In a typical year, this house needs 13,692kWh for space heating and 2,186kWh for hot water. In a particularly cold (1 in 20) year, it might be 11% higher. Space heating and hot water requirements are evaluated annually as well for a typical day in each month of the year, also covering electricity requirements for air and ground source setups with standard, oversize radiators and underfloor heating. Analysis is derivied using hourly weather data for the property's exact location going back to 1940 covering air temperature, soil temperature, wind and air pressure. For the heat pump options, where the efficiency of the appliance is also weather dependent this means that the projections are internally consistent.

The maximum solar PV capacity identified from satellite imagery for this property is 8kW spread across 2 arrays on different roofs of the property, which if pursued to the maximum results in typical annual generation of 5,944kWh, however this is highly seasonal and will vary between a typical 2.3kWh/day in the darkest month and 31.8kWh/day in the sunniest month. Solar potential is evaluated using satellite imagery to identify the maximum capacity of solar panels that can be installed on the property. We join actual hourly historic weather data going back to 1940 (covering different forms of solar radiation that reach the ground) with LIDAR shading data that shows for every hour of the year which points on the roof would (even in a cloudless sky) be shaded by surrounding objects such as trees, neighbouring properties etc. We use this in turn to inform which panels (if any) on each array would benefit from installation of PV optimisers, which prevent the shading of one panel from affecting the output of the others. After evaluating each array separately, we rank the arrays from the highest yielding (usually south facing) to the lowest to give you at a high level the most intuitive options for different amounts of PV capacity. This sliding scale menu of options is used to estimate the total PV generation which as you might expect, varies significantly day to day and seasonally.

The maximum battery storage capacity is 30kWh. The battery storage analysis takes into account both the energy demand (including from winter heating) and the potential solar generation of the property. For more expensive (but electrically efficient) heating systems (e.g. ground source and underfloor heating) the optimum battery storage capacity may be lower; likewise with a boiler due to lower electricity demand. We assume the demand for electricity for other appliances (heating, lighting) is around 10KWh in line with the national average, with a shape that skews toward the early evening and morning periods.