Use your energy supplier app, annual statement or the last 12 months of bills. Enter the unit rates, not the standing charge.
CONSIDERED HOME ENERGY TOOLKIT
Home Energy Investment Calculator
Compare solar panels, home batteries and smart tariffs with investing the same upfront money, using assumptions you control.
Compare the long term value of:
☀ Solar panels
▣ Home batteries
⚡ Smart tariffs
↗ Investing instead
✓ You control every assumption
✓ No installer influences the result
✓ Informed by real-world home energy testing
Built independently by Dale from Considered.
Every result is based on the assumptions you choose. Referral links, partnerships or future services never alter the calculations. This remains an illustration, not financial advice.
Start the calculator
Need help finding your figures? Where to find usage, tariff, solar, battery and cost information
You can begin with estimates and replace them with figures from bills, supplier apps, quotes or warranty documents later.
Check your export tariff agreement or supplier app. This may be with a different company from your import tariff.
Use the array size and annual generation estimate from an installer quote, MCS paperwork or an existing inverter app.
Use the battery's usable capacity, not just its advertised nominal capacity, and the round-trip efficiency from the specification sheet.
Include VAT and unavoidable extras such as scaffolding, electrical work, gateway hardware and DNO-related costs.
Use warranty documents for degradation where possible. Treat energy inflation and investment returns as scenarios, not predictions.
BUILD YOUR SCENARIO
Tell the calculator about your home
Set your energy use, proposed system and future assumptions. The results below update automatically.
YOUR SCENARIO
Assumptions
EXAMPLE STARTING POINTS
Choose a preset / enter your own figures
Presets are starting points, not recommendations. Review every changed value before applying one.
Official baseline: Ofgem's current Typical Domestic Consumption Value is 2,500 kWh of electricity a year. DESNZ's 2024 Great Britain meter statistics report a higher mean because a small number of high-use homes pull the average upward. Lifestyle presets are explicitly illustrative and should be replaced with your own bills or smart-meter data.
Your energy use
Solar system
Battery system
BATTERY SETUP
Choose the closest match
Start with a typical profile, then edit any value that differs from your quote.
Typical 10 kWh battery using more solar in summer and more off-peak charging in winter.
Advanced battery assumptionsCycles, efficiency and custom grid-charging share
Long term assumptions
Optional controls for fine tuning the model. Most people can start with a Future Scenario above.
Investment and timeReturns and projection length
Energy and performancePrice growth and system degradation
Maintenance and replacementOngoing costs and inverter replacement
FUTURE ASSUMPTIONS
Choose the future you want to explore
Pick a starting scenario, then open Advanced assumptions if you want to fine tune the detail.
Advanced assumptions Investment, market, energy price and tariff settings
Explore different futures See how different assumptions change the outcome Scenario Explorer
No one knows exactly what the future holds. Use these settings to explore how different investment returns,
energy prices and tariff changes could influence the long term outcome.
Using a typical global index, smooth returns, the long term UK energy prices trend and a continuing off-peak tariff advantage.
Scenario names describe modelling choices, not forecasts or financial recommendations.
SAVED IN THIS BROWSER
Compare your scenarios
Saved locally on this device. Nothing is uploaded.
YOUR RESULTS
See what your scenario could mean
Start with the headline figures, then use the graph and comparison panels to explore the longer term trade-offs.
READY WHEN YOU ARE
Your results will appear here
Adjust any assumption on the left to model your own home. The comparison, graph and explanation will then update automatically.
Annual electricity use
Solar system size
Battery size
Electricity tariff
YOUR COMPARISON
Your system may repay its cost in 12 years
IF YOU HAD THE UPFRONT MONEY AVAILABLE TODAY
Comparing what the same starting capital might do over 25 years
BUY THE SYSTEM
£0
Energy savings and export income, minus installation, maintenance and replacement costs.
VS
INVEST THE UPFRONT COST
£0
Growth above the original invested capital, before fees and tax.
This comparison assumes a cash purchase using money already available. It does not model loans, finance charges, borrowing costs or keeping the capital aside to pay future energy bills.
