Can Solar Panels Reduce Your Electricity Bill by 70%?

Solar panels are often sold on bold claims about how much they'll cut your electricity bill, and 70% is one of the numbers that comes up most.

For some households, a 70% reduction in their electricity bill is genuinely achievable. For most, a more realistic first-year outcome sits somewhere between 30% and 55%.

The gap between those two answers comes down to one thing more than any other: how much of the electricity your panels generate you actually use yourself, rather than exporting it back to the grid.

How do solar panels reduce electricity bills?

Here's the maths behind it, so you can work out where your own home is likely to land and if solar panels are worth the investment.

What "bill reduction" actually means

It's worth being precise about what's being measured, because this is where a lot of confusion creeps in.

Your bill reduction is the share of your total annual electricity consumption that you cover using self-generated solar power, rather than buying from the grid. Electricity you export through the Smart Export Guarantee (SEG) is separate: it's income, not a reduction in what you'd otherwise have paid.

The formula, in simple terms:

Bill reduction (%) = (solar electricity used directly at home ÷ total annual electricity consumption) × 100

Two numbers drive that result: how much your system generates relative to your usage, and what share of that generation you manage to use yourself rather than send back to the grid.

An example of savings without a battery

Take a household using the UK average of around 3,400 kWh a year, with a well-positioned 4.5kWp system generating somewhere in the region of 3,800 to 4,200 kWh annually, depending on orientation and shading.

solar-hands-air

Without a battery, typical self-consumption for a household that's out during the day runs at roughly 35% to 50% of what the panels generate, since most solar electricity arrives at midday when nobody's home to use it.

At 40% self-consumption of, say, 4,000 kWh generated, that's 1,600 kWh used directly. Against 3,400 kWh of total consumption, that works out to a bill reduction of around 47%.

This is an illustrative example, not a quote. Your own figures will depend on your actual usage, roof and system size.

An example of savings with a battery

Add a solar battery to the same system, and self-consumption typically rises substantially, since surplus daytime generation gets stored rather than exported, and used in the evening instead. A well-sized battery can push self-consumption to 65% or more of total generation for many households.

At 65% self-consumption of 4,000 kWh generated, that's 2,600 kWh used directly. Against the same 3,400 kWh of annual consumption, that's a bill reduction of around 76%.

You might like this guide: How much do solar panels with a battery cost in the UK?

What has to be true for you to get close to 70%

Your system needs to be sized close to your usage

If your system generates far less than you consume annually, even 100% self-consumption won't get you close to 70%, since there simply isn't enough solar electricity being produced.

If it generates far more than you use, you'll hit a ceiling on self-consumption regardless of a battery, because there's only so much you can use or store before the rest has to be exported.

You need high self-consumption, which usually means a battery

This is the single biggest lever. Without storage, most households simply aren't home to use midday generation, and a large share gets exported at the (lower) SEG rate rather than offsetting a bill.

Your roof needs decent orientation and minimal shading

A shaded or poorly oriented roof can cut annual generation significantly before self-consumption even enters the equation. Our guide on how solar panels work explains how orientation and shading affect output.

Your usage pattern matters too

Households that can shift some usage into daylight hours, running the washing machine, dishwasher or an EV charger while the sun's out, naturally push self-consumption higher without needing a larger system.

This is exactly what the Energy Saving Trust's own published case study demonstrates: one homeowner, Terry, reported that from mid-March to mid-October, his household barely buys any grid electricity at all, with one August bill totalling just 79p. His system was originally predicted to cut bills by around 10%, but a battery added a few years later transformed the outcome, since it captured surplus daytime generation that would otherwise have been exported.

What about export payments?

Any solar electricity you generate but don't use gets exported to the grid, and under the Smart Export Guarantee, licensed suppliers are required to pay you for it, provided your system was fitted by an MCS-certified installer.

solar-roof

This is worth having regardless of your self-consumption rate, but it's a separate income stream on top of your bill reduction, not a way of inflating the percentage.

So, is a 70% reduction realistic for you?

It depends less on the brand of panel you choose and more on three things:

Whether your system is sized to your actual usage
Whether you have a battery
How much of your daily routine happens during daylight hours.

Get those broadly right, and 70% is a genuinely achievable outcome rather than an exaggerated headline. Get them wrong, and a well-installed system might still land closer to 30% to 40%, which is still a meaningful saving.

The only way to know where your own home sits is to run the numbers against your actual usage. Our solar panel savings calculator gives you an indicative estimate in under a minute.