How To Not COP It - Part 2: Home Energy

The next in my short series of positive stories on how you can take action and do your bit to be more eco-friendly is about home energy. Cutting the costs, consuming less and creating your own.

It’s no secret that energy costs are very high right now. The price of natural gas is high and this pushes up the price of electricity too, as gas is the main form of peak generation in the UK.1 The costs are not just monetary but also environmental due to the emissions from burning gas and other fuels.

The last few decades have shown that you can’t convince people with simple things such as evidence, facts, data, maths and science alone. You can’t just be right but need to tell compelling stories. By stories, I don’t mean the lies told by Tufton Street lobbyists such as The Global Warming Policy Foundation (now rebranded Net Zero Watch, how meta).

I mean stories that make the truth real in people’s minds by bringing alive what the future can be like and what is possible (while still being honest about the downsides). So this is one of our stories about what we have done and what the future could look like for you.

We moved home over a year ago and have done lots of work to make the house cheaper to run and have a lower environmental impact. Here is our experience of this (incomplete) journey.

Minimise

The first way to cut costs is to consume less energy. Very soon after moving in we replaced all the lightbulbs with LED ones.2 These use much less energy than incandescent bulbs and also less than older energy-saving fluorescent tubes.

The washing machine needed replacing (as it was damaging clothes) so we swapped it for a more efficient one. We make sure any appliances like this have a timer so that they can be run overnight if required. We generally wash overnight and dry clothes outside in the day if the weather permits.

Insulate, Retain

Insulation can be a bit dull but it is a cheap and effective way of cutting costs and retaining heat. The loft was poorly insulated so I bought about 10 rolls of loft insulation and laid it up there. I also insulated some pipes and water tanks.

We got cavity wall insulation installed. This involves drilling holes into the outside of the house and blowing lots of balls made from recycled paper into the air gap to improve heat retention. A government grant contributed towards the cost of this.

We replaced the front door as it was very draughty (and insecure). We also had some window hinges replaced for the same reason.

“Smart”?

One of the first things we did was get a “smart” meter installed. This was to replace a first-generation “smart” meter that had become dumb rather than an old dumb meter.

The benefits of “smart” meters have been miscommunicated. The main claimed benefit is that the meter doesn’t need to be read manually but we still have people coming to the door to read it. Billing is also more erratic than when we were supplying manual readings (I believe due to the unreliable data comms rather than the energy company). Not very smart.

Aside; the term “smart” is so overused when providing a worse experience that whenever I see it now I mentally replace it with “stupid”. For example, when the control room cat gets loose and constantly changes the speed limits on a “stupid” motorway for no apparent reason.

The In-Home Display (IHD) from the meter can be useful to see instantaneous energy usage and tracking down energy vampires but this has been available for many years from a simple current clamp. Ours mostly reads around 0W now anyway, more on that later.

The actual benefits of smart meters (to the consumer) are that you can be billed for what you use in each half-hour period rather than just on aggregate and it can measure exports separately in a similar way. We used to be on the Octopus Energy Agile tariff but switched to the “Go” tariff to make things simpler and cheaper (after Brexit came into force and wholesale energy prices rocketed).

Between 00:30 and 04:30 electricity is just 5.00p/kWh inc. VAT and the vast majority of our usage is within this window. Our average cost per unit (from our bill) is under 6p.3 If you’d like an Octopus Energy switching bonus of £50 credit then you can use our referral link.

It’s worth keeping an eye on whether the rate boundaries are occurring when you think they are. You may assume that a “smart” meter with a mobile data connection would have an accurate clock, but this is not the case.

If you are getting a “smart” meter installed then it may be worth asking to have a separate double-pole isolator and circuit breaker to match your fuse rating put in at the same time. This can make working on your consumer unit (distribution board) and installing a car charger or solar PV system easier in the future.

Most of our radiators have Thermostatic Radiator Valves (TRVs) installed and we also have a handful of motorised ones that learn what time of day each room is used (using light levels). I replaced the mechanical house thermostat with a wireless digital one that can be controlled remotely. We also have a heat pump with WiFi connectivity but I’ll write about that in the next post.

