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Heat pumps more effective than air conditioning during heatwaves

Air-source heat pumps are the best way of keeping US homes cool during extreme heat, while boasting lower costs and carbon emissions, reveals a study by not-for-profit RMI.

Heat pumps are more effective at maintaining a comfortable and consistent indoor temperature, and cost $228 less a year to operate than a dual fuel cooling and heating system (an air conditioning (AC) unit plus a gas boiler), states a report from not-for-profit RMI.

Carbon dioxide emissions were also 25% lower for homes opting for a heat pump over a high-capacity AC and gas boiler.

Locals and visitors cool off in the International Fountain in Seattle, Washington, July 2009. (Photo by Stephen Brashear/Getty Images)

The report modelled the performance of three cooling options for a Seattle home during a three-day heatwave in June 2021: an air-source heat pump, a typical 2-tonne AC unit and a higher capacity 4-tonne AC unit. Record-breaking heat has scorched parts of the US this summer. As demand for cooling grows, “it’s important to ensure that cooling equipment has minimal climate impact”, RMI says.

In Seattle, where 46% of single-family homes do not have air conditioning, heat pumps are “an attractive solution”, the report states.

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RMI calls on lawmakers and utilities to introduce incentives to make heat pumps more affordable, notably by reducing their upfront costs.

The report cites new US legislation as an effective example. The Zero-Emission Homes Act provides households with up to $10,000 in rebates – or $14,000 for low-and-moderate income households – to transition to all-electric homes.