WHAT THE MODEL SUGGESTS
The result is sensitive to your assumptions
MORE THAN A FINANCIAL RETURN
The highest projected return is not always the whole answer
Based on long-run historical averages, a diversified index fund may appear to produce a much larger financial return than solar panels or a home battery. That comparison is useful, but it is not a forecast and future market returns may be materially higher or lower.
Solar and batteries provide a different type of value. They can reduce monthly bills, lower exposure to future electricity-price changes, provide a degree of energy independence and, where backup hardware is included, improve resilience during a power cut. Those benefits are real even though they are difficult to express as a single investment return.
An index fund is normally more liquid and has historically offered stronger long term growth, but its value can fall and it does not directly reduce the amount of electricity your home buys from the grid.
The financially optimal choice and the personally valuable choice are not always the same.
SUPPORT CONSIDERED
Help keep useful tools like this free
This calculator is free to use. If it has helped you make a better decision, you can support the research, testing and ongoing development behind Considered in whichever way suits you.
Buy me a coffeeMake a one-off contribution on Ko-fi
↗
Switch to OctopusUse my referral link and view the current offer
↗
Subscribe on YouTubeWatch the testing and future tool updates
↗
Become a memberSupport Considered through YouTube membership
↗
Referral disclosure: some links can financially benefit Considered. They are clearly marked and never change the calculator, its assumptions or its results.
DECISION SUMMARY
Your scenario at a glance
How long the model estimates it could take to recover the upfront cost.
Modelled net financial value over your selected projection period.
Comparing the same starting money with your selected cash savings rate.
Comparing the same starting money with your selected investment return.
WHY THESE RESULTS?
Updating…
HOW SENSITIVE IS THIS RESULT?
Moderately sensitiveThe result depends on assumptions such as future energy prices and investment returns.
ALTERNATIVE USES FOR THE SAME MONEY
What could the same starting capital become?
Compare your home energy system with cash savings and a global index using the assumptions selected below.
Net value created by bill savings and export income after modelled costs.
Illustrative growth using the cash savings rate entered in Long term assumptions.
Illustrative value using the selected investment return and market journey.
Illustrative comparison only. These figures depend entirely on the assumptions you selected. This calculator does not constitute financial advice. Future savings and investment returns may be higher or lower than shown.
Long term comparison
Renewables cumulative net position versus investing the upfront cost.
Renewables
Index fund
Understand the result See what drives the outcome and which assumptions matter most
WHY THIS RESULT?
What is driving your outcome
Generated from the live assumptions and first year value breakdown.
WHAT MATTERS MOST
Your biggest financial influences
The ranking estimates how much a modest change in each assumption affects the long term result.
ABOUT THE INVESTMENT COMPARISON
Explore how the assumptions change the answer
This calculator compares a home energy system with investing the same upfront money elsewhere. It is not a prediction or financial recommendation. Change the expected return under Long term assumptions, or use Explore different futures to test alternative market, energy prices and tariff scenarios.
Higher assumed investment returns naturally favour investing. Higher future energy prices generally strengthen the case for solar and batteries. The purpose is to show how sensitive the decision is to different assumptions, not to claim that one future is certain.
WHERE THE VALUE COMES FROM
Solar and battery contribution in year one
Separating the components helps show whether solar generation, export or tariff shifting is doing most of the work.
Solar-related gross benefit
£0
Direct use, stored solar and export income.
Battery tariff-shifting benefit
£0
Savings from charging cheaply and displacing higher-rate imports.
Estimated first year
- Solar generated
- 0 kWh
- Used directly
- 0 kWh
- Shifted through battery
- 0 kWh
- Exported
- 0 kWh
- Grid charging benefit
- £0
Opportunity cost
- Upfront system cost
- £0
- Index fund ending value
- £0
- Index fund net gain
- £0
- Renewables net gain
- £0
- Savings invested instead
- £0
- Modelled replacements
- £0
ASSUMPTIONS MATTER
A small change can alter the result
How this estimate works
The model estimates direct solar use, solar stored in the battery, exported generation and the benefit of charging part of the battery off-peak. It then applies your assumed price growth, panel degradation, battery degradation, maintenance and replacement costs year by year.
The index comparison compounds the same initial system cost at the annual return you choose. It is not tied to the S&P 500, a UK fund or any named product. The default is only an illustrative starting point, not a forecast or recommendation. The model does not include investment fees, tax or the effect of market volatility.
