Anyone who has been researching energy efficiency for their new home will have become used to the term ‘fabric first,’ as this is still very much the best method for achieving high energy efficiency levels.
When it comes to zero bills, the less energy you need, the easier it is to draw it all from renewables and remove your reliance on the pay-for grid. But, is this achievable by retrofitting an existing home?
If you are building a new home from scratch, the goal of achieving a very high performance fabric is a little less complex, as you're not dealing with an existing structure that is complicated, unknown and very often expensive to treat.
Article continues belowBut, when renovating, it's often trickier. That said, once you have treated the fabric of the home as best as you can, that is when you can get an energy requirement calculation and determine which technologies are best suited to delivering comfort to the home, and how close to ‘zero’ you can actually get.
What does zero energy bills really mean?
Zero bills can be defined in a number of ways. Having absolutely no direct running costs may be the initial understanding of the term, and it is true to say that if we put enough solar panels and batteries on a home then we could potentially have a home that had zero bills.
However, the capital cost would be very high, so the question is, should this calculation also include replacement cost of equipment, as this would then require the home to generate an income that was sufficient to cover capital replacement?
The more common use of the term zero bills has usually involved some form of offset. This can be referred to as ‘Net Zero’. The home generates enough energy to cover its use in a fixed period, which is usually a year. The generation will be greater in summer, and the use is greater in winter, but on average they cancel each other out. This can be calculated on an energy used basis, or on a financial cost basis.
It's also common to hear of performance targets such as Passivhaus in relation to Net Zero or zero bills. These are much more achievable on a new build. The retrofit equivalent of Passivhaus is EnerPHit which has certain details that are different, due to the fact that some things simply cannot feasibly be achieved on an existing building.
EnerPHit is however still a very high standard, and as such many homeowners do not set the bar that high, due to budget, average home prices in the street, or simply due to the disruption and expected project duration. It is nonetheless important to know where the bar is being set.
Achieving zero energy bills in an existing home
Energy use is simple to calculate. If you use 10000kWh per year then you need to generate 10000kWh per year. Some purists say that if you use this calculation method you should generate around 20% more than you use to account for grid losses.
However, when we look at the financial cost, things get a bit more open to context. Zero bills in this context is often referred to as ‘cost neutral’ or ‘cost positive’ depending on if you generated more income than your energy bills cost.
Historically, the Feed in Tariff for energy generated on solar photovoltaic panels was many times higher than the actual cost per unit of imported electricity. Therefore the early adopters were earning around £2,200 a year tax free, when their annual energy bills were only around £1,200. This was cost positive.
But, because energy prices rose a lot quicker than inflation, and generation income revenue rates tumbled, it soon became the case that the generation income did not cover the cost of the energy bills. It then became more important for homeowners to find ways of using less energy in the home by insulating, draught-proofing and turning appliances and heating off, or down, when not required.
It also became very important to use any energy generated at the time it was generated. Careful consideration of energy management in the home became increasingly important.
Appliances such as washing machines, tumble dryers and dishwashers that could be set up to automatically operate during the day, are now standard for better managed homes. Battery storage systems have become more popular, especially as installation costs fall. The uptake of electric vehicles has also meant that excess energy generation can be stored in the vehicle battery.
All of these technologies, including the increased installation of heat pumps, are based on electricity. The collective term being used for all the electric based products being installed on our homes is ‘electro-tech’ and by deploying smart electro-tech into our homes, the management of energy use becomes easier.
How energy companies are encouraging zero bills
Octopus Energy has embraced the zero energy drive and launched – Octopus Energy Zero Bills Homes. With this scheme, the energy use of your home is calculated and the scheme will guarantee you have no bills for 10 years providing you install solar PV, solar battery storage, an air source heat pump and use an electric vehicle and let them manage it.
This is currently available on certain new build properties with various terms and conditions and fair use policies but Octopus Energy is planning to roll it out to include retrofitting in existing homes too.
I can only see this growing and other energy companies following suit. It’s the way homes are being developed now. We no longer fit industrial infrastructure to houses. We instead manage the homes as complete energy systems, which includes changing how, and when, we use energy.
In my view, zero bills is not a pipe-dream, it's real and it’s happening now. It is however easier to achieve if you have lower energy use to start with. The lower your energy use, the smaller your electro-tech, and therefore the lower your capital costs and the better your return on investment.
Achieving zero bills is not difficult, making it pay for itself though, requires careful planning and managed work.
To start your journey towards a zero energy bills life, you'll need to firstly understand how to work out your energy needs and choose the right renewables. Then, make sure you understand the key fabric first factors such as the best types of home insulation to ensure your home isn't leaking heat before you start.
