A heat pump moves heat instead of making it: in winter it pulls heat from the outdoor air and brings it inside, and in summer it runs in reverse as an air conditioner. In Menlo Park, West Menlo Park, Atherton and Portola Valley, where winter lows sit in the 40s and summer afternoons reach the 80s, that suits the climate well. Most projects replace an aging gas furnace and AC in an older ranch home, swap a worn heat pump, or bring heating and cooling to rooms the ducts never reached.
Sizing for heating and for cooling
One machine does two jobs, so it has to be sized for both. A room-by-room load calculation works out how much heat the house loses on a cold night and gains on a hot afternoon; the larger number sets the capacity. In a shaded Menlo Park ranch house with single-pane windows, heating may lead. A Portola Valley hillside home with big west-facing glass may need more capacity for cooling.
The common mistake is matching the new unit to the old furnace’s label. An oversized heat pump short-cycles, pulls little moisture out of summer air and swings between warm and cool. Variable-speed (inverter) equipment runs slowly on mild days and ramps up on the few cold mornings. With lows in the 40s, many homes need little or no electric backup heat; whether to include it is a load and panel decision, not a default.
The electrical panel
The outdoor unit needs a dedicated 240-volt circuit and the indoor unit needs power; backup electric heat adds a large circuit of its own. Many older ranch homes have a small panel already carrying a dryer, a range or an EV charger. Before quoting, we check the equipment’s circuit requirements and run a panel load calculation:
- There is room: the breakers go in and the install goes ahead.
- It is tight: a model with a lower circuit requirement, little or no backup heat, or a load-management device can avoid an upgrade.
- An upgrade is needed: it can involve the electric utility, so it is scheduled first.
If an EV charger, induction range or heat pump water heater is on your list, say so now and plan the panel once.
Ducted, ductless or a mix
Ducted. If supply and return ducts are in fair shape, an air handler goes where the furnace was and the registers stay. Heat pumps deliver air at a lower temperature than a gas furnace, so leaks and missing insulation in older attic ducts are felt more. We test the ducts and quote duct repair where it matters.
Ductless. Wall, ceiling or floor heads, each with its own control, fed by one or more outdoor units. They suit houses without ducts, additions, garage conversions and the far bedroom that never got enough air. See ductless mini-split installation.
A mix. Large Atherton homes often run two or more systems, so one zone can convert at a time, or a guest wing can go ductless while the main house stays ducted.
Where the outdoor unit goes, and who hears it
On many Menlo Park lots the old AC condenser sits in a narrow side yard near the neighbour’s bedroom window. A heat pump also runs on winter nights, so placement matters more than it did for an AC that ran on summer afternoons.
- Compare published sound ratings. Inverter units spend most of their time at low speed, which is quieter.
- Keep the unit away from bedroom windows, yours and the neighbour’s, and out of corners where walls bounce sound.
- Use a solid pad or ground stand with vibration isolators; brackets on a bedroom wall carry vibration inside.
- Keep the manufacturer’s airflow clearances, and send defrost water somewhere other than a path or the fence line.
- Setback and noise limits are set locally, so the spot is checked against the town’s rules before the permit.
On Portola Valley slopes, add a level pad, a spot out of falling leaves and pollen, and the manufacturer’s limits on line length and height difference between the units.
Replacing a gas furnace
- All-electric. The furnace comes out, an air handler goes in and the gas line to that spot is capped. If the furnace shared a flue with a gas water heater, the water heater’s venting is rechecked.
- Dual fuel. A heat pump paired with a gas furnace that takes over below a set outdoor temperature. Fewer electrical changes, but two systems to maintain.
An air handler’s size differs from the furnace’s, so closets get measured, and attic installs need a drain pan and condensate line. The thermostat must support heat pumps; see thermostat installation. If you only want a new furnace, compare furnace installation.
Install day and startup
A typical install takes six to ten hours: old equipment out, outdoor unit set, refrigerant lines run or reused, wiring connected, indoor unit placed, then the system pressure-tested, evacuated and started. Current equipment uses newer refrigerants, so reusing an old line set depends on its size, condition and the manufacturer’s instructions. Startup proves the work: charge set for the line length, airflow measured, both modes run, defrost checked.
What moves the price
Most installs fall between $4,000 and $15,000. The low end is a single ductless zone or a heat pump replaced in the same spot; the top is a whole-house ducted system replacing a furnace and AC, with a new line set, a long run to a side yard or slope, a tight attic and duct changes. Ask whether panel work and duct repairs are in the price or separate line items. Get matched model numbers, efficiency and sound ratings, the electrical scope, permit and exclusions in writing.
Rebates and credits
The federal tax credit for heat pumps ended for equipment installed after December 31, 2025. Other kinds of programs remain: utility rebates, regional and state programs, and manufacturer promotions. Before counting on one, check that funds are still open, whether approval is needed before installation, which models qualify and whether the installer must be enrolled. See our rebates page.