The model also does not assign a monetary value to reduced grid dependence, greater control over household energy costs, backup capability, environmental benefits, property-value changes or the residual value of the installed system.
Important: battery behaviour is simplified. Real results depend on weather, half-hourly demand, tariff rules, inverter limits, clipping, state-of-charge controls and how intelligently the system is operated.
UNDERSTANDING THE RESULT
Is solar or a home battery worth it in the UK?
There is no single UK-wide answer. Payback depends on the installed price, how much electricity your home uses, when you use it, the import and export tariffs available to you, and how well the system performs. This calculator is designed to make those assumptions visible rather than relying on a generic headline figure.
How is solar panel payback calculated?
A simple solar payback calculation divides the installed cost by the annual financial benefit. The annual benefit normally combines electricity you no longer buy from the grid with payments for exported generation. This tool goes further by changing tariffs, generation, degradation, maintenance and replacement costs over time.
Model solar payback with your figuresAre home batteries worth it without solar?
A battery can potentially save money without solar by charging during a cheaper off-peak window and supplying the home when electricity is more expensive. The result depends on the tariff spread, round-trip losses, usable capacity, achievable cycles and the installed battery price.
Try the battery-only presetIs solar better than investing the money?
Historically, a diversified index fund may show a higher projected financial return. Solar and batteries, however, reduce household bills and can provide some protection from future energy prices changes. They may also provide independence and backup resilience. The best financial projection and the best personal choice are not necessarily identical.
Compare both routes over 25 yearsWhat battery size should I choose?
The largest battery is not automatically the most economical. A battery should be large enough to capture useful surplus solar or cheap-rate electricity, but repeated unused capacity can make payback worse. Start with your half-hourly demand and existing solar-export data where possible.
See where to find your input dataCan a time-of-use tariff improve payback?
It can. A wide difference between off-peak and peak prices can make a battery more valuable, particularly when it can charge cheaply and displace expensive imports. Always check tariff windows, export eligibility, charging limits and current terms before relying on a tariff in a purchase decision.
Change the peak and off-peak ratesWhy compare the options over 25 years?
Solar panels are long-lived assets, so a short payback calculation can miss much of their potential benefit. A 25 year view also exposes uncertainty: equipment may need replacing, tariffs will change, battery capacity may fall and investment returns will vary. Change the assumptions to see how robust the result is.
Read the calculation methodologyCOMMON QUESTIONS
Solar and battery payback questions
How long do solar panels take to pay for themselves in the UK?
It varies significantly. A lower installed price, high self-consumption, expensive imported electricity and a strong export tariff generally shorten payback. Poor orientation, shading, low daytime use or expensive finance can lengthen it. Use your own quote and tariff rather than relying on a national average.
Does the calculator include standing charges?
No. Solar panels and batteries usually do not remove the need for a grid connection, so the standing charge is generally payable with or without the system. It is therefore excluded from the comparison.
Should I use nominal or usable battery capacity?
Use usable capacity. A battery advertised as 10 kWh may reserve part of its nominal capacity to protect the cells, meaning less energy is available for daily charging and discharging.
Are the index fund figures guaranteed?
No. They are scenario projections using the annual return you enter. Historical investment performance does not guarantee future returns, and the model does not include investment fees, tax or short-term market volatility.
Does a battery provide backup during a power cut?
Not automatically. Backup normally requires suitable gateway, isolation and wiring hardware. Confirm the exact backup capability, supported circuits and output limits with the installer before assigning value to resilience.
Can I share my calculation?
Yes. The Share this scenario button creates a URL containing your assumptions. Avoid entering private or identifying information because anyone with that URL can view the scenario.
FOUND THIS USEFUL?
Share it or help fund the next free tool
CONSIDER THE TRADE-OFF
Payback is only one part of the decision
Energy security
Lower bills can reduce your exposure to future tariff changes, even where another investment has a higher expected return.
Liquidity
Money invested in equipment is difficult to access again. An investment account is usually more liquid, but its value can fall.
How you use energy
Two identical systems can produce very different savings because of daytime consumption, export rates and tariff optimisation.