Why is my electricity bill so high? – Heat pump FAQ answered

Paul Spence, Technical Manager for heatly, looks at one of the main causes of high electricity bills and the key steps that installers should be encouraging their customers to take before the heat pump even goes in.

As we all know, heat pumps run on electricity, so when the temperature drops, electricity usage goes up, something some consumers feel more keenly, depending on their house and the install.

Firstly, I think it’s worth noting that heat pump owners tend to pay a lot more attention to their bills compared with some gas boiler customers. The technology is not yet widespread in the UK, some consumers are nervous about the switch and as the majority of us have a smart meter in sight, it’s easy to watch the Kw’s and pounds rise.

Secondly, it’s important that end users take an annual view, there will of course be the odd expensive day, but the cost of running a heat pump, or any heating for that matter, should be looked at over the course of a year. A fixed tariff can sometimes work better for people who want to stabilise their outgoings – costs may be higher during the winter, but the cheaper summer months should even things out.

The best thing you can do to help your customers reduce their bills is to encourage as much heat loss prevention as possible. Quantifying the savings of installing insulation and other draught proofing measures may have been hard in the past, but new technology is painting a much clearer picture which makes an investment in energy efficiency hard to ignore.

Any heat pump installer worth his salt wants as high a COP as possible, getting your customers on board with this aim from the outset is the ideal scenario.

Insulation save £s To demonstrate the benefits of insulation on heat pump performance, I used the heatly app to compare heat loss surveys for the same property, each with varying levels of insulation. This functionality is currently in the trial stages (you can sign-up for trials, here).

The results showed that the addition of basic loft and floor insulation reduced heat loss by 45% and saved a whopping £1,000 a year in fuel costs.

The house

We made our heat loss calculations based on a 4-bedroom house with a total floor area of just over 200m2. We assumed an outside temperature of -2.2°C and a ground temperature of 6°C.

Report 1 – Zero floor or loft insulation

We start with our house in a considerable state of disrepair with no floor or roof insulation. Heat loss was calculated at 16,420 W and total annual consumption at 36,100 kWh.

Assuming electricity costs 30p/kWh, a heat pump running at COP3.5 would cost £3,094.28 per year:

36,100 (kWh) / 3.5 (COP) x 0.30 (electricity unit price) = £3,094.28 (annual running costs) excluding standing charges.

Most of the heat loss was from the roof (6.5 kW) and windows and doors (3.5 kW), with walls and floors also leaking heat.

Report 2 – Floor insulation but zero loft insulation

We then added *150 mm of PIR floor insulation to our hypothetical house. This lowered the heat loss to 15,029 W and the total annual consumption to 32,506 kWh, around a 10% reduction.

Using the figures above, a heat pump running at SCOP 3.5 would cost around £2,786.23.

*I realise that that 150mm of PIR may not always be possible to install.

Report 3 – Floor insulation and loft insulation

Finally, we added 300mm of mineral wool loft insulation in addition to the floor insulation resulting in a heat loss of 9258 W and a total energy consumption of 20,045 kWh, a reduction of 45% compared to no insulation at all.

A heat pump running at SCOP3.5 would cost £1,781.10, or if you could hit SCOP4 you’d be looking at annual energy costs of just over £1,500, an impressive reduction of more than 50%: 20,045 (kWh) / 4 (COP) x 0.3 (electricity unit price) = £1,503.38

Fabric first pays off!

Imagine we are renovating our house, uninsulated with an old gas boiler operating at 80% efficiency. Assuming a gas unit price of 7p/kWh it would cost £3,158.75 a year to heat: 36,100 (kWh) / 0.8 (efficiency) x 0.07 (gas unit price) = £3,158.75.

Replace the gas boiler with a heat pump and you’d still be looking at annual costs of over £3,000.

But add the floor and roof insulation at the same time and costs are reduced by close to half as a basic starting point. Further energy efficiency measures, such as replacement windows and doors, or internal wall insulation will result in further heat loss and cost reductions.

Compare this scenario with a property that puts heating systems before insulation – maybe retrofitting happens 2 or 3 years after the heat pump is installed, with new window, roof insulation etc – consequently, the heat pump and pipework could be grossly oversized leading to a myriad of problems for the user: increased short cycling, excess energy consumption, poor lifespan of equipment due to increased starts per hour; basically high costs and poor performance.

Whilst the initial price of fitting insulation may be quite hight, it’s a one-off fee. The benefits of reduced running costs are year on year. There are grants available for inefficient and/or low-income households, including the Great British Insulation Scheme and ECO4 which covers energy efficiency improvements alongside a heat pump upgrade.

A good heating installer should always try and ensure the best-possible outcome, and explaining the savings that can be made by investing in a fabric first approach will lead to happier customers with warmer homes and cheaper to run heat pumps.

This approach is best for all homes, regardless of the heating type.

Learn to install insulation with GTEC! GTEC is currently offering fully funded online draught proofing and insulation training, ideal for installers looking to offer a more total solution. For more information, visit: https://gtec.co.uk/courses/online-insulation-courses

Get hands-on with heatly at InstallerSHOW 2024. InstallerSHOW is heading to the NEC Birmingham from 25-27 June 2024. Register for your free entry pass here: https://installer-2024-splash.reg.buzz/inst-site-news