Cooling demand across 241 major U.S. cities has risen 37% on average since the early 1970s, pushing household energy bills higher and concentrating financial pressure on low-income residents in the hottest states, where annual cooling costs already reached $712 in Arizona as of 2020. The trend, measured through cooling degree days tracked by NOAA, affects 97% of cities analyzed and is accelerating peak electricity loads that grid planners must meet with generation and storage additions. Heat pumps – which provide both heating and cooling at higher efficiency than resistance heating or older air conditioners – remain underdeployed in the regions where cooling needs are growing fastest.
Cooling Degree Days Are Rising Across Nearly Every Major U.S. City
Cooling degree days (CDDs) measure how much and how long outdoor temperatures exceed a baseline of 65°F, providing a standardized proxy for the energy required to cool buildings. Climate Central’s analysis of NOAA data shows that 234 of 241 major U.S. cities – 97% – have seen CDDs increase since 1970. The average increase across those cities is 37%, but the distribution is heavily skewed toward the Southwest, Southeast, and Southern Plains. Austin, Texas, cited as a poster child, exemplifies the trajectory: its summer temperatures now routinely sustain multi-week stretches above 100°F, a pattern that was rare five decades ago.
The metric translates directly to electricity consumption. The U.S. Energy Information Administration’s 2020 Residential Energy Consumption Survey – the most recent granular dataset available – shows household cooling expenditures ranging from $378 in Hawaii to $712 in Arizona among the ten states with the highest average cooling costs. Texas, Louisiana, Mississippi, Alabama, Florida, Georgia, South Carolina, and Nevada fill out the list. Those figures predate the inflationary period of 2021-2023 and the record-breaking summers of 2023 and 2024, meaning current out-of-pocket costs are almost certainly higher. EIA has not published a comparable state-level cooling cost update since 2020, a data gap that complicates budgeting for utilities, policymakers, and consumer advocates alike.
The burden falls unevenly. Low-income households spend a larger share of income on energy – often 10% or more – and are more likely to live in poorly insulated housing with older, less efficient cooling equipment. Older adults and young children face elevated health risks during heat waves, especially when nighttime temperatures stay high, preventing physiological recovery. The geographic overlap of high CDD growth, high poverty rates, and aging housing stock creates a compounding vulnerability that neither market forces nor current assistance programs fully address.
Grid Peak Demand, Heat Pump Adoption, and the Fossil Feedback Loop
The 37% rise in cooling demand is not just a bill-payer problem – it reshapes the generation stack. Summer peak loads in ERCOT, CAISO, PJM, and the Southeast now routinely exceed winter peaks, flipping the traditional planning paradigm. In ERCOT, summer peak demand has grown roughly 1.5% per year over the past decade, driven largely by residential and commercial cooling. Each additional degree-day of cooling load at peak hours requires dispatchable capacity or storage that sits idle for much of the year, raising system costs. If the CDD trend continues at its current rate – approximately 1.5-2% per decade in the fastest-warming cities – peak demand could climb another 10-15% by 2040 without efficiency gains or load flexibility.
Heat pumps offer the most direct technical countermeasure. Modern cold-climate air-source heat pumps deliver coefficients of performance (COP) of 3.0-4.0 in cooling mode, meaning they move three to four units of heat per unit of electricity consumed – far better than the effective COP of 1.0 for resistance heating and significantly better than aging central AC units rated at SEER 10-12. Replacing a SEER 10 unit with a SEER 18 heat pump cuts cooling electricity use by roughly 45%. At scale, that flattens the peak curve and reduces the capacity market payments that ultimately flow to ratepayers. Yet adoption lags in the hottest states. Texas, Florida, and Arizona rank in the bottom half of states for heat pump penetration as a share of residential heating equipment, partly because gas furnaces dominate existing housing stock and because upfront costs remain a barrier without targeted incentives.
There is a feedback loop worth naming: the fossil generation that still supplies 60% of U.S. electricity emits the greenhouse gases driving the temperature increases that raise cooling demand, which in turn calls for more generation. Breaking that loop requires both decarbonizing the supply side and reducing the demand side through efficiency and electrification. The Inflation Reduction Act’s 25C tax credit (up to $2,000 for heat pumps) and High-Efficiency Electric Home Rebate Act (HEEHRA) point-of-sale rebates (up to $8,000 for low- and moderate-income households) are the first federal levers sized to the problem, but implementation varies by state energy office, and contractor workforce constraints slow deployment.
Who This Affects
- Utility resource planners: Summer peak load forecasts must incorporate CDD trends that are non-stationary – historical normals understate future peaks by 10-20% in high-growth corridors. Integrated resource plans that rely on 30-year weather normals risk under-procuring capacity and storage.
- Storage and solar-plus-storage developers: The widening gap between midday solar output and late-afternoon cooling peaks (5-8 p.m.) increases the value of 4-8 hour storage in ERCOT, CAISO, and Southeast markets. Projects that can shift solar to the net-load ramp capture higher energy and capacity revenues.
- State energy offices and low-income program administrators: HEEHRA rebate rollout speed determines whether the most vulnerable households access heat pumps before the next record summer. States that pre-qualify contractors and streamline income verification will deploy funds faster and reduce LIHEAP cooling assistance outlays over time.
- Grid operators (ISOs/RTOs): Demand response programs targeting residential AC and water heating can shave 5-10% off peak in pilot programs; scaling these requires advanced metering infrastructure and compensation structures that reward sustained load reduction, not just event-based curtailment.
What to Watch Next
- EIA’s next Residential Energy Consumption Survey release: The 2024 RECS data, expected in late 2025, will provide the first post-pandemic, post-inflation snapshot of state-level cooling expenditures and equipment saturation – critical for calibrating assistance programs and utility demand-side management budgets.
- Heat pump shipment data from AHRI: Monthly Air-Conditioning, Heating, and Refrigeration Institute reports show whether IRA incentives are moving the needle in the Southeast and Southwest. A sustained inflection above the pre-2022 trend line (roughly 4% annual growth) would signal market transformation.
- ERCOT and CAISO summer 2025 peak load performance: Real-time data on how new battery capacity (15+ GW added in ERCOT since 2021) performs during multi-day heat domes will validate or challenge current resource adequacy models.
- NOAA’s updated climate normals (1991-2020 baseline, next update 2031): The shift from 1981-2010 to 1991-2020 normals already raised CDD baselines by 5-15% in many cities. The next update will embed another decade of warming into the planning standards used for building codes, utility rate cases, and infrastructure design.
Bottom Line
The 37% rise in cooling demand since 1970 is a measured, ongoing shift that is already baked into summer peak loads and household budgets – and the data infrastructure to track it in real time remains fragmented. Closing the gap requires treating cooling efficiency and heat pump deployment as grid reliability investments, not just consumer choices.
Read the full report at Energy Central
Note: facts and figures attributed above to reflect that outlet's original reporting. Broader context, cross-sector connections, and forward-looking scenarios reflect independent analysis by our editorial team.
About this article: Drafted by Energy Ai with AI-assisted research and writing based on public reporting, then reviewed under our editorial process before publication.
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