HEAT PUMPS | ZERO BILLS HOMES To be accredited as suitable for the scheme, a housebuilder must confirm a homes expected heating and hot water consumption, along with its expected solar-generated power appliance and cooking use. From that information, we will define an agreed specification with the housebuilder, which it then builds so we can accredit it as a Zero Bills home, he explains. Octopus acknowledges that geographical location will have an impact on eligibility. Homes in Scotland are likely to need a larger solar array and better thermal insulation to be eligible. If, having run its analysis, a plot is found not to meet the schemes criteria, the energy provider will recommend design changes to unlock eligibility. Approved suppliers The homes heat pump and battery must be able to integrate with Octopus Energys technology, so the energy provider can optimise and control its operation, says Banks. We dont tell housebuilders which model or type of kit to install, but it does have to be from our list of integrated suppliers, so we can optimise the equipments operation remotely, he adds. This includes most of the main air source heat pump brands, along with GivEnergy batteries. Typically, a battery will need to be sized to provide between 10kWh and 14kWh of power, while the PVs will be expected to deliver between 8kWp and 12kWp which, Banks admits, is quite a lot. Generally, this will require housebuilders to fit PVs to both sides of a homes roof to generate sufficient power. Zero Bills is not, in theory, confined to new-build homes. Octopus Energy says it is happy to assess any housing stock for compatibility. In practice, however, this means the thermal characteristics of existing homes must be at least as good as current new-build regulations. Anyone purchasing a Zero Bills home will have Octopus Energy as their default supplier. To benefit from the guarantee of Octopus Energys research facility in Slough Heating from an electric source must be specified zero energy bills for five years, the customer will have to agree to the energy providers terms and conditions. That means allowing Octopus to control the battery and heat pump settings in their home while they live and heat their home normally, says Banks. If customers are not happy, they are free to leave before the end of the five-year term. Banks insists that handing over control of a homes battery and heating to the energy provider is not as onerous as it might sound. The home owner sets the programmer on their thermostat as normal, he says. In the background, we are looking for full optimisation control on the battery to deliver the heat temperatures at the times customers want but we may choose to optimise when the heat pump is heating the domestic hot water, for example, and we may run the heating cycle slightly earlier if it is much more cost-effective to do so. By signing up for the Zero Bills scheme, householders are forfeiting the opportunity to earn revenue from their PV-generated electricity. Effectively, it is zero pence per kWh export, zero pence per kWh import, with a zero standing-charge tariff so you will not get paid for the energy 50 December 2023 www.cibsejournal.com CIBSE Dec 23 pp49-50, 52 Octopus heat pumps.indd 50 24/11/2023 14:50