was time to replace our A rated fridge/freezer:
Money payback time in years = cost of new thing / (annual costs of old thing – annual cost of new thing)
Carbon payback time in years = emissions of making new thing / (annual emissions of old thing – annual emissions of new thing)
Getting the money numbers was easy enough, measure the energy used and multiply by what we pay for this energy. At the time 1kWh cost us 9p, so
Money payback period = £450 / (365 x 1.2kWh x £0.09 – 365 x 0.6kWh x £0.09) = 23 years
Carbon payback period = 200 kgCO2e / (365×1.2kWh x 0.52 kg – 365×0.6kWh x £0.52kg) = 1.8 years
Ok, financially it made no sense, but we’d make an appreciable dent into our Carbon Footprint after less than 2 years. Since then, electricity prices have increased and we worked out that by setting the fridge to 6oC and defrosting the freezer every 6 months or so, we consume 0.4 kWh per day instead of the 0.6 kWh stated by the manufacturer for that A+++ model and subsequently measure to be that.
Getting a ‘quality’ product pays off in several ways, that new fridge is still going strong after 14 years and we still feel good about owning it. Postscript: three years on we inherited a newer auto-defrost fridge/freezer. We measured this at the same temperature setting, unsurprisingly it used 0.2 kWh per day more energy. That’s 73 kWh more consumption per year. The benefit of not having to defrost manually every 3 months, a much newer device and the ability to pass our old fridge on to replace a very inefficient one, made the decision relatively easy.