Here Comes The Sun

The above are reasonably affordable (or sometimes even free) and simple home improvements that many people could make easily but we also made a larger investment in a solar PV and battery storage system this year. It’s early days but so far it is working out great and has significantly reduced what we pay for our electricity (even outside of the summer months).

You can make a lot of economic arguments and do calculations on breaking even etc. but I won’t do that here (although I have done the maths and it works out well for us). These sums usually make assumptions that energy prices will remain steady but as we have seen over the last year they can rise dramatically. Also you wouldn’t use similar arguments to justify many other home improvements. I have never heard someone say that they are getting a new kitchen because it will pay itself back within 10 years due to the savings they’ll make on food preparation.

We got a relatively small system of 10 panels installed due to limited available roof space (and allowing for a potential future loft conversion). The small size of the system means that you don’t need prior approval from the distribution system operator and the installers simply need to notify them.

We have two arrays, a smaller one facing roughly East and a larger one facing roughly West. We get some shading from trees and neighbouring buildings (particularly in the winter) so have optimisers on each panel. We also have wire mesh fitted around the edge to deter birds from nesting under the panels. Although this arrangement gives a lower peak output than a South facing one, it gives a longer generation period. More is generated later in the day when demand is higher.

Generation varies a lot depending on the weather. It has been as high as 18 kWh/day and as low as 1 kWh/day. It also varies throughout the day.

Storage

The more interesting part of the system is the storage component and we have two batteries installed totalling about 7 kWh (although not all of this capacity is useable). The inverter is a hybrid one and uses the batteries as a buffer. It has a current clamp around the grid feed and tries to keep this measurement as low as possible. If the panels are generating more than is needed then it will charge the batteries from them and if the panels can’t supply enough for the house then the batteries will be used to top it up (or supply it all at night).

This buffer significantly improves the utilisation of the solar generation. You can charge a battery slowly for a long time then use it quickly to supply a high power appliance for a short period when you need it.

I have the built-in timer on the inverter set to charge the batteries from the grid during our off-peak window (and I change the charge rate a few times a year based on generation). This prevents the battery from being drained when the car is charging and also helps minimise peak import in the morning. It is worth checking this is working as expected and building in some error margins because the clocks can be wrong (particularly on the meter).

If we’re only using one hungry appliance at a time (e.g. kettle or oven) then we won’t be importing any electricity. This keeps our average electricity unit price very close to the off-peak rate and we reduce strain on the grid by minimising import at peak times (when demand and high carbon intensity are high).

Negatives

Scaffolding is a pain (as it is for any building project) so if you have the space then it may be better to install panels in the open or on an outbuilding. However, the batteries need protecting from frost if they are installed where it can get very cold. The batteries are a large part of the cost of this system, along with installation (the panels were pretty cheap).

We get paid for exporting power but this is not very much and is less than the cost of importing (even off-peak), so the best thing to do is to use as much of it yourself as possible (but not waste it). When we have excess in the summer I charge the car (at a slow rate of 6A or 10A) or use the immersion heater to heat hot water. The house battery takes care of buffering any variability if it is a partly cloudy day where the sun goes in and out.

In the next post I’ll tell you about our heat pump and the many advantages it has over other forms of heating.


  1. Office of Gas and Electricity Markets - wholesale market indicators: “Electricity prices are heavily impacted by rising gas prices because of the importance of gas-fired power stations as the marginal unit to meet demand. This is the most significant driver of the increase in wholesale electricity prices.”
  2. In a couple of cases I replaced the whole light fitting as either the bulbs were hard to get hold of or were unreliable. This can work out better but can be a slightly larger investment and more effort (particularly if you are renting).
  3. For new customers the off-peak rate is still 5p but the peak rate is now higher than what we are fixed on. Although the peak rate has gone up the standing charge has gone down, so this might actually be cheaper for our usage profile as we use very little peak power. We don’t have a full year of data yet so the average will likely go up a bit. Our overnight EV charging and home solar + storage system plays a large part in keeping this average down and you also have to consider energy losses a bit.

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