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Solar + HVAC Combo Calculator

Bundle solar panels and a heat pump for maximum tax credits. Enter home size, climate zone, and system specs — get combined ITC + 25C credits and payback.

Home & system details
sqft
yrs
tons
kWp
Combined federal tax credit
$10,980 in credits
Solar ITC (30%)$8,400
Heat pump 25C credit$1,980
Panel upgrade credit$600
Total system cost$34,132
Net after credits$23,152
Electrification load shift12,390 kWh/yr
Annual savings (elec + gas)$1,983/yr
Install comparison
Bundled install (net after credits)$23,152 — 11.7 yr payback
Separate installs (net after credits)$26,120 — 13.2 yr payback
Bundled saves $2,968 on installation vs separate
20-year NPV: $13,619
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How to Use This Calculator

Enter your home and climate details

Start with your conditioned floor area in square feet — this determines your HVAC load. Select your DOE climate zone, which ranges from Zone 1 (very hot, Miami/Phoenix) to Zone 7 (very cold, Alaska/northern Minnesota). Climate zone is the single biggest factor in how much heating and cooling energy your heat pump will use. Enter your existing HVAC system's age — systems over 15 years are near end of life and replacement timing is ideal for bundling with solar.

Enter your system specifications

Enter the heat pump size in tons (1 ton = 12,000 BTU/hr; rule of thumb is 1 ton per 600 sqft in moderate climates). Enter your planned solar PV system size in kilowatts-peak. Toggle Section 25C eligibility — the IRA's residential energy efficiency tax credit applies to qualifying heat pump installations through 2032, providing up to $2,000 in federal tax credit for the heat pump plus up to $600 for an electrical panel upgrade.

Read the bundled vs separate comparison

The calculator shows the combined federal tax credit stack (30% solar ITC + 25C heat pump + panel credit), the bundled installation discount vs buying separately, total payback period, and 20-year net present value. The bundled savings reflect shared labor costs, a single permit pull, and the installer's volume discount on equipment when both systems are installed together.

The Formula

HVAC Load = sqft × zone heat factor × 4.5 kWh + sqft × zone cool factor × 3.0 kWh PV Annual kWh = kWp × 4.5 PSH × 365 × 0.80 Solar ITC = PV System Cost × 0.30 Heat Pump 25C = min(HP Cost × 0.30, $2,000) Panel Credit = min(Panel Cost × 0.30, $600) Bundled Discount = 8% of total system cost Annual Savings = Electricity Savings + Gas Offset Savings Payback = (Net Cost After Credits) ÷ Annual Savings 20-yr NPV = −Net Cost + Σ(Annual Savings × 1.025^yr ÷ 1.03^yr)

The 8% bundled discount reflects real-world savings from combined permitting, shared scaffolding/access, one electrical panel tie-in, and installer volume purchasing. The 20-year NPV uses a 3% discount rate with 2.5% annual utility escalation — a conservative but realistic projection based on EIA historical data.

Example

The Hendersons — Gas furnace → heat pump + solar in Climate Zone 4

The Hendersons have a 2,000 sqft home in Washington DC (Zone 4) with a 15-year-old gas furnace. They're replacing it with a 3-ton heat pump and installing 10 kWp of solar simultaneously. They qualify for Section 25C.

Home2,000 sqft, Zone 4
Heat pump3-ton (36,000 BTU/hr)
Solar PV10 kWp
25C eligibleYes

Result

Solar ITC (30%)$8,400
Heat pump 25C credit$2,000
Panel upgrade credit$600
Total credits$11,000
Bundled install saves~$2,200 vs separate
Payback (bundled)~8.5 years
20-year NPV+$28,000

The Hendersons benefit from stacking three separate federal credits in a single year. The key insight is that Section 25C and the solar ITC come from different budget buckets — you can claim both in the same tax year. Bundling also captures the shared-labor discount that disappears when projects are done separately.

FAQ

Yes — the solar Investment Tax Credit (ITC, 30% through 2032) and the Section 25C Residential Clean Energy Property Credit (up to $2,000 for qualifying heat pumps) are separate credits from different sections of the tax code. You can claim both in the same tax year. Additionally, the Section 25D credit ($600 cap) applies to electrical panel upgrades required to support the heat pump or EV charger. Consult a tax professional to confirm your specific situation, especially if you have tax liability limitations.
Bundling typically saves 5–12% of total project cost through: shared permit and inspection fees (one permit pull instead of two), shared electrical panel work, shared crane or roof access equipment, shared project management overhead, and installer volume pricing on equipment. On a $30,000 combined project, this equates to $1,500–3,600 in savings. The tax credit timing is also beneficial — the 30% solar ITC applies to the full solar system cost, which may include EV charging wiring if installed simultaneously.
A proper Manual J load calculation from a licensed HVAC contractor is the only accurate way to size a heat pump. As a rough estimate: 1 ton per 600 sqft in Zones 1–3 (mild climates), 1 ton per 500 sqft in Zone 4, 1 ton per 400 sqft in Zones 5–7 (cold climates). Cold-climate heat pumps (rated to -13°F or lower) like the Mitsubishi Hyper Heat or Bosch IDS can handle Zones 5–7 without a backup. Oversizing reduces efficiency; undersizing leaves you cold. The calculator uses a zone-adjusted estimate — get a quote for the actual Manual J.
Not always — it depends on your gas vs electricity cost ratio. Heat pumps are 2–4× more efficient than gas furnaces, but if your electricity rate is 3× your gas rate on a per-BTU basis, efficiency gains are erased. The breakeven ratio is roughly: electricity rate in $/kWh ÷ gas rate in $/therm × 29.3 should be less than your heat pump's COP (typically 2.5–4). In most US states with electricity at $0.13–0.18/kWh and gas at $0.80–1.20/therm, heat pumps win. In states with cheap gas (Louisiana, Oklahoma) and expensive electricity, gas remains competitive.
Adding a heat pump increases your electricity consumption by 30–60% (replacing gas loads with electric ones), so you need a proportionally larger solar system. A 2,000 sqft home in Zone 4 might currently use 9,000 kWh/year for all electric loads. Adding a heat pump for heating adds 4,000–6,000 kWh/year — increasing total load to 13,000–15,000 kWh/year. At 4.5 peak sun hours and 80% system efficiency, you'd need a 10–12 kWp solar system to offset the combined load. Always size solar for your post-electrification consumption, not your current bill.

Related Calculators

🌡️ Solar Heat Pump Size
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💰 Solar Tax Credit Calculator
Calculate your federal ITC, state credits, and Section 25C heat pump credit.
☀️ Solar Panel Calculator
How many panels to cover your total home electricity load including HVAC.
📈 Solar ROI Calculator
Full 25-year ROI model with escalating utility rates and degradation.

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