We hope you enjoy this post from Zero Chippenham’s James Bradbury on how he’s saving money and carbon in his home by ‘load shifting’. The post is kindly taken with permission from James’s website 

Introduction

Domestic energy use costs money and causes carbon emissions. You may wish to reduce both. One way is to add renewable energy technology to reduce the environmental impact of your home, but this may not be affordable or practical for everyone. In this post I’ll describe a simple and cheap way to reduce both financial and environmental burdens.

Load shifting – what and why?

Of the energy people use in the home, some is used without much choice over when it is consumed. Examples include lighting, which is needed after dark and cooking, which typically happens around mealtimes. Other devices like fridge-freezers, internet routers generally run all the time, but consume only a small amount of energy. However, a lot of domestic energy consumption is not time-critical and can reasonably occur anytime within a 24 hour period. For example, washing machines, dishwashers, bread-makers, dehumidifiers, electrical heating systems including heat pumps and electric vehicle charging can all be used more flexibly at different times of day.

Why would you want to do this?

Saving carbon

Although the percentage is falling, electricity generation in the UK still involves fossil fuels. Most of this is now gas which results in greenhouse gas pollution in the form carbon dioxide when the gas is burnt and, even worse, methane, when it escapes.

However, the use of fossil fuels to generate electricity for the grid varies considerably by time of day. Currently there are insufficient renewables attached to the grid to cover peak usage. When this is the case, often gas plants will be turned on to make up the shortfall. This is expensive to do, so it increases the price of electricity. This is a good reason to get solar panels, but you can also load-shift some of your energy consumption outside of peak hours.

The availability of renewable electricity will also vary according to the weather and time of day. Solar power is only available during daylight hours and is greatest on clear days. Wind generation often complements solar, as the wind blows at night and throughout the year. Long-distance transmission lines can provide power as long as the wind is blowing somewhere around the country. However, there are times when there is neither enough wind nor solar and fossil fuels are used to fill the gap.

This variation in the use of fossil fuels for energy is called carbon intensity. There’s even a website to track and forecast it.

Saving money

Energy providers are increasingly providing variable rate tariffs. This is because the cost of energy that providers have to pay varies dramatically during different times of day. When demand is low, the wind is blowing and the sun is shining, electricity can be very cheap. At peak times, additional gas plants need to be started up which is expensive, even before they’ve started providing any electricity. Predicting and balancing the energy supply and demand on the grid is a complicated business. Much of the transmission capacity cost is only required to cope with peak demand.

It makes sense for electricity providers to pass part of this cost or saving on to customers. This makes the provider more competitive and can encourage customers to shift their energy loads outside of peak times.

Most electricity tariffs provide time-of-day rates. For example, the Cosy Octopus.

For a peek at the innovation Octopus are starting and what the future of electricity might look like, see this interview with Greg Jackson of Octopus.

Fortunately, cheap electricity generally aligns with low-carbon electricity, especially wind, so you can save money and carbon at the same time.

How to load shift electricity

So it’s clear there are advantages to using electricity at optimal times. but what are the easiest ways to do it?

Measure usage?

Before you start, it may be worth getting an energy measurement plug to gain an understanding of how much energy an appliance uses during typical use. That way you won’t make any effort for a small gain. On the other hand, you may be confident to judge roughly how energy intensive your appliances are without instrumentation. With the exception of a fridge freezer, large white good tend to use the most.

Heat pump schedule

Since replacing our gas boiler with an air-source heat pump, it has accounted for a significant proportion of our electricity usage. Thankfully, it’s simple to control the timing and temperature via the control panel in the garage. I’ll describe our overall strategy rather than the detailed steps.

First, it’s worth noting that while heat pumps are intended to run all the time, except in the most extreme weather, it is usually fine to turn them off for a few hours without losing much heat. As long as the building is well-insulated, the internal walls, furniture act as thermal mass, storing heat while the heating is not running. As long as the inside temperature has been high enough for several hours, it won’t drop quickly as soon as the heating is turned off. So we use can use in the inside of the house as a heat battery.

To do this, I’ve set the heat pump thermostat to a slightly higher temperature, two to three degrees higher than usual, during the off-peak, cheap electricity times. These periods are only three hours long so the house is unlikely to reach the higher temperature until close to the end of the period, if at all. But it does allow us to build up a little heat before the price and carbon intensity rises.

