The Solar Decision Journey
Should I install solar on my home?
A five-step path from "how much roof do I have?" to "what's my 25-year return?" — using the same calculators an installer would use, but with editable assumptions.
What you'll have at the end
A defensible answer on system size, payback period, lifetime savings and CO₂ avoided — enough to negotiate installer quotes with confidence.
The Journey
- 1
Step 1 — Guide
How much usable roof area do I have?
Measure your roof
Solar sizing starts with roof area. A 5 kWp system needs roughly 24 m² (260 ft²) of unshaded, south-facing roof. Convert ft² to m² if your quotes mix units.
Convert roof area→ Then continue to step 2 - 2
Step 2 — Guide
How much energy will my system produce?
Estimate annual output
Understand kWh per kWp for your latitude, panel orientation, and losses. Northern Europe yields 850–1,300 kWh/kWp/year; Southern Europe reaches 1,600–1,800.
Read output guide→ Then continue to step 3 - 3
Step 3 — Guide
Do I need a home battery?
Size battery storage
A battery lifts solar self-consumption from ~30% to 60–80% — but only pays back where retail electricity is much dearer than export tariffs. Learn the trade-off.
Read battery guide→ Then continue to step 4 - 4
Step 4 — Calculator
What's my payback period and lifetime return?
Calculate solar payback
Model year-by-year cash flow with degradation, inflation and self-consumption. Get simple payback, 25-year net return, LCOE and CO₂ avoided.
Open Payback Calculator→ Then continue to step 5 - 5
Step 5 — Calculator
How much CO₂ am I actually avoiding?
Verify climate impact
Multiply annual kWh generated by your grid CO₂ intensity to see tonnes of CO₂ displaced over the panel lifetime — the number that matters beyond the money.
Decision Summary
Solar Assessment
High confidence- Typical system size
- 5–8 kWp
- Annual savings
- $900–$1,600
- Simple payback
- 7–10 years
- 25-year net return
- $22,000–$36,000
- CO₂ avoided
- 2.5–4.5 t/year
For a 3–4 person European household
Bill offset + export income
Post-grant, at current tariffs
After degradation & inflation
Depends on your grid mix
Recommended next step
If self-consumption is below 40%, model a 5–10 kWh battery. If payback is under 8 years, get three installer quotes this month.
Why this confidence level
Solar economics are well-understood — the main uncertainty is your future electricity tariff, not the technology.
Assumptions: Numbers assume unshaded south-facing roof, 0.5%/year degradation, 3% electricity price inflation, and standard European feed-in tariffs.
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 solar energy 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.