The Heat Pump Decision Journey
Should I replace my boiler with a heat pump?
From understanding heat demand to comparing lifetime running cost against your current boiler — six steps that translate manufacturer datasheets into your actual bill.
What you'll have at the end
A clear view of realistic seasonal efficiency, annual running cost, payback vs your current heating, and lifetime CO₂ reduction.
The Journey
- 1
Step 1 — Guide
How much heat does my home actually need?
Understand heat demand
A well-insulated home needs roughly 30–50 W/m² at design temperature; poorly insulated homes need 60–100 W/m². This drives correct sizing.
Read heat demand basics→ Then continue to step 2 - 2
Step 2 — Guide
What SCOP is realistic for my system?
Estimate seasonal efficiency
Datasheets quote COP at ideal conditions. Real-world SCOP depends on flow temperature and climate: 3.8–4.5 for low-temp systems, 2.8–3.4 for retrofit radiators.
Learn COP vs SCOP→ Then continue to step 3 - 3
Step 3 — Calculator
What will it cost me to run each year?
Compare against your boiler
Divide annual heat demand by SCOP, multiply by your electricity price, compare against gas/oil/LPG or resistive electric. This is the real bill.
Open Savings Calculator→ Then continue to step 4 - 4
Step 4 — Calculator
What's my payback vs current heating?
Calculate payback
Compare installed cost minus grants against annual savings. Typical payback is 6–14 years depending on fuel type replaced and electricity tariff.
See payback breakdown→ Then continue to step 5 - 5
Step 5 — Calculator
Can I run it partly on solar?
Pair with rooftop solar
A heat pump's summer domestic hot water load overlaps well with solar output. Winter heat demand does not — but a battery or smart tariff can shift consumption.
Explore solar synergy→ Then continue to step 6 - 6
Step 6 — Calculator
How much CO₂ will I save?
Verify emissions reduction
Compare tonnes of CO₂ from your current fossil fuel against grid electricity ÷ SCOP. Most European grids yield 60–85% CO₂ reduction; cleanest grids exceed 90%.
Decision Summary
Heat Pump Assessment
Medium confidence- Realistic SCOP
- 2.8–4.5
- Annual savings vs gas
- $300–$900
- Annual savings vs oil/LPG
- $800–$1,800
- Simple payback
- 6–14 years
- CO₂ reduction
- 60–90%
Depends on flow temperature & climate
At typical European tariffs
After grants, vs fossil boiler
Vs your existing fossil boiler
Recommended next step
Get an MCS/EN 14511 heat loss survey before quoting installers. If radiators need flow above 55°C, budget for one or two upgrades to keep SCOP above 3.2.
Why this confidence level
Running cost is highly sensitive to real-world SCOP and your electricity-to-gas price ratio — both vary by country and tariff.
Assumptions: Numbers assume a well-installed air-source heat pump with weather compensation, sized to your heat loss.
Journey complete
You now have the numbers to decide.
Save your results, take them to installer quotes, and revisit the calculators any time your inputs change. Every formula on this site is documented, every assumption editable — no black box.
Explore more heat pumps guides
Continue with another journey
Household energy decisions are interconnected. The solar payback you just calculated feeds into the heat pump running cost, which feeds into your EV charging cost. Each journey below picks up where the last left off.