During the standard rate electricity, the heat pump continues running, but the thermostat is set lower. So if it is an especially cold day, heating will stay on continuously, but in milder conditions it will turn off as the price rises.

Only during the peak period of 4pm to 7pm does the heat pump turn off entirely. During this time the temperature will drop slowly, but so far we’ve never needed to manually turn it back on.

Finally, we’ve set the heat pump to heat our hot water during the cheaper periods as the insulated tank will store this for many hours without losing much heat.

Smart plugs

For smaller devices, you could invest in smart plugs and a system to control them all, attach one to every significant appliance and set it up to make the best use of tariff you’re on. Unless you’re on a very complicated tariff such as Agile Octopus which changes on an irregular schedule, I think smart plugs are overkill. I suspect that their additional complexity and reliance on wireless communication may cause them to fail, misbehave or have security issues. I certainly don’t think it’s worth using them on lights, if saving energy is your goal. It might make sense from a security point of view however. That said, I don’t have much experience with this technology, so others may find them useful.

Built-in appliance timers

Some appliances have a build-in delayed start or finish time. This is usually the easiest way to shift your energy use, once you’ve got used to the interface. In our house we do this with the bread machine and dishwasher. Only the bread machine requires a bit of compromise as it has a five hour programme which won’t fit into a three hour cheap period.

Electricity timer plugs

Two mechanical timer plugs with UK sockets. The one on the left has retained switches. The one on the right has a larger ring with removable pegs.

These gadgets have been available for years. The non-digital ones are very reliable and consume minuscule quantities of energy in their own right. I’ve used digital timers before, which have a backup battery so that they stay in sync in the event of a power cut, but I’ve found them unreliable and the batteries will fail without warning.

The two shown above are simple mechanical timers. The one on the left has a more user-friendly design. The blue ring contains switches which can be pushed in for “On” and pulled out for “Off”. On the side is an override switch which turns the plug on, no matter what the time switches are set to.

The one on the right works just as well, but override is achieved by twisting the red switch in the top right anti-clockwise by a single click. This is fiddly to do, especially if the timer is in an awkward position. It also differs in that the override can change manually to “on” or “off” and only remains until the next timing pegs passes it. That’s the other difference. The timer pegs on the timer on the right are not permanently attached, but can be pulled off the ring to slot in at another time. That means they can easily be lost on the floor, etc.

Mechanical timers are almost silent. Up close, in a very quiet room it is possible to hear a rapid ticking noise, but I’ve never found this annoying. Digital timers will be quieter, but all of them will produce an audible click from the relay when they change between “on” and “off” states.

Using mechanical timers to load-shift a digital appliance

The easiest way is of course to start the appliance manually at the correct time, but as one of our cheap periods is in the small hours of the night, I’d prefer to be asleep. Even the daytime periods I can easily forget once I’m working.

One of our more power-hungry appliances is our washing machine. A typical wash consumes between 0.3kWh and 1.2kWh. Not huge but it adds up over a year and makes no difference to us what time of day it happens, so we might as well load shift it.

A UK electrical plug plugged into a wall socket via a mechnical timer. Override switch is shown on the side.

It’s a Miele W5740 with a digital display to program it rather than a mechanical dial and hard on/off switch. I had thought that this meant I couldn’t simply use a timer plug to control when it starts. Recent experimentation has confirmed that the programme is retained when the power is cut. I can see this being a useful feature in the case of grid power outages. It’s likely that other washing machines will work the same way. If so, load shifting is as simple as:

• Set the timer plug to be “on” during the cheap period(s) you wish to use
• Plug the washing machine in via the timer plug and switch the override to “on”
• Load the machine and set the programme as desired
• Press “Start” button
• Wait a few seconds to ensure the wash is starting
• Switch the override back to “off”

Once the wash has finished, empty the washing as normal. If your door lock is electronic, you may need to use the timer’s override switch again.

Conclusion

We hoped you liked James’s insights into Load Shifting, Saving Money, and Saving Carbon. If you’d like to read more of James’s blogs and articles please visit his web page https://thinks.jamesbradbury.co.uk/