How Many Solar Panels to Run a Heat Pump? (Calculator + Examples)
A central heat pump uses 5 to 15 kWh per day depending on its size, the climate, and whether it is in heating or cooling mode. You need 4 to 10 standard 400W solar panels to cover it at 5 peak sun hours. Heat pumps are the most efficient electric heating and cooling technology available -- delivering 2-3 times more heating per watt than resistance heaters -- which makes them the ideal partner for solar.
Quick answer
A 400W solar panel produces about 1.66 kWh per day at 5 peak sun hours (400W x 5h x 0.83 derate). A typical 3-ton heat pump uses about 10.8 kWh per day (3,000W running, 8 hours, 45% duty cycle), so 7 panels cover it with headroom, though 8 panels is a safer target for winter heating when solar output drops.
| Peak Sun Hours | Small (1.5 ton) | Medium (2.5 ton) | Large (3-4 ton) |
|---|---|---|---|
| 3 PSH (very cloudy) | 7 panels | 10 panels | 14 panels |
| 4 PSH (cloudy) | 5 panels | 8 panels | 10 panels |
| 5 PSH (US average) | 4 panels | 6 panels | 8 panels |
| 6 PSH (sunny) | 3 panels | 5 panels | 7 panels |
| 7 PSH (desert SW) | 3 panels | 5 panels | 6 panels |
Formula: panels = daily kWh / (panel watts x PSH x 0.83 derate), rounded up.
Heat pump energy breakdown
Heat pumps do not generate heat -- they move it. In winter, they extract heat from outdoor air (even cold air contains thermal energy) and pump it indoors. In summer, they reverse the process and work as air conditioners. This thermodynamic trick gives them a COP (coefficient of performance) of 2.0-3.5, meaning they deliver 2-3.5 kWh of heating for every 1 kWh of electricity.
| Specification | Mini-Split (12k BTU) | Mid-Size (2.5 ton) | Large (3-4 ton) |
|---|---|---|---|
| Running wattage | 1,000W | 2,000W | 3,000-5,000W |
| Hours per day | 10 | 10 | 8-12 |
| Duty cycle (heating) | 50% | 45% | 45% |
| Daily energy (heating) | 5.0 kWh | 9.0 kWh | 10.8-15.0 kWh |
| Daily energy (cooling) | 3.5 kWh | 7.0 kWh | 8.0-12.0 kWh |
| COP at 47 degrees F | 3.0-3.5 | 2.8-3.2 | 2.5-3.0 |
| COP at 17 degrees F | 2.0-2.5 | 1.8-2.2 | 1.5-2.0 |
Variable-speed (inverter-driven) heat pumps adjust their compressor speed to match the load rather than cycling on and off. This results in more consistent temperatures and 15-25% lower energy consumption compared to single-speed models at part-load conditions.
Try the calculator
Adjust the panel wattage and your location's peak sun hours to see exact production numbers for your setup.
Benchmarks: U.S. avg 4.98 · Phoenix 6.54 (highest) · Seattle 3.95 · Anchorage 3.17 (lowest). Above ~5.5 = sunny · 4.5–5.5 = average · below 4.5 = cloudy.
Tap to see sensitivity analysisSensitivity analysis
| Scenario | Value |
|---|---|
| Low (-20%) | 1.3 kWh |
| Expected | 1.6 kWh |
| High (+20%) | 1.9 kWh |
Your daily production scales linearly with both panel wattage and peak sun hours. A 10% change in either input changes your result by 10%.
Running it off-grid
Heat pumps are one of the best heating options for off-grid solar homes because their high efficiency translates directly into fewer panels and smaller battery banks compared to any resistance heating method.
Battery bank sizing (for a 3-ton unit at 10.8 kWh/day):
- Daily consumption: 10.8 kWh
- Autonomy target: 1.5 days (heating is critical and winter storms reduce solar)
- Total energy needed: 16.2 kWh
- At 48V with lithium (LiFePO4) batteries at 80% depth: 16.2 kWh / 48V / 0.80 = 422 Ah
- This typically requires 4 units of 48V 100Ah server rack batteries
Inverter sizing: Single-speed heat pumps have significant startup surges -- 3 to 5 times running wattage. A 3,000W unit can spike to 9,000-15,000W momentarily. Variable-speed (inverter-driven) heat pumps have soft-start circuits that limit surge to 1.5 times running wattage, making them far easier on off-grid inverters. For off-grid use, choose a variable-speed unit whenever possible.
For a single-speed unit: pure sine wave inverter rated at 6,000W continuous with 12,000W+ surge. For a variable-speed unit: 5,000W continuous is usually sufficient.
Winter considerations: Solar output drops 30-50% in winter compared to summer due to shorter days, lower sun angle, and more cloud cover. If you live in a northern climate with 3 PSH in winter, you need roughly twice the panel count from summer calculations. In practice, many off-grid homes pair solar with a backup propane furnace or wood stove for the coldest, cloudiest weeks.
See our battery charging calculator for exact sizing.
Running it grid-tied
Grid-tied solar paired with a heat pump is one of the most effective home energy strategies. The two technologies complement each other across all four seasons.
Summer: Your panels peak at 6-7 PSH while the heat pump runs in cooling mode at lower energy demand. You generate large net metering credits.
Winter: Your panels produce less (3-4 PSH in northern states), while the heat pump works harder in heating mode. You draw down summer credits through net metering.
Spring and fall: The heat pump runs minimally, and your panels produce strong output. These are your biggest credit-building months.
Over a full year, a 3-ton heat pump using about 4,000-5,000 kWh (combined heating and cooling seasons) can be fully offset by 8-10 panels producing approximately 6,000 kWh annually. The surplus covers other household loads and provides a buffer for unusually harsh winters.
The 30% federal solar tax credit and various state heat pump rebates (often $2,000-$8,000 through the Inflation Reduction Act) make this combination increasingly cost-competitive with gas heating.
Energy-saving tips for heat pumps
These strategies maximize your heat pump's efficiency and minimize the number of solar panels needed:
- Choose a variable-speed (inverter-driven) unit. Variable-speed compressors adjust output to match the load, using 15-25% less energy than single-speed units that cycle on and off.
- Keep the outdoor unit clear. Snow, leaves, and debris on or around the outdoor unit restrict airflow and reduce efficiency. Maintain at least 2 feet of clearance on all sides.
- Change filters regularly. For ducted systems, replace or clean the air filter every 1-3 months. A clogged filter reduces airflow and forces the system to work harder.
- Do not use emergency/auxiliary heat unnecessarily. The "EM HEAT" setting on your thermostat activates backup resistance heating strips, which use 2-3 times more energy. Only use it if the heat pump fails. Set your thermostat's auxiliary heat lockout temperature to the lowest setting your heat pump can handle.
- Lower the thermostat gradually. Heat pumps work most efficiently at steady temperatures. Setback thermostats that drop temperature at night can backfire if the recovery period triggers auxiliary resistance heating. Set nighttime setback to no more than 2-3 degrees.
- Insulate and air-seal your home. Every BTU of heat that escapes through walls, windows, and gaps must be replaced by the heat pump. Air sealing and insulation upgrades reduce the heating load and directly lower energy consumption.