Reducing your household running costs

A heat pump runs on electricity, which means the time of day you use that electricity has a real bearing on what your heating costs to run. Paired with solar panels and battery storage on a time-of-use tariff such as Octopus Cosy, which is designed with renewables in mind, your home can draw much of its heating energy from cheaper off-peak power rather than expensive peak-rate electricity.

In simple terms, a typical time-of-use tariff might charge around 28p/kWh at peak times and around 14p/kWh off-peak — roughly half the price. The opportunity is to shift as much of your heating and hot water demand as possible into those cheaper windows. Solar PV and a battery storage system are what make that possible.

Why timing Matters

A STIEBEL ELTRON heat pump turns one unit of electricity into roughly three to four units of heat. Where a modern gas boiler is around 95% efficient, a well-installed heat pump operates closer to 300–400% efficient. That efficiency alone makes it a more economical way to heat a home than gas or oil.

The second factor, and the one that is often overlooked, is the price you pay for each unit of electricity. On a flat-rate tariff, you pay the same amount whatever the time of day, so there is nothing to gain from when you use your energy. On a time-of-use tariff, the price varies through the day, and that variation is where the savings sit.

The aim is to schedule heating and hot water within the cheaper periods, gently warming the home and the hot water cylinder ahead of time, and to draw as little as possible during the expensive peak. A heat pump provides steady, consistent heat, and a well-sized cylinder holds hot water ready for when it is needed, so this can be done without any loss of comfort.

A tariff like Cosy only rewards a home that can move its demand into the cheaper hours. Each part of the system has a role to play in making that happen.

• A heat pump provides the heat efficiently, though its running cost depends entirely on the unit price you pay.
• Solar PV generates free electricity by day, directly powering the heat pump and charging the battery.
• Battery storage stores cheaper off-peak or solar power, then releases it during the expensive peak hours.
• Energy management ties it together, charging at the cheapest times and running the home from stored energy when rates are high.

Individually, each of these reduces your costs. Designed and installed together, as a single integrated system rather than separate purchases, the benefit compounds.