Solar Panels vs Battery Storage
Decide whether to install solar panels or add battery storage first. Get a personalised recommendation based on your existing setup, usage pattern, budget, length of stay, and main goal.
Last updated: April 2026
A solar vs battery storage decision engine compares installing solar PV against adding battery storage based on 5 questions covering existing solar setup, usage pattern, budget, length of stay, and main goal. A 4kW PV system delivers a 6-10 year payback at current tariffs. Businesses embed this tool to capture leads — homeowners reveal budget and energy goals.
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What is Solar vs Battery Decision?
The Solar vs Battery Decision compares the financial and practical case for installing solar PV panels against adding battery storage, for a specific home and usage pattern. Solar panels generate electricity from sunlight during the day, while a battery stores electricity (from solar, off-peak tariffs, or the grid) for use when it is most expensive. The right answer depends on whether you already have solar, when you use electricity, your budget, how long you plan to stay, and your main goal — and for most homes without panels, solar comes first because it generates energy rather than just moving it around.
The Formula
Solar payback (years) = System cost ÷ Annual savings; Battery ROI = (Annual bill savings × lifespan) ÷ Battery cost
Worked Example
A family with an existing 4kW solar PV system (installed 3 years ago) is deciding whether to add a £5,000 home battery to store excess generation. They use around 3,800 kWh per year, most of it in the evening when solar is no longer producing.
- Current position: 4kW solar generates ~3,800 kWh/year; family self-consumes ~30% (1,140 kWh) and exports 2,660 kWh at 15p SEG = £399 export income
- With a 5kWh battery: self-consumption rises to ~70% (2,660 kWh) cutting grid imports by 1,520 kWh at 27p = £410 saved on bills
- But export income falls by £228 (less excess to export), so net gain is £182 per year
- Battery cost: £5,000 installed; expected lifespan: 10-12 years before capacity drops below 80%
- Simple payback: £5,000 ÷ £182 = 27 years — far longer than the battery warranty
- With a time-of-use tariff (Octopus Go, cheap overnight): battery can also arbitrage cheap grid power, improving annual savings to £280-£350 and cutting payback to 14-18 years
📌 For this household, a battery on its own does not pay back within its lifetime at standard tariffs — but combined with a time-of-use tariff and the existing solar system, payback drops to 14-18 years. A household without solar would get dramatically more from spending the same £5,000 on a 4kW solar PV system (6-8 year payback) before ever considering storage. The Energy Saving Trust benchmark confirms this: around 70% of homeowners install solar panels first, and batteries later once they see their actual export/import pattern.
Why This Matters
Solar generates, batteries only shift
Solar panels create new electricity from sunlight — reducing grid imports and generating export income. Batteries store electricity you already have (either from solar or a cheap off-peak tariff), so they only save money by avoiding peak-rate imports. Without solar or a time-of-use tariff, a battery has nothing meaningful to shift, which is why installing solar first almost always delivers a faster payback.
Order matters for cost and payback
Energy Saving Trust data shows 70% of homeowners choose solar first and add battery storage later. Installing solar delivers 6-10 year paybacks at current tariffs because you offset expensive grid electricity (27p+) with free generation. Batteries added on top of solar then extend those savings into the evening — but without solar underneath, batteries rarely pay for themselves within their 10-12 year warranty period.
Your usage pattern changes the answer
A daytime-heavy household (home-workers, retirees) will self-consume 50-60% of their solar directly and may get limited extra value from a battery. A family who is mainly out during the day and home in the evening self-consumes just 20-30% without a battery, so adding storage recovers far more of what would otherwise be exported cheaply — making batteries a much better fit for evening-heavy households with existing solar.
Common Mistakes
❌ Buying a battery before installing solar
Without solar, a battery can only charge from the grid, so it only saves money if you are on a time-of-use tariff (paying 7-15p at night, 27-35p at peak times). Even then, payback is 15-25 years for a £5,000 battery — longer than the warranty. Spend the same money on a 4kW solar PV system first and you typically get a 6-10 year payback instead.
❌ Oversizing the battery for the house
A battery bigger than your typical daily evening use just sits partially full, eating into payback. A family using 8-12 kWh per day needs a 5-7 kWh battery, not 13 kWh. Check your actual evening import on a smart meter for a week before choosing a size — oversized batteries are the most common regret.
❌ Ignoring export income in the maths
Every kWh your battery stores is one less kWh you export to the grid at SEG rates (typically 15-20p/kWh). Battery payback calculations that ignore lost export income can overstate true savings by 40-60%. The real benefit is the gap between your import tariff and your export tariff — typically 10-15p/kWh — not the full import rate.
Industry Benchmarks
| Category | Good | Average | Poor |
|---|---|---|---|
| No existing solar | Install solar first — 6-10 year payback | Battery alone: 15-25 year payback on standard tariff | Battery alone on standard tariff with no solar or EV |
| Existing solar, evening-heavy use | Add battery: 10-14 year payback with time-of-use tariff | Battery + solar: 14-18 year payback on standard tariff | Oversized battery beyond daily evening need |
| Combined new install (solar + battery) | 8-12 year combined payback with 60-80% self-consumption | 12-15 year combined payback | Over 15 years — likely over-specified |
Source: Energy Saving Trust
Benchmark data sourced from Energy Saving Trust.
From analysing embed performance across hundreds of websites, businesses that replace static forms with interactive tools like this one see 3-5x more qualified leads — visitors volunteer their data because they get personalised results in return.
One of the most common mistakes we see when working with clients: buying a battery before installing solar. Without solar, a battery can only charge from the grid, so it only saves money if you are on a time-of-use tariff (paying 7-15p at night, 27-35p at peak times). Even then, payback is 15-25 years for a £5,000 battery — longer than the warranty. Spend the same money on a 4kW solar PV system first and you typically get a 6-10 year payback instead.
Embed This Decision Engine on Your Website
Every visitor who uses your embedded decision engine becomes a qualified lead. Their inputs, results, and business data are captured and sent to your CRM — before you ever pick up the phone.
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