Loading NuWatt Energy...
We use your location to provide localized solar offers and incentives.
We serve MA, NH, CT, RI, ME, VT, NJ, PA, and TX
Loading NuWatt Energy...
NuWatt designs, installs, and manages solar, battery, heat pump, and EV charger systems across 9 states. One company, one warranty, one point of contact.
Get a Free QuoteSimplified Manual J load calculations, balance point analysis, multi-criteria scoring, and fuel cost comparisons — fully transparent.
You enter your address or select your state. The calculator retrieves ASHRAE climate zone, heating degree days (HDD), cooling degree days (CDD), and design temperatures (99% winter design temp, 1% summer design temp) for your area.
You provide square footage, year built, stories, ceiling height, foundation type, insulation quality, window type, air sealing quality, and duct location. Each input maps to engineering parameters: R-values, U-factors, infiltration ACH, and duct loss factors.
Using simplified Manual J, the calculator computes design-day heating load (BTU/h) from wall, ceiling, floor, and window conduction losses plus infiltration losses. Cooling load adds solar gain and latent load factors. Duct losses are applied as a multiplier.
The load is compared against manufacturer capacity data at multiple temperature points (47F, 17F, 5F, -5F). Each heat pump product is scored across 5 dimensions: annual operating cost, comfort (capacity margin), CO2 reduction, cold-climate performance, and cost efficiency. Weights vary by your selected priority (savings, comfort, environment, cold-climate).
You see the top 3 recommended systems with estimated annual savings versus your current system, balance point temperature, installed price range, and available state/utility incentives. A fuel comparison shows current annual costs vs. heat pump costs.
The calculator estimates these values from your inputs. A professional Manual J would measure these directly.
| Parameter | How We Estimate It | Example Value |
|---|---|---|
| Wall R-value | Year built: pre-1950 = R-5, 1970s = R-7, 1990s = R-11, 2000s = R-13, 2010+ = R-19 | 1985 home = R-11 |
| Ceiling R-value | Year built: pre-1950 = R-7, 1970s = R-11, 1990s = R-19, 2000s = R-30, 2010+ = R-49 | 1985 home = R-19 |
| Floor R-value | Foundation type: slab = R-0, crawlspace = R-11, basement = R-10 | Basement = R-10 |
| Window U-factor | Single = 1.1, double = 0.35, triple = 0.22, mixed = 0.55 | Double pane = U-0.35 |
| Infiltration ACH | Air sealing: drafty = 0.75, average = 0.50, tight = 0.35 | Average = 0.50 ACH |
| Duct loss factor | Inside = 1.0x, attic = 1.25x, crawlspace = 1.15x, no ducts = 1.0x | Attic ducts = 1.25x |
| Window area | 15% of floor area (ASHRAE residential default) | 2,000 sqft = 300 sqft windows |
| Insulation adjustment | User quality: poor = -2, average = 0, good = +3, excellent = +6 added to R-values | Good = +3 to wall/ceiling R |
Delta T = 70F (indoor setpoint) - Heating Design Temp
Wall Loss = (1 / Wall R) x Wall Area x Delta T
Ceiling Loss = (1 / Ceiling R) x Ceiling Area x Delta T
Floor Loss = (1 / Floor R) x Floor Area x Delta T
Window Loss = Window U x Window Area x Delta T
Infiltration = 1.08 x CFM x Delta T
where CFM = (Volume x ACH) / 60
Total Heating Load = (Wall + Ceiling + Floor + Window + Infiltration) x Duct Factor
The cooling load uses a similar approach but adds solar gain factor (varies by climate zone: 1.3 for zone 1-2, 0.7 for zone 6-7) and latent load adder (30% in hot-humid zones, 0% in cold zones).
Each heat pump is scored across 5 dimensions. The weights change based on your stated priority.
| Dimension | Savings | Comfort | Environment | Cold-Climate |
|---|---|---|---|---|
| Annual Operating Cost | 40% | 15% | 10% | 20% |
| Comfort (capacity margin) | 10% | 40% | 10% | 15% |
| CO2 Reduction | 10% | 10% | 45% | 10% |
| Cold Performance | 15% | 10% | 10% | 35% |
| Cost Efficiency ($/BTU) | 25% | 25% | 25% | 20% |
| State | Gas ($/therm) | Oil ($/gal) | Propane ($/gal) | Electric ($/kWh) |
|---|---|---|---|---|
| Massachusetts | $1.85 | $4.20 | $3.50 | $0.33 |
| Connecticut | $1.90 | $4.15 | $3.55 | $0.32 |
| Rhode Island | $1.80 | $3.45 | $3.58 | $0.28 |
| New Hampshire | $1.75 | $3.69 | $3.62 | $0.25 |
| Maine | $1.70 | $3.80 | $3.30 | $0.26 |
| Vermont | $1.80 | $4.00 | $3.45 | $0.25 |
| New Jersey | $1.30 | $3.70 | $3.20 | $0.20 |
| Pennsylvania | $1.40 | $3.60 | $3.10 | $0.18 |
| Texas | $1.10 | $3.50 | $2.80 | $0.14 |
Source: EIA State Energy Data System (SEDS) and EIA Heating Oil and Propane Update. Updated quarterly.
A 2,000 sqft home in Massachusetts, built 1985, 2 stories, 8ft ceilings, basement, average insulation, double-pane windows, average air sealing, attic ducts.
A 42,000 BTU/h heating load requires a 3.5-ton (or 48,000 BTU nominal) cold-climate heat pump. Recommended systems would include units with rated capacity at 5F meeting or exceeding the load, with a balance point around 10-15F depending on the specific model.
R-values are estimated from year built, not measured. A professional assessment with blower door test is more accurate and required for most rebate programs.
The calculator sizes for the whole home. Multi-zone ductless systems require room-level load calculations that are beyond this tool.
Homes can have upgraded or degraded insulation versus the age-based defaults. Selecting the insulation quality adjustment helps but does not replace inspection.
The tool includes popular cold-climate models from major manufacturers but does not cover every product on the market.
Duct condition, sizing, and leakage are estimated by location only. Undersized or leaking ducts significantly impact performance.
Oil, propane, and gas prices can fluctuate significantly. Our prices reflect recent EIA averages but your actual costs may differ.
Real Manual J calculations, equipment recommendations, and savings estimates — not a sales pitch. Enter your home details and get results in minutes.
No signup required. No salesperson will call unless you ask.
Answer 5 quick questions and get a personalized heat pump recommendation with balance point analysis and real incentive data.
Go to Heat Pump